Arctic Sea Ice : Forum

Cryosphere => Arctic sea ice => Topic started by: Tom_Mazanec on April 01, 2020, 12:59:14 PM

Title: Tides
Post by: Tom_Mazanec on April 01, 2020, 12:59:14 PM
Here you are, oren.
Do tides affect currents and sea ice?
Title: Re: Tides
Post by: blumenkraft on April 01, 2020, 01:23:24 PM
Interested people on the topic might find comprehensive GIFs in the RAMMB-SLIDER thread.

This one for example >> https://forum.arctic-sea-ice.net/index.php/topic,2649.msg244558.html#msg244558
Title: Re: Tides
Post by: uniquorn on April 01, 2020, 01:29:40 PM
When the tide goes up, where does the water at the bottom come from?
Title: Re: Tides
Post by: kassy on April 01, 2020, 01:40:41 PM
The effects of tides on the water mass mixing and sea ice in the Arctic Ocean

Abstract
In this study, we use a novel pan‐Arctic sea ice‐ocean coupled model to examine the effects of tides on sea ice and the mixing of water masses. Two 30 year simulations were performed: one with explicitly resolved tides and the other without any tidal dynamics. We find that the tides are responsible for a ∼15% reduction in the volume of sea ice during the last decade and a redistribution of salinity, with surface salinity in the case with tides being on average ∼1.0–1.8 practical salinity units (PSU) higher than without tides. The ice volume trend in the two simulations also differs: −2.09 × 103 km3/decade without tides and −2.49 × 103 km3/decade with tides, the latter being closer to the trend of −2.58 × 103 km3/decade in the PIOMAS model, which assimilates SST and ice concentration.

The three following mechanisms of tidal interaction appear to be significant:
(a) strong shear stresses generated by the baroclinic clockwise rotating component of tidal currents in the interior waters;

(b) thicker subsurface ice‐ocean and bottom boundary layers; and

(c) intensification of quasi‐steady vertical motions of isopycnals (by ∼50%) through enhanced bottom Ekman pumping and stretching of relative vorticity over rough bottom topography. The combination of these effects leads to entrainment of warm Atlantic Waters into the colder and fresher surface waters, supporting the melting of the overlying ice.

...

Since continental shelves make up approximately 50% of the AO area, shelf‐sea processes (such as ocean tides, land‐fast ice‐ocean interactions, coastal currents, downslope cascading, up/downwelling, and eddies) [Nurser and Bacon, 2014] have a substantial influence on the entire AO. These processes are generally not accounted for in either global or regional Arctic models, which do not have sufficiently fine horizontal meshes to resolve the required physical scales and sufficiently high vertical resolution to accurately simulate surface and benthic boundary layers. At present, none of the coupled ocean‐atmosphere general circulation models (OA‐GCMs) used in IPCC AR5 and only a few of the global or pan‐Arctic models participating in the Forum for Arctic Ocean Modeling and Observational Synthesis (FAMOS; http://www.whoi.edu/projects/famos/overview) have sufficient resolution to account for shelf‐sea physical processes.

...

Astronomical tides are strong on the Arctic shelf with M2 amplitudes reaching 4.4 m in the Hudson Strait, 2–3 m in the White Sea and >1 m in the Canadian Archipelago (for geographical names see Figure 1). Holloway and Proshutinsky [2007] reviewed the observational and modeling evidence for the role of tides in the Arctic and presented arguments on why the “omission of tides from climate modeling can be particularly troubling.” They hypothesized that tidal‐induced mixing in the AO plays an important role in the global conveyer belt. Holloway and Proshutinsky [2007] included a parameterization of tidal mixing near‐bottom topography and tidal‐induced divergence‐convergence of ice in a coarse resolution (55 km) coupled ocean‐ice general circulation model, and compared the results with and without tides on decadal time scales. Tidal currents in their study were derived from a barotropic ocean‐ice coupled model with a grid spacing of 14 km [Kowalik and Proshutinsky, 1993, 1994]. The authors showed that the regions of strongest tidal dissipation are located along the western opening to the Barents Sea, above Yermak Plateau and over Eurasian continental shelf slopes in the Barents, Kara and Laptev Seas, thus mapping well onto the pathway of the Atlantic Water (AW) inflow in the AO. They suggested that tides can result in AW ventilation and modification via the mixing of this water mass with overlying polar waters, affecting the Arctic extension of the conveyer belt and potentially changing the Arctic and global climate.

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2014JC010310

Open access , have not looked into linked articles.
Note that AO here is just short for Arctic Ocean.
Title: Re: Tides
Post by: blumenkraft on April 01, 2020, 02:06:14 PM
The impact of ocean bottom morphology on the modelling of the long gravity waves, from tides and tsunami to climate

Abstract

Quote
Ocean basin morphology is a major controlling parameter of the ocean dynamics. We address here its impact on long gravity waves: tsunamis, storm surges and tides. The deterministic character of the tides allows one to easily illustrate how modelling of long gravity wave in the ocean is dependant upon the knowledge of the shape and depth of the ocean basins, and on the slope of seamounts, mid ocean ridges and continental shelf breaks. A few examples are given. The first one is the impact of inaccuracies in the bathymetry on wave propagation at basin scale (the North Atlantic). The second one shows the global dependency of the solutions (the remote effect of the resolution of the tides under the Weddel Sea permanent ice shelf). The third one illustrates the trapping of energy by the continental slopes above the critical latitudes (the diurnal tides over the Yermak plateau). Particular focus is given on the importance of the energy transfer from barotropic tides to baroclinic internal waves. This transfer is taking place over seamounts, mid ocean ridges and at the shelf breaks, closely dependent upon the slope of the bathymetry. This energy transfer to internal wave could play a role on the deep ocean mixing, contributing to the maintenance of the thermohaline circulation, and hence impacting the climate of the earth.

Link >> https://www.gebco.net/about_us/presentations_and_publications/documents/cen_conf_abstract_le_provost.pdf
Title: Re: Tides
Post by: blumenkraft on April 01, 2020, 02:35:46 PM
Quote
In the Arctic sea-ice pack, ice motion is largely a response to local winds and ocean currents (including tides)

Link >> https://www.cambridge.org/core/journals/journal-of-glaciology/article/meso-and-microscale-seaice-motion-in-the-east-siberian-sea-as-determined-from-ers1-sar-data/E0A7D4458296C2D4D0F6A331436EC69D/core-reader
Title: Re: Tides
Post by: tybeedave on April 01, 2020, 04:38:32 PM
ty kassy,

 for backing up, with real evidence, my feeling that tides could influence the melting of Arctic ice in the Nares and throughout the Arctic.

to those who say ' show me where it says', consider yourself as having been shown....

great work, kassy !!!

td
Title: Re: Tides
Post by: kassy on April 01, 2020, 09:33:14 PM
Actually i know very little about it but it piqued my interest. Next step then is a bit googling to find out what the science says.  ;)
Title: Re: Tides
Post by: Tor Bejnar on April 02, 2020, 05:06:21 AM
...
Abstract
...
simulations also differs: −2.09 x 103 km3/decade without tides and −2.49 × 103 km3/decade
...
I hope you all know that "x 103 km3" means "x 103 km3".
Title: Re: Tides
Post by: blumenkraft on April 02, 2020, 06:39:31 AM
The forum even has a button for that. People should use it!
Title: Re: Tides
Post by: binntho on April 02, 2020, 07:38:09 AM
When the tide goes up, where does the water at the bottom come from?

Yes, uniqorn. You are here expressing one of the fundamental misunderstandings of how tidal waves (and pressure waves for that matter also) actually function.

The tide goes up because the water column expands due to changes in pressure, with the change in pressure being caused by gravitational changes.

Same happens when changes in atmospheric pressure cause corresponding changes in sea surface (appr. 1 cm per millibar, see here (https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/96JC02920)). Whithin the Northern Atlantic and the Arctic, differences in atmospheric pressure from one place to another can easily exceed 50 mbar, leading to a difference in sea level of half a metre. Again, this is due to expansion and contraction of the water column.

Sea level rise due to the tidal effect is usally at the same or smaller scale as this, with localized exceptions (e.g. south of Iceland and along the European Atlantic seabord, where in excess of 1 metre can be seen).

But  most of the world's oceans only see a tidal fluctuation of less than 50 cm, see here (https://en.wikipedia.org/wiki/Tidal_range#/media/File:M2_tidal_constituent.jpg).

EDIT: Expanded slightly.
Title: Re: Tides
Post by: binntho on April 02, 2020, 07:40:42 AM
ty kassy,

 for backing up, with real evidence, my feeling that tides could influence the melting of Arctic ice in the Nares and throughout the Arctic.

to those who say ' show me where it says', consider yourself as having been shown....

great work, kassy !!!

td

Yes, thanks Kassy. I've read several similar papers. Not one of them supports claims such as the one that set off the current debate: That changes in Fram export that we have seen over the last months are somehow linked to phases of the moon.
Title: Re: Tides
Post by: binntho on April 02, 2020, 07:44:05 AM
Quote
In the Arctic sea-ice pack, ice motion is largely a response to local winds and ocean currents (including tides)

Link >> https://www.cambridge.org/core/journals/journal-of-glaciology/article/meso-and-microscale-seaice-motion-in-the-east-siberian-sea-as-determined-from-ers1-sar-data/E0A7D4458296C2D4D0F6A331436EC69D/core-reader

Yes blumenkraft. I've read similar papers online. None of them supports claims such that Fram export can change in accordance to the phases of the mooon.

I'd like to point out what I wrote yesterday:

HOWEVER!!!!!

Long-term movements of ocean currents ARE effected by the tidal pull of the moon. So the effect is not non-existent in the open ocean, but it is NOT a fluctuating effect. In other words, no research i've found indicates that changes in tidal movement on a daily or monthly basis has any discernible effect.

The existence of tides has a constant effect, not a fluctuating effect, changes in the tides on a daily or monthly  basis does not effect the large scale state of the ice in the Arctic Ocean.
Title: Re: Tides
Post by: binntho on April 02, 2020, 07:56:04 AM
Moving on from my last post: Of course, as any pedant can point out, the long-term tidal effects are due to the fluctuating nature of the tides.

But in the large scale of things, these fluctuations have almost no impact per se. It is the cumulative impact that is real, but the impact of indivual tidal movement is purely local and temporal, with any movement being almost exclusively up-and-down and back-and-forth, so the net effect is usually zero.

Some people have the pet ideas that they can somehow predict (or explain) daily, weekly or monthly changes in the large scale behaviour of Arctic sea ice by referring to the phases of the moon. Every such claim is unsubtantiated by both basic science and current scientific research.
Title: Re: Tides
Post by: binntho on April 02, 2020, 08:12:18 AM
blumenkraft has sent me a private message taking umbrage at my lack of acceptance of silly claims such that changes in Fram export can be caused by changes in the phases of the moon. Well bless him, but I guess our tempers collective and individual are not what they should be now, these corona virus times!
Title: Re: Tides
Post by: blumenkraft on April 02, 2020, 08:21:38 AM
Full disclosure, this is what i wrote:

Quote
You might try reading what people post!

You wasted too much of my time for you already. I googled those papers for you clearly stating that tidal forces have a crucial role to play here. I linked the GIF for you so that you can see what tidal forces do to the ice by smashing them into small pieces.

It all went down the drain.

And now you have the nerve telling me i should read your wall of text? A wall of text that says absolutely nothing?

How dare you?

Please, stop derailing the melting thread any further with this bogus.
Title: Re: Tides
Post by: binntho on April 02, 2020, 08:29:14 AM
Full disclosure, this is what i wrote:

Thank you. First I'd like to say that I am not the best at reading what other people write! So cricising you for that was somewhat hypocritical.

I'd like to refer you to uniqorn's "where does the water come from" comment above. Even the best and most valuable of members, that have been providing the rest of us with a constant and positive input (such as yourself) can be totally off when it comes to such basic scientific facts as what a pressure wave actually is.

That is why I dare! Because none of us knows all, but some of us have a better basic understanding of physics than others. This basic understanding can of course lead you into the briar patch, but when something jars against it, I not only dare to respond, but I do.

So silly claims, such as that the phases of the moon can effect Fram export, will be bashed by me now and in the future.
Title: Re: Tides
Post by: SteveMDFP on April 02, 2020, 08:54:46 AM

The tide goes up because the water column expands due to changes in pressure, with the change in pressure being caused by gravitational changes.

I don't think this makes sense.  Water is an almost totally incomprehensible substance. Subject a column of water in a laboratory to immense pressure, and the change in volume is negligible.
Title: Re: Tides
Post by: interstitial on April 02, 2020, 09:16:16 AM
waves on the ocean are not pressure waves.
Pressure waves travel through the medium not on top of it. Sound is a pressure wave.
The wave motion on a body of water is not a tide. The motion of water on the surface is a displacement wave. The displacement wave moves water up and down but does not move water towards the shore or away from the shore.


waves are a transference of energy not matter. Yes the move the matter locally but not very far and the net affect is not motion.


Tides flow in increasing the local water depth. This is not a wave it is a large increase in the amount of water in a region. It is caused by gravity but it is the moons gravity that causes a bulge in the ocean on the side closest to the moon and a deficit elsewhere.


This disagreement can be summed up as


1.wave does not equal tide


2.wave is movement of energy


3.tide is movement of water.

Title: Re: Tides
Post by: interstitial on April 02, 2020, 09:54:46 AM
My point is still valid but for clarity i didn't use the correct terms.


A pressure wave is a longitudinal wave. In a longitudinal wave displacement of particles is parallel to direction of wave travel. Net motion of particles averages to zero. longitudinal waves travel through a medium. Example a sound wave.


A transverse wave has particle displacement perpendicular to the direction of travel. Net motion of particles also averages to zero. Transverse waves travel on the surface of the medium. Example a ripple on water
Title: Re: Tides
Post by: uniquorn on April 02, 2020, 12:49:13 PM
When the tide goes up, where does the water at the bottom come from?
Yes, uniqorn. You are here expressing one of the fundamental misunderstandings of how tidal waves (and pressure waves for that matter also) actually function.
The tide goes up because the water column expands due to changes in pressure, with the change in pressure being caused by gravitational changes.

Sea level rise due to the tidal effect is usally at the same or smaller scale as this, with localized exceptions (e.g. south of Iceland and along the European Atlantic seabord, where in excess of 1 metre can be seen).
But  most of the world's oceans only see a tidal fluctuation of less than 50 cm, see here (https://en.wikipedia.org/wiki/Tidal_range#/media/File:M2_tidal_constituent.jpg).
EDIT: Expanded slightly.
That is certainly not the answer I was expecting and your link doesn't provide any scientific evidence for the proposition.

I propose that tidal induced lateral movement can be caused over areas where there is a change in ocean depth. The coast being a special, easily observable, case where depth tends to zero.  Consider an area where ocean depth increases rapidly from 200m to 3000m. Does the water simply go up and down in a straight line with the tides? It is more likely to cause turbulence in the form of eddies or internal standing waves, mixing the water and, if there is sea ice on the surface, causing some of it to melt. 

https://gyre.umeoce.maine.edu/physicalocean/Tomczak/ShelfCoast/notes/chapter05.html
Quote
Tides in shallow seas
This very brief summary of tidal dynamics in deep water is still quite incomplete, but it is sufficient to understand the action of the tides on shelves and in estuaries. The first and fundamental observation with respect to tides in shallow water is that the tide-generating force is of global scale. Only the largest water bodies such as the major oceans can therefore experience tidal forcing in the way described by Laplace. Smaller water bodies such as marginal seas or estuaries cannot produce a response to astronomical tidal forcing. If there is tidal movement in these regions, it is forced by the tidal currents of the deep ocean which enter and leave the region periodically at the connection to the ocean. Tides generated in this way are known as co-oscillation tides. Marginal seas have their own resonance frequencies, determined again by their dimensions. As a consequence, the amplitudes and phases of co-oscillation tides depend on the closeness of a resonance frequency to one of the tidal frequencies and on the amplitude of the tidal currents in the deep ocean at the connecting line with the marginal sea. This explains, for example, why mediterranean seas are virtually tide-free; their connection with the open ocean is so restricted that the oceanic tides cannot produce co-oscillation.

Because co-oscillation tides are a resonance phenomenon they usually display the largest tidal range near the coast of the marginal sea or at the inner end of a bay. (You can see this demonstrated in an animation.) This can give rise to extreme tidal ranges if the co-oscillation occurs at resonance. The largest tidal range occurs in the Bay of Funday on the Canadian Atlantic coast. This bay is 151 km long and 31 km wide and at spring tide experiences a tidal range of 21 m. The North West Shelf of Australia is another region with large tidal resonance; the tidal range on the North West Shelf reaches 8 m and more.

A large tidal range is of course always associated with strong tidal currents, and tidal currents on the shelf are always larger than tidal currents in the open ocean. In some locations tidal currents can become unusually strong even under a moderate or small tidal range. This occurs where constrictions prevent the free flow of the tidal wave and force it to rush through narrow openings.

The most spectacular tidal current of this type is the famous "maelstrom" in the Saltfjord of northern Norway. This 500 m deep fjord is connected with the North Atlantic Ocean by a 3 km long channel of only 150 m width and 31 m depth. The channel is much too small to allow the fjord to follow the oceanic tide, and the difference in water level between the two ends of the channel can reach up to 1 m. This produces a periodic current through the channel of speeds in excess of 20 knots (up to 40 km/h) which produces intense whirlpools (maelstroms) of 10 - 15 m diameter. Calm conditions every 6 hours allow ships to pass through the channel, before the current starts again. For centuries it has been said that the Saltstraumen, as the current is known, runs strongest on Good Friday (the Friday before Easter). This is easily understood from tidal theory if we recall that the Christian church sets the date of Easter as the first Sunday after the full moon following the vernal equinox: By definition the tide generating potential of the sun and moon act in concert at that time.

A coastal inlet in the Kimberleys of Western Australia shows even stronger tidal currents. Its connection to the North West Shelf is only a few hundred meters long and barely 50 m wide. The difference in water level on either side of the connection is clearly visible from the top of the cliff, as a tidal waterfall rushes through the gap, changing direction every six hours.

Shallow seas which are close to resonance with one of the tidal periods are of great importance for the world's fishing industry. The flow of strong tidal currents over a shallow ocean floor produces turbulence of sufficient intensity to keep the entire water column well mixed throughout most of the year. Nutrients which usually accumulate in the sediment and are no longer available to support marine life, are continuously kept in suspension under such conditions. These coastal seas are therefore among the most productive fishing regions of the world ocean, rivalling the great coastal upwelling regions and the fertile Southern Ocean. The North Sea or the Newfoundland Banks are two examples of regions where tidal mixing keeps nutrient concentrations in the water column at a high level.

Tides in shallow water are generally a mixture of propagating waves and standing waves. One major difference between these two types of waves is the phase relationship between elevation and tidal current. As could be seen from the example of the water bowl or tank, currents and water level are 90° (or a quarter period) out of phase: Currents are strongest when the water surface is flat and vanish when the water level is at its highest and lowest (high and low tide). In propagating waves, on the other hand, currents are strongest at high and low tide, ie they are in phase with the elevation. For a given coastal location the time of strongest tidal current relative to high tide therefore depends on the type of tidal wave in the region.

Sudden changes in water depth can lead to a change of the tide from a standing wave to a propagating wave. This occurs because the propagation speed of shallow water waves depends on the water depth. If such a wave encounters a sudden change of depth, its propagation speed is slower over the shallower region than over the deeper region; its propagation speed on either side of the sudden depth change is mismatched, and the wave cannot continue unchanged across the changing topography. This leads to partial reflection of the wave. If a wave approaches a steep rise of the sea floor (Fig. 5.4), part of the wave continues as a propagating wave in the shallow water, while part of it is reflected back into the deeper water and combines with the incoming wave to form a partially standing wave. Tidal currents and elevation are thus in phase in the shallow part but out of phase, by a degree determined by the wave's reflection coefficient (Fig. 5.4), in the deeper part. This explains the wide range of observed phase relationships between tidal currents and high or low tide in the world ocean's shelf seas.

This looks interesting but sci-hub is blocked for me.
 https://doi.org/10.1029/JC083iC09p04607
Quote
Abstract

A well‐defined class of fronts occurring in the shelf seas around the United Kingdom during the summer months marks the boundary between stratified and vertically mixed regimes. The occurrence of these fronts may be interpreted in terms of the distribution of available turbulent kinetic energy from the tidal currents and wind stress and the buoyancy flux input at the surface. The principal parameter controlling stratification is the ratio of the water depth to a Monin‐Obhukov length determined by the tidal velocity. A corresponding parameter based on the wind stress is also found to contribute significantly in a combined model of tide and wind mixing. Vertical sections perpendicular to the front by undulating CTD indicate a strongly baroclinic region with horizontal temperature gradients of ∼1°C/km, which imply strong flows parallel to the front. Drogue observations show that nontidal velocities of ∼10 cm/s occur in the vicinity of the fronts but the flow regime is apparently complicated by large‐scale (∼25 km) instabilities which are clearly manifest in satellite infrared imagery and airborne radiation thermometer surveys. There is also indirect evidence for vertical motions suggesting that both upwelling and down‐welling occur in the frontal zone.
Title: Re: Tides
Post by: uniquorn on April 02, 2020, 11:08:47 PM
I'd like to refer you to uniqorn's "where does the water come from" comment above. Even the best and most valuable of members, that have been providing the rest of us with a constant and positive input (such as yourself) can be totally off when it comes to such basic scientific facts as what a pressure wave actually is.

That is why I dare! Because none of us knows all, but some of us have a better basic understanding of physics than others. This basic understanding can of course lead you into the briar patch, but when something jars against it, I not only dare to respond, but I do.

So silly claims, such as that the phases of the moon can effect Fram export, will be bashed by me now and in the future.
When the tide goes up, where does the water at the bottom come from?
Same happens when changes in atmospheric pressure cause corresponding changes in sea surface (appr. 1 cm per millibar, see here (https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/96JC02920)). Whithin the Northern Atlantic and the Arctic, differences in atmospheric pressure from one place to another can easily exceed 50 mbar, leading to a difference in sea level of half a metre. Again, this is due to expansion and contraction of the water column.

Please explain how this is relevant.

Quote
Relation between sea level and barometric pressure determined from altimeter data and model simulations
Philippe Gaspar Space Oceanography Division, Collecte Localisation Satellites, Toulouse, France Rui M. Ponte Atmospheric and Environmental Research, Inc., Cambridge, Massachusetts
Abstract.
The relation between sea level and barometric pressure and, specially, the validity of the inverted barometer (IB) approximation is examined over the global oceans, using nearly 2 years of TOPEX-POSEIDON altimeter measurements. Both crossover differences and collinear differences between consecutive cycles are utilized in this study. Linear regressions between barometric pressure and sea level time series yield coefficients between 0.8 and 1 cm/mbar poleward of 20 ø and as low as 0.5 cm/mbar in the equatorial regions. Such deviations from the IB value of 1 cm/mbar can be due to the presence of data errors or to correlations between pressure and adjusted sea level (i.e., sea level corrected for IB effect). A simple error model for the pressure fields and a number of sensitivity tests are used to evaluate the changes in the regression coefficient possibly induced by data errors (pressure errors, altimeter measurements errors, and radial orbit errors). The combined (root-mean-square) effect of the different errors amounts to 0.8 mm/mbar poleward of 20 ø and 1.8 mm/mbar within 20 ø of the equator, in general smaller than the observed deviations from the IB value. Regression coefficients thus imply a correlation between adjusted sea level and pressure. Results from a shallow-water, global ocean model forced by realistic wind and pressure fields corroborate this finding. The model is able to explain the observed coefficients, within measurement errors, with wind- driven effects being most important in accounting for differences from the simple IB model. Pressure-forced dynamical signals cause maximum deviations of only 1 mm/mbar. The analyses point to the general validity of the IB approximation over the deep oceans but also highlight the complex relation between sea level and barometric pressure resulting from correlations between various sea level signals.

This (https://www.researchgate.net/publication/225762062_Atmospheric_forcing_of_Fram_Strait_sea_ice_export_A_closer_look) might have been a better riposte
Title: Re: Tides
Post by: Andreas Muenchow on April 03, 2020, 05:22:39 AM
Tides can be tricky and much confusion exists. There is tidal forcing involving gravity and rotations of planetary objects (earth, sun, moon), there are tidal sea level oscillations, and there are tidal currents. All are related and governed by conservation of mass and momentum.

The tidal motions can always be thought of as waves that propagate around ocean basins in deep water like the Atlantic or Pacific Ocean. The phase speed of the wave is usually sqrt(g*H) where H is the water depth and g=9.8 m/s^2 the constant of gravity, so in the deep ocean (2000 m) the speed is 140 m/s or 510 km per hour which is pretty fast. As this wave propagates into coastal areas the water depth changes and so do wave properties and dynamics. The coastal oceans are forced by the deep water waves as a boundary condition, because the shallow areas have little mass and are not much impacted by the gravitation of the planetary objects. This boundary condition moves water on and off the shallow areas which then respond much like a bath tub response to us trying to make waves with moving water back and forth with our legs. Sometimes resonance results and the wave in shallow are large. This happens in Nares Strait (or the North Sea in Europe), because Kane Basin is somewhat close to a resonating basin whose natural frequency (due to geometry) matches that of the tidal forcing.

Furthermore, the tides in straits or channels such as Nares Strait are forced by the Atlantic tidal wave that propagates both through the Arctic Ocean to force the northern entrance and through Baffin Bay to force the southern entrance. These two "forcing waves" have different amplitudes and phases, so strong oscillating pressure gradients from north-to-south exist that drive tidal currents. If these currents converge, sea level moves up, if currents diverge, sealevel moves down. Think of it like you think of a bathtub where water is added from the faucet and removed by the sink. Sealevel goes up when more water is added than goes out the drain, it goes down when more water leaves via the sink than is added by the faucet.

There is more.

So, does this perhaps answer the question of the original post? 
Title: Re: Tides
Post by: uniquorn on April 03, 2020, 12:04:51 PM
Quote
The coastal oceans are forced by the deep water waves as a boundary condition, because the shallow areas have little mass and are not much impacted by the gravitation of the planetary objects. This boundary condition moves water on and off the shallow areas
Thank you Andreas. The tidal discussion was prompted by comments relating to the Fram Strait but I'm curious whether tidal forces affect sea ice in the area north of FJL and Svalbard where the depth rapidly increases from ~200m to over 3000m into the Nansen basin. I expect that 200m isn't considered shallow, but can your explanation be extrapolated to apply to that depth?
I'm aware that the ice drift is wind driven but the low concentration area doesn't move with the ice.
uni-hamburg amsr2uhh, Svalbard and FJL, mar27-apr2
rammb animation of the same area here (https://forum.arctic-sea-ice.net/index.php/topic,2417.msg246318.html#msg246318)
Title: Re: Tides
Post by: Hopen Times on April 03, 2020, 02:28:25 PM
The ongoing Mosaic expedition would be a prime example - have they ever mentioned tidal effects on the movement of ice around their vessel? Not that I've seen.

MOSAiC writes about tides affecting their floe on 27. March. https://follow.mosaic-expedition.org

Ohboiohboi! All scrambles...

Quote
Even after two weeks, the dynamics of our floe do not calm down. Our ice floe with initially a diameter of several kilometers is getting smaller and smaller as a consequence of natural forces. Tides in the ocean and strong winds in the atmosphere are pushing the floe. At the same time and due to the same forces, the leads around us give space when the ice is relaxing again. These ongoing dynamics keep our personal tensions up: How will the floe look like tomorrow morning? Can we work on the ice? Which installations on the ice might need to be rescued? Can we use the powerline between the ship and the ice floe? Over the last days, the latter was not always the case as the ship was simply moving too much. Also, small "island states" that are not accessible by foot have formed. However, using the helicopters on board, allows to continue our measurements in these outposts with limitations. The expedition name "MOSAiC" says it all!
Title: Re: Tides
Post by: Glen Koehler on April 03, 2020, 04:13:48 PM
  FWIW - It seems that the two sides in this debate are focused on different questions. 
     
     One side documents that tides affect the Arctic Ocean waters, ice, mixing, temperature gradients etc., and thus condition of the ASI. The other is focusing only on Fram Strait export, and saying the because tidal movement alternates, the movement of water south on an outgoing tide is matched by tidal movement north on the incoming tide, so in terms of Fram Export it has zero net effect.

     Maybe it's time for a real expert to address the original question directly:  Do changes in tidal forces across the lunar cycle influence the net amount of ASI export through the Fram Strait? 

     At least I think that is the question.  I don't know enough to have an opinion, just trying to clarify the discussion.  All I do know is that my friend retired from 30+ year career at National Weather Service said that tidal mathematics is really complicated!
Title: Re: Tides
Post by: blumenkraft on April 03, 2020, 04:56:36 PM
This is the original post:

Tides have no effect on Fram export. Tidal effects (other than a smooth up-and-down motion) are strictly limited to the narrow coastal strip, perhaps 10 meters max into open ocean. Swells and surges can happen in enclosed waters, but only on a scale of a few hundreds of meters.

If you think differently, you can start your own thread and explain your reasoning there.

So let's sort it out bit by bit.

Quote
Tides have no effect on Fram export.

Since tidal forces are prevalent in all of the Arctic ocean (or any ocean for that matter), and also at the Fram strait, this is inherently wrong.

For example, we have the Yermak plateau, which causes lateral surface movement when tides come in and out. This is a pretty strong effect sometimes. Ice floes in this area will be smashed into small pieces. Wind can move small ice floes more easily than if it was, say, a homogenous ice surface.

A GIF, making this effect pretty obvious, can be seen here >> https://forum.arctic-sea-ice.net/index.php/topic,2649.msg244558.html#msg244558

Or here >> https://forum.arctic-sea-ice.net/index.php/topic,2649.msg218362.html#msg218362

Binntho commented on that one BTW:

Great work! Some sort of tidal effect seems the best explanation. But the circular movement indicates (to me at least) something rising from below. How can that be caused by tides?

Next,

Quote
Tidal effects (other than a smooth up-and-down motion) are strictly limited to the narrow coastal strip, perhaps 10 meters max into open ocean.

I think he meant to say 10 Km here, not meters? Anyway, as seen in the linked GIF above, which is halfway between Greenland and Svalbard (meaning nowhere near a coastal stip) this statement is obviously wrong.

Quote
Swells and surges can happen in enclosed waters, but only on a scale of a few hundreds of meters.

I mean, what does that even mean?

Quote
If you think differently, you can start your own thread and explain your reasoning there.

We did. A lot of reasoning, proof, and expert knowledge in this thread.



BTW, last year we had a lengthy discussion where Binntho vehemently stated that lateral movement due to tidal waves was not a thing at all. He was (maybe still is) convinced tides can move ice only up and down. No paper, no expert opinion, no illustrative GIF was able to convince him otherwise.

Let's see if he comes around this time.

Experts reading this, please point out if i made any wrong statements above. I, for one, am willing to learn.
Title: Re: Tides
Post by: johnm33 on April 03, 2020, 11:27:49 PM
This is my take on tidal effects on the Arctic, i'm no expert this is just what i think i'm looking at on the various models and images available to us all. I'll start at the ridge between Scotland and Iceland. For about 13hrs. a day tides lift water over the Faroes ridge into the Norwegian/Greenland seas, the sea height rises by 40-60cm depending on the tidal cycle, so I'm guessing that at the lower end that amounts to a volume of about 20cm over the whole area and nearer 30cm at peaks and this volume delivered twice[almost] a day. Once the tidal forcing stops the residual current continues, this makes it difficult for the same body of water to recycle south. In fact this water coming from the south has inherent energy/inertia exceeding the Earths surface rotational speed here and it is thus pressed against the west coast of Norway, so a different source is needed for the water flowing south, this comes from both energetically depleted water that has circled N/G seas and from an induced flow out through Fram. The inducement is the steady flow through Denmark strait where the biggest waterfall in the world drops basal waters into the N. Atlantic.
From 60oN the northbound flows own movement adds to it's relative inertia, since from here it more or less approaches the axis of rotation directly and the planets tangential surface speed diminishes rapidly. This gives it the momentum to scale the Barentz shelf or to penetrate Fram and deliver Atlantic water as deep into the Arctic as energy permits. Since the loss of sea ice in Barentz, which acted like a baffle in a silencer, or leaves on traffic noise, and caused a chaos of churning which inhibited flow, the tidal surge penetrates further, followed at a more sedate pace by actual A.W. which melts more ice rinse repeat. Then on the coat tails of the tidal surge slowly a residual current builds and becomes established. Note that the tidal surge is going the 'wrong' way due to it's inherent inertia so at some point as Chukchi/ESS and Laptev shed ice there'll be a counter surge building up on the Pacific side which cause a turbulent halt, some melt, then at equilibrium these waters will move gently towards the pole/Fram, as they are replaced.
For me the 'tidal' movement of the ice is a consequence of this penetration which in turn depends on both tidal cycle forcings and atmospheric pressure in that if the mslp is low in both the Norwegian sea and Barentz south of Svalbard then the effect is maximised but even then depends on pressures over the basins. Clearly the more water that enters from these forcings the more has to flow out through Fram, and to a lesser degree Nares, both of which act in some way as flywheels in the system, evening out flows, naturally as the 'flywheels' speed up they will create deficits enhancing inflows from both the Atlantic and Pacific sides.
(https://ars.els-cdn.com/content/image/1-s2.0-S0078323415000883-gr2.jpg)
There's an illustration of tidal forcings on page 12 of this, https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2008JC004941
This animation suggests a rotating wave around the amphidromic point south of Greenland, i'm thinking that beyond and past Iceland different bodies of water are on the move.
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fwww.freegrab.net%2FTide%2520waves.gif&hash=47ddd767d2ff2d19d6dd594d6cf3e1e9)
Title: Re: Tides
Post by: kassy on April 04, 2020, 01:28:34 AM
That is some cool stuff, always more to look into.

Lets note that there are 2 things.

The narrow claim form post 11:
That changes in Fram export that we have seen over the last months are somehow linked to phases of the moon. (And its effects on tides, K)


And 2 basically how it all works for us less versed in this stuff and interested in finding out more.

I wonder if anyone with more knowledge of the physics could chime in on 1.

Everything more on 2 is great too.
Title: Re: Tides
Post by: binntho on April 04, 2020, 07:35:24 AM
I must begin my post by apologizing for my silence - I am currently isolated in a three-house compound within spitting distance of the source of the Blue Nile, along with 3 "adopted" young men. Internet connectivity here is limited and fluctuating (albeit not with the phases of the moon as far as I can see). My work is heavily dependent on Internet access so most of the available bits have to be utilized for work rather than play.

On other personal notes (since somebody saw reason to wonder), I am an Icelandic national and well acquinted with tidal forces in coastal areas around Iceland that see some of the biggests tidal fluctuations in the world (although nowhere near as impressive as on the Canadan Pacific coast, or so I hear). My experience does include being severely seasick in small vessels during storms,  but the shipboard episodes of my life are thankfully few and far between.

Having lived on the east coast of Sicily for many years has also acquainted me with the strong coastal current that arises every now and then and some say are linked to the tides. But tidal movement in the Mediterranean are mostly very small and complicated, with the Messina current being well established as a tidal current, resulting from the (small but still existant) out-of-phase tidal movements oft he Ionic and the Tyrrhenian seas.
Title: Re: Tides
Post by: binntho on April 04, 2020, 07:54:08 AM
uniqorn - my apologies if I have misconstrued your comments. I have read your posts, and commented on some of them for some time, and you have on occasion commented on mine. But your contributions to this forum outweigh mine by a long shot, it is I who benefit from reading your posts and most likely not the other way around!

Seeing as how you have dregged up some of my earlier contributions, I would like to clarify:

I have "always" (let's say, for the last few decades), been of the opinion that tidal movement is primarily an up-and-down movement caused by changes in gravity.

Ghanges in gravity cause changes in pressure, which causes the water column to expand and contract. Changes in atmospheric pressure also cause changes in pressure within the water column, causing the water column to expand and contract. Hence the two phenomena are linked, and they are also of a similar magnitude.

If we were to put a number on the magnitude of the tidal force on the oceans of the world, then by far the largest number would be put on vertical movement in deep, open water. This does not exclude lateral movement in shallow coastal areas.

Tidal currents in the North Sea, tidal swirls over shallows and in and out of fjords along the Greenland coast, all of these are real and natural and should not surprise anybody. The existence of these does NOT imply that similar forces are at play in the open oceans.

And this is where I think that most of the current misunderstanding of tidal movement stems from: Very many people are aware of, and even have direct experience of, strong tidal movements close to shore. They extrapolate this and think that the 450 km wide Fram strait must have similar tidal currents. Well it doesn't.
Title: Re: Tides
Post by: binntho on April 04, 2020, 08:15:47 AM
Most ocean waves are not pressure waves. Tsunamies are the only large-scale example I can think of.  The tidal "wave" is therefore definitely not a pressure wave as such.

The two daily waves that seem to propagate from west to east every day are caused by the tidal effect being (relatively) static while the Earth rotates underneath (picture 1)

Density of water changes with pressure (see picture 2), and even if the effect is small, the oceans are very deep. So the biggest effect happens over the deep oceans.

But where is the biggest tidal effect felt? This is much more complicated. There is an west-to-east component and even a slight south-to-north (e.g. around Iceland, the tide hits the south-west first, and the north-east last). But the shapes of the oceans, their bathymetry, and the relentlessness of the tidal cycle, results in the tidal effect being very strangely distributed (see picture 3)
Title: Re: Tides
Post by: blumenkraft on April 04, 2020, 08:21:10 AM
Quote
Let's see if he comes around this time.

Nope. Just keeps spamming.
Title: Re: Tides
Post by: binntho on April 04, 2020, 08:24:40 AM
In the prevous post, the tidal component in the Arctic could not really be seen. But a very quick Internet search found the following, which I must say surprised me very much.

There hardly seem to be any tides in the Arctic at all! So I think we can lay to rest once and for all any discussion of whether and how the tides can affect sea ice in the Arctic ocean.

The image is from here (https://www.esa.int/ESA_Multimedia/Images/2019/07/Amplitude_of_the_main_tidal_component_in_the_Arctic_Ocean).
Title: Re: Tides
Post by: binntho on April 04, 2020, 08:25:44 AM
Quote
Let's see if he comes around this time.

Nope. Just keeps spamming.

I'm saddened, blumenkraft. I truly expected better of you. Do you think that honest disagreement, dissemination of information and willingness to debate are "spamming"?
Title: Re: Tides
Post by: binntho on April 04, 2020, 09:00:37 AM
This whole tidal debate has in my mind always been about coastal vs. total.

The total effect of tides on water movement are totally different from localized, and coastal, effects. Lateral movement is obvious in the latter, negligible in the former.

The most recent example of lack of understanding of how tides work was the claim that the phases of the moon could somehow visibly affect Fram export.

The one before that was when someone talked about a "tidal surge" entering the Arctic Ocean.

What perhaps surprises me most is not that a few simple souls can make such claims, but that the rest of this forum does not understand why those claims are so wrong.

And unfortunately, blumenkraft and other very valuable members of this forum continue to refuse to understand why silly claims about the tides simply cannot be right. There is no tidal surge in the Arctic ocean (nor can there be), and the phases of the moon do not visibly affect Fram export.
Title: Re: Tides
Post by: P-maker on April 04, 2020, 09:03:56 AM
Binntho, nice to know that you are safely up into the mountains in Africaåq and away from the frigid ocean. Also, nice to know of your Icelandic origin, which bothers for an illiterate mind and a couragious world-view.

If you take a closer look at the tidal map you presented, you will see that the Fram Strait is exactly the place, where a tidal "front" exists. North of it, there is hardly any tidal waves. South of the line between NE  Greenland and Svalbard the tidal amplitude suddenly rises to 0.5 m.

Please reconsider, whether such a twice-daily "pull" of low water tide in the Greenland Sea would have have any noticable effect on the export of polar sea ice.
Title: Re: Tides
Post by: binntho on April 04, 2020, 09:12:56 AM
Please reconsider, whether such a twice-daily "pull" of low water tide in the Greenland Sea would have have any noticable effect on the export of polar sea ice.

What "pull" do you mean. What is pulling on what, and how?

And if a twice-daily "pull" then there must be an equal and opposite twice daily "push"? Leaving us with no net effect at all.
Title: Re: Tides
Post by: binntho on April 04, 2020, 09:16:10 AM
Binntho, nice to know that you are safely up into the mountains in Africaåq and away from the frigid ocean.

Thanks. It's a little bit strange thinking of this as being "up in the mountains" since I'm sitting next to a huge lake in an extensive flatland surrounded by mountains. But on the other hand, I am at an altitude of almost 2000 meters.

The nearest ocean is not "frigid", in fact, you would have difficulty swimming in the 40+C surface waters due to heat. And in Iceland, we don't usually consider the ocean "frigid" since it is more often than not warmer than the air!
Title: Re: Tides
Post by: P-maker on April 04, 2020, 09:30:04 AM
Binntho,

If your DTU Space-derived map is nearly correct, the sea level in the Greenland Sea will be half a meter lower twice a day than sea level North of the 80 degrees parallel in the Fram Strait.

This means that there is an immediate "pull" southwards twice a day, which may contribute to the "fracking" or "cracking" seen these days north of 80N.

It is the "pull" that does it, not the "push" at high tide in the Greenland Sea.
Title: Re: Tides
Post by: binntho on April 04, 2020, 10:14:09 AM
If your DTU Space-derived map is nearly correct, the sea level in the Greenland Sea will be half a meter lower twice a day than sea level North of the 80 degrees parallel in the Fram Strait.

This means that there is an immediate "pull" southwards twice a day, which may contribute to the "fracking" or "cracking" seen these days north of 80N.

It is the "pull" that does it, not the "push" at high tide in the Greenland Sea.

You imagine that because the surface is lower in one place than it is in another, then there should be a gravity-induced pull from one to the other. This is intuitive, but wrong when it comes to tides.

Just to be clear: We are talking about deep ocean, hundreds of km from the nearest shore. So there is no coastal effect.

The tides move up and down due to changes in gravity. So the surface is always at the same "level" of gravity, whether it is one meter higher or lower.

For there to be a gravitational pull (e.g.. down a slope) there has to be a difference in the gravitational pull at the surface at the top of the slope and at the bottom - there has to be a difference in what is often termed "potential energy" of any object on the upper and the lower parts of the slope. But since the graviational pull at the surface is the same (because the surface responds to changes in gravity by going up and down), no potential energy difference exists.

There is therefore no "pull" from the tide-lowered South Greenland sea, just as there is no "push" from the tide-raised South-Greenland sea, when compared to the Fram Strait boundary.
Title: Re: Tides
Post by: oren on April 04, 2020, 11:16:33 AM
Binntho you keep ignoring the huge difference in depths between bodies of water, even away from your beloved coast . You keep repeating the mantra of the "deep ocean", well if all the oceans were uniform some of the effects being thrown around here would not exist. And yet you ignore this and therefore keep being surprised that people claim there is an effect.
Until you acknowledge this no progress will be made.
To all other posters, well done on digging up so much useful information. Once a separate thread is created this can be done at leisure without disrupting the original thread.
Title: Re: Tides
Post by: binntho on April 04, 2020, 11:48:09 AM
Binntho you keep ignoring the huge difference in depths between bodies of water, even away from your beloved coast

I don't think I do. There is a difference between continental shelves and the deep ocean, of course there is. But the tidal effect is almost all to be found in the deep ocean - both when it comes to area and when it comes to volume and when it comes to sheer energy.

Besides, with the tidal effect being cyclical, expecting any effect to be more than an up-and-down and back-and-forth movement, and therefore essentially zero over any given day  would require a lot of explaining. The tides do cause currents in certain coastal areas, and these currents are able to move ice in one direction in the morning and the other direction in the evening. So what? This is such a collection of basic facts that they should hardly need to be mentioned.

Quote
. You keep repeating the mantra of the "deep ocean", well if all the oceans were uniform some of the effects being thrown around here would not exist. And yet you ignore this and therefore keep being surprised that people claim there is an effect.

I'm not surprised when people claim real effects, effects that all can see and many of us (me included) have experienced directly.

What surprises me is that most of the members of this forum are unable to see that wild claims about "tidal surges" in the deep Arctic, and that Fram export can be linked to the phases of the moon, are so very very wrong.

Quote
Until you acknowledge this no progress will be made.

But I do acknowlege it! I acknowledge all knowledge. I acknowledge all facts. I do not acknowledge wild theories without basis in reality.

The various scientific papers, I acknowledge them all. The gifs that blumenkraft and others have shonw me I acknowledge them all. I have never claimed otherwise.

But I will never acknowledge wild theorizing without any basis in reality. And I am not at all happy with the seeming lack of understanding of basic physics amongst the majority of posters in this forum.

Otherwise, my refusal to admit a moon-phase effect on Fram export would never have lead to this discussion!
Title: Re: Tides
Post by: Hopen Times on April 04, 2020, 01:44:17 PM
binntho, what are your thoughts on MOSAiC´s experiences with the tide? As mentioned in post #24.
 
Title: Re: Tides
Post by: johnm33 on April 04, 2020, 04:01:35 PM
Interesting post here suggesting tidal forces may lift water over the mid atlantic ridge, https://forum.arctic-sea-ice.net/index.php/topic,2022.msg123120.html#msg123120
and another here which may explain some of the 'pull' mentioned above[the vid]. https://forum.arctic-sea-ice.net/index.php/topic,1755.msg199444.html#msg199444
Title: Re: Tides
Post by: oren on April 04, 2020, 06:03:44 PM
Quote
Besides, with the tidal effect being cyclical, expecting any effect to be more than an up-and-down and back-and-forth movement, and therefore essentially zero over any given day  would require a lot of explaining.
Ratcheting. Not such a long explanation I think, a cyclical motion converted to movement by way of something preventing some or all of the return movement. Not happening in the ideal uniform deep ocean but happening in areas with sharp differences in depth, especially where shallower sills, or underwater waterfalls, are involved.
Title: Re: Tides
Post by: Glen Koehler on April 04, 2020, 07:20:36 PM
     If the question is "Does Fram export vary with tidal forces", then getting the daily values used to create the Wipneus Fram export chart and checking for correlation with the lunar cycle would provide evidence to address the question.
https://forum.arctic-sea-ice.net/index.php/topic,119.msg258236.html#msg258236 (https://forum.arctic-sea-ice.net/index.php/topic,119.msg258236.html#msg258236)
Title: Re: Tides
Post by: HapHazard on April 04, 2020, 09:19:51 PM
One person here reminded me of the backfire effect.

The Misconception: When your beliefs are challenged with facts, you alter your opinions and incorporate the new information into your thinking.

The Truth: When your deepest convictions are challenged by contradictory evidence, your beliefs get stronger.
Title: Re: Tides
Post by: tybeedave on April 06, 2020, 12:39:51 AM
good afternoon,

Among the many forces at play in the Arctic, the gravitational flattening of the CAB and its recurving twice/day imparts oodles of energy, (scientists measure it in zillions of joules) every day, sun or no sun, wind or no.  Tides impart a significant amount of heat to and have a significant effect on, the system, even though reduced, at the pole proper.  To ignore this is folly.

It is not also obvious to those whose sunglasses block more than the glare.

I might add that by simple geometry, one can illustrate how a higher tide allows more volume to pass through the Fram.  Though true that generally tide has a to and fro character, that is not currently true in the Fram and into the Greenland Sea. The wind has blown strongly for the last 45 frigging (excuse my english) days in a southeastern direction!!!

The transport has been incredible, and yes, learned friends, high tide, twice a day, every damn day is indeed a real factor, and whether one is blinded or not to reality, waves of ice in a tide-exacerbated flow of an extreme amount, may have mortally wounded the CAB.

That this event has not appeared very robustly in extent and volume stats is interesting.   There is a simple explanation for why observation doesn't agree with measurements.  The older ice floes are separating and a thin layer of new ice forms.  The air is still cold now, but it only freezes a thin layer in all of the newly created areas still categorized as ice.  Created extent evens out the extent stats with mostly newly formed, thin ice, replacing older, thicker floes in droves.

I have no direct reason to explain the stable volume figures other than the time frames disguise it or lack of data.  I just don't know why such a large melt doesn't show up better.  Maybe it didn't happen and I'm the boy crying wolf, but I see the blood of the CAB in this area, and I don't think it's an illusion.

But, I would estimate that possibly 10 % of the CAB has been converted from the solid to the liquid via export through the Fram into the Greenland Sea and into the Barents Sea during this 45-day event.

Hopefully, weather patterns will change soon.  If they don't, and accelerated export continues through the summer (unlikely), the pole may be in open water at some point this year.


The pettiness of ignorance may be cured by the recognition that an important event is going on now and the learning that the more one learns, the more one becomes sure they don't know near as much as they think they do.

Tides are important, imho.

The tide and wind having a coordinated seiche effect on an enclosed basin (CAB) could also qualify as a heat generator as well. Once again, measured in zillions of joules lol

peace

td
Title: Re: Tides
Post by: uniquorn on April 06, 2020, 11:48:30 AM
<>Ghanges in gravity cause changes in pressure, which causes the water column to expand and contract. Changes in atmospheric pressure also cause changes in pressure within the water column, causing the water column to expand and contract. Hence the two phenomena are linked, and they are also of a similar magnitude.<>
A bold claim which should be easy to verify with a volume vs time chart or a scientific paper. A quick search didn't find one. Nevertheless, that search did lead me to the video attached, which is similarly challenging. Thank you.

https://www.youtube.com/watch?v=pwChk4S99i4

Quote
Although each drop of water on Earth is indeed pulled by the moon's gravity, the effect isn't noticeable on a molecular level since the Earth's inward pull is overpowering.

The key, however, is that ocean water covers about 71% of Earth's surface and is connected as one liquid body. This allows the small force on each water molecule to collectively add up to "a pretty decent increase in water pressure," Perez-Giz says.

Molecules of water near Earth's poles are pulled mostly straight down toward the planet's center of gravity (near its core), and the molecules closest to the moon (at Earth's equator) experience the strongest pull toward the moon. Water molecules that are farthest from the moon, meanwhile, feel the weakest gravitational acceleration.

Since water molecules can easily move and bump into one another, these countless tiny nudges add up and "squeeze" seawater away from the poles. This global water pressure works against Earth's gravity to form two bulges: the high tides.

"The ocean isn't being lifted or stretched," Perez-Giz says. "The ocean is bulging along the Earth-moon line in the same way that a blister or pimple will bulge up if you start to squeeze it from the side."
https://www.nsf.gov/od/oia/activities/aaasfellows/bios/perez-giz.pdf
Title: Re: Tides
Post by: tybeedave on April 07, 2020, 04:39:10 AM
 hi yall,

I'm not going to cite anything, but the idea of any liquid pulling anything in any way, shape, or form is misleading.  the only forces of nature that i'm aware of only push. point in case, using a straw to drink with.  one doesn't actually suck the drink up against gravity, one lowers the pressure and atmospheric pressure pushes it up thru the straw to your mouth.

the same forces are at work in Fram export.  Higher pressure from physical forces caused and transferred by collisions between floes does create pressure in a particular direction, add to this tide and local wind and there is a perfect storm for export.    a significant amount, imho, of the CAB just got spit out via the Fram and to a lesser, but not insignificant, volume of older ice into the Barents Sea.

Until one recognizes the actual causality to an event, understanding is unlikely

Sometimes events are hidden because of the fear of being the one called out with chants of "prove it"

Sometimes events aren't recognized because of the chatter drowns out the data. 

Sometimes one can be wrong, but i fail to see such incorrect examples except in my bell-ringing, uncited, wake-up approach and what i feel is a more detrimental approach as that displayed by binntho which celebrates misdirection and denial.

peace and excuse the lack of capitalization, but today, the 7th, is my birthday and i've been celebrating all day.  don't worry, i quit drinking a long time back when i began to have children.  so, what i type is thought out, even if possibly incorrect.  in other words, for at least the next 24 hrs, i will listen to anyone but care less :P

td
Title: Re: Tides
Post by: Hopen Times on April 07, 2020, 09:07:08 AM
I am trying to understand how tides are supposed to give changes in how much ice that moves thru Fram Strait over time, but it is hard for me to understand it. I have no problem seeing that the tides moves the ice back and forth, but in my head the back and forth movement ends in zero movement caused by the tide. How can it be anything else than a back and forth movement ending in zero movement?

Here is video I made, showing how tides move ice back and forth. Sorry for the repost of it, but I think it gives a nice example of how the tides moves ice back and forth. It is made here: https://norgeskart.no/#!?project=norgeskart&layers=1011&zoom=7&lat=8519505.88&lon=777966.88
There is a current moving south in this area.
In the clip starting at 2:18 the wind is acting as well.
I know this is not the Fram Strait.

https://www.youtube.com/watch?v=YBTVJIH6En8

Title: Re: Tides
Post by: oren on April 07, 2020, 09:22:49 AM
HT, it depends on  the location but it's not necessarily a net zero. Suppose the tide pushes the ice beyond a headland where the currents are different and they carry the ice away. Some kind of ratcheting is possible, depending on the geometry and the bathymetry.
Title: Re: Tides
Post by: Hopen Times on April 07, 2020, 10:24:40 AM
Thanks oren. I think I can see that. Then I wonder, is the geometry and bathymetry in the Fram Strait like this? Further, can it have any big effect on the export numbers in the Fram Strait? Asked in a silly way, can we say, here comes a big tidal wave an it is going to move a lot more ice than normal thru the Fram Strait?
Title: Re: Tides
Post by: johnm33 on April 07, 2020, 10:45:05 AM
"If the question is" My suggestion is that tidal forces, which have always operated, are now pushing more A.W. deeper into the Arctic via the Barentz shelf and these surges/pulses are beginning to become detectable. The surges create turbulence and I'm guessing some internal waves as they reach the basins, they force temporary currents some of which persist a while and may become permanent. These temporary currents themselves ease the influx of more A.W. and since the Arctic sea level remains self similar there has to be an increased outflow and it seems to me that this is below the shear level of the water held steady by the chaotic underside of the ice. The surges happen at speed the actual water trails far behind probably best judged by late +temp. anomolies in Kara/Laptev.
The full moon is upon us, and the biggest tides of the year so either the flow will be contained in the Norwegian/Greenland seas and thus halt the outflow or it will penetrate into Barents accelerating outflow. A possible proxy is the anomoly by Svalbard, here the flow of A.W. has moved directly north gaining about 16mph pero relative to its position and moving towards the rotational axis has also gained/lost[?] +/-angular momentum such that if it builds up both forms of kinetic energy will be expressed there as heat, both here and Barentz by the white sea anomolies are rising at the moment. Todays mslp suggests more contained tomorrows suggests not.
Title: Re: Tides
Post by: oren on April 07, 2020, 10:49:20 AM
To be honest, I think the effect of tides is cumulative and not necessarily driven by a specific tide. But perhaps a period of higher tides (king tides, spring tides) could have some non-negligible effect, as sometimes happens with iceberg calving.
I don't pretend to know if the effect is strong or very weak, but I am sure it is not zero, which for me was the original debate about tides and ice.
Title: Re: Tides
Post by: Andreas Muenchow on April 08, 2020, 01:39:30 AM
Tidal currents in the Arctic Ocean are small (< 5 cm/s) and this applies to Fram Strait as well. Furthermore, these tidal currents are largely linear which means that the water going into the Arctic during the "flood" is the same that comes out of the Arctic on the ebb. For linear wave motions the average velocity over a wave period is zero. Sinusoidal (linear) waves do not transport mass or matter such as ice or water, they transport energy. (A tsunami is a very good analogy for this.)

Only if the wave amplitude is similar to the water depth does a wave transport matter and energy. This (nonlinear) process closely relates to wave breaking.

Tides have a negligible effect on the flux of sea ice into or out of Fram Strait.

P.S.: Tidal currents are strong in Nares Strait (~ 1 m/s), but as in Fram Strait the tidal currents move ice back and forth only with a net displacement (during an entire tidal cycle for the tidal current) is close to zero.
Title: Re: Tides
Post by: Jim Hunt on April 08, 2020, 03:01:24 PM
See also this from Copernicus:

https://twitter.com/CMEMS_EU/status/1247808183436894215

Quote
New Arctic Ocean tidal current forecast model is now available using a high-res. numerical model. Such tidal current information is used across a wide range of applications including: coastal management, marine renewable energy, navigation & more!
Title: Re: Tides
Post by: tybeedave on April 08, 2020, 11:48:49 PM
It pains me when one can't see the forest for the trees.

Nowhere did anyone say that tides were the driving force behind Fram export.  The wind is the driving force, and while the synergetic addition of the tide is a relatively minor, yet significant contributor to export volume, the tide goes up and down, except when windblown. then things go sideways in more than one respect.

I thought this wind event was subsiding, but it continues melting much older ice than the 'normal' sloshing in Fram.  Tide or no tide, it is a major event, imho.

Lets stop arguing about trivial differences in definition.  as richard feynman said, ' you can know the all the names of all the birds, but that doesn't help you understand birds.

td
Title: Re: Tides
Post by: uniquorn on April 10, 2020, 05:07:21 PM
Internal Waves and Mixing in the Marginal Ice Zone near the Yermak Plateau
https://journals.ametsoc.org/doi/full/10.1175/2010JPO4371.1
Quote
The aim of this study is to investigate the role of tides, internal waves and topography in mixing near the Yermak Plateau. To this extent, we use day-long time series of finescale and microstructure measurements at stations near the ice edge over the southern YP. The present work has implications beyond the study site, for the Arctic Ocean in general. Although peripheral regions such as the YP are home to anomalously large tidal velocities (30–40 cm s−1; Padman et al. 1992; Padman and Erofeeva 2004), the maximum tidal velocities over most of the central Arctic Ocean are sufficient (5–10 cm s−1; Kowalik and Proshutinsky 1993) to generate internal waves over suitable topography such as midbasin ridges and the continental shelf break. Including a simple representation of tidal mixing in a coupled ocean–ice model for the Arctic Ocean, Holloway and Proshutinsky (2007) show that tides enhance loss of heat from AW and have profound implications for Arctic hydrography and circulation. Furthermore, studies in the marginal ice zone (MIZ) can aid understanding how the decreasing trend in Arctic ice cover (Giles et al. 2008) will affect the vertical mixing. Currently, the deep Arctic Ocean away from coasts and submarine topographic features is a remarkably quiescent environment (Rainville and Winsor 2008; Fer 2009). Maintenance of this weak turbulent mixing in the interior Arctic Ocean is crucial for the cold halocline layer (Fer 2009), hence the ice cover, and the AW layer circulation (Zhang and Steele 2007). However, recent finding shows that large inertial waves, enhanced shear, and mixing are tightly related to the absence of sea ice (Rainville and Woodgate 2009). In a seasonally ice-free Arctic, vertical mixing can be comparable to the levels in the MIZ with potential impacts on the heat content in the upper-layer circulation, nutrients, and the ecosystem.
Title: Re: Tides
Post by: johnm33 on April 10, 2020, 10:12:51 PM
Whilst i'm not suggesting that the tidal forcings are localised to Fram [more Barents and deeper penetration] there are tidal forces local to Fram. The tidal 'pressure' builds for about 6hrs. and since the water arriving has some additional inertia once through Fram much of it moves too far away to be drawn back as the pressure reverses. Also the A.W. is more saline/denser and moves through at a deep level, some fraction of it is drawn towards Nares by tidal forces there and has formed a permanent deep southbound current, another fraction is drawn along the face of the shelf north of Barentz, this too has become an established current. So even here as water flows in at depth a separate higher layer of water moves out in it's stead.
" Abstract

An upward‐looking Acoustic Doppler Current Profiler deployed from July 2007 to September 2008 in the Yermak Pass, north of Svalbard, gathered velocity data from 570 m up to 90 m at a location covered by sea ice 10 months out of 12. Barotropic diurnal and semidiurnal tides are the dominant signals in the velocity (more than 70% of the velocity variance). In winter, baroclinic eddies at periods between 5 and 15 days and pulses of 1–2 month periodicity are observed in the Atlantic Water layer and are associated with a shoaling of the pycnocline. Mercator‐Ocean global operational model with daily and 1/12° spatial resolution is shown to have skills in representing low‐frequency velocity variations (>1 month) in the West Spitsbergen Current and in the Yermak Pass. Model outputs suggest that the Yermak Pass Branch has had a robust winter pattern over the last 10 years, carrying on average 31% of the Atlantic Water volume transport of the West Spitsbergen Current (36% in autumn/winter). However, those figures have to be considered with caution as the model neither simulates tides nor fully resolves eddies and ignores residual mean currents that could be significant.
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017JC013271
Title: Re: Tides
Post by: uniquorn on April 11, 2020, 02:06:03 PM
Here showing an animation of 3 mosaic Pbuoys  (https://data.meereisportal.de/gallery/index_new.php?active-tab1=method&buoytype=PB&region=all&buoystate=active&expedition=MOSAiC&buoynode=all&submit3=display&lang=en_US&active-tab2=buoy)that report location and drift speed every 30mins. It runs at 24 frames/sec so 12hrs/sec. I think I can see lurches in speed roughly every second so I subtracted the drift speed from 6hrs before in each row to show the difference.

6hr difference = driftspeed(t)-driftspeed(t-6hr)

P201 is the top one. Is the method meaningful?
edit:I made a mistake and the p201 chart is for 5hr difference. I looked at P204 and calculated 4 to 6.5hr differences to see what they look like. The curve shifts along the time axis as anticipated but drift speed difference was more variable than I expected over time. (Converted to km/hr.)
click for full resolution.
Some clean peaks and troughs for calculating frequency.
Title: Re: Tides
Post by: johnm33 on April 12, 2020, 01:14:12 AM
'meaningful' not yet but there are some indications, for instance the mslp and full moon tides [which i see as a seven day event balanced around the actual] seemed to indicate a slowdown before the 8th and then an acceleration of forcing by both diversion of A.W. onto Barentz shelf and consequentially more  'suction' by low tides  seems to be present [though there may be other explanations]. So another tool[complication] in the box. Thanks. When the actual 'surge' from deeper penetration of A.W. comes remains to be seen, IF. But this is best guess territory and the more tools the better.

Title: Re: Tides
Post by: uniquorn on April 20, 2020, 12:54:46 AM
Following up on using buoy data to show tidal movement, here are a selection of Mosaic Pbuoys that calculate drift speed every 30minutes. The 6hr difference in drift speed is shown by colour and size.
Just over 17 days in 815 frames, 24 frames/day running at 12 frames/sec
edit: reposting with negative drift speed
No graticule as processing takes too long
Title: Re: Tides
Post by: johnm33 on April 20, 2020, 10:36:27 AM
This (https://thebarentsobserver.com/en/node/4811) doesn't specifically refer to tides but it's implicit that if the Atlantic front can move with the seasons then it can also move with the tides. Thus on the surface at least it's probable that the same water moves into and out of the Arctic as the tidal pressure waxes and wanes. Not sure the buoys are close enough to feel this yet but another signal to look for.
 Evidence for where any Atlantic waters entered in the last tidal cycle are ambiguous at best but glbhycomsss (https://media.giphy.com/media/KchXoULjX8UdPSdf8g/giphy.gif) shows increase both towards Banks is. and above Lomonosov opposite St. Anna with subtle changes to Laptev.
Title: Re: Tides
Post by: uniquorn on April 20, 2020, 11:19:33 AM
I struggle to reconcile the connection between ocean currents (and possibly tides) with the Lomonosov ridge because the peaks are ~1500m deep but the Mercator model (https://forum.arctic-sea-ice.net/index.php/topic,2417.msg245537.html#msg245537) implies a connection.

A max drift speed difference of ~0.5km/hr in deep waters is not much and the movement is likely to be 'smoother' than a wind shear, for example. However, the effects may be becoming more apparent as the ASI thickness decreases.

I took a closer look at P157 in the Laptev last october.
Title: Re: Tides
Post by: johnm33 on April 20, 2020, 02:51:22 PM
St. Anna bottoms out close to 700m so in your graphic within the Atlantic Water layer, i'm thinking that the largest fraction of tidal driven A.W. leaves Barentz here. Dropping into the basin it causes waves in the Arctic Deep Water layer which radiate out, as ripples in a pond except for the complications of being at the interface of two dense mediums, so these internal waves travel directly towards Lomonosov but also reflections of them arrive in interference patterns [that remain opaque] and it's the turbulence generated as these pass the ridge that causes vertical mixing. The actual water probably turns right[east] and adds to the complex of waves traversing the deep layer, it may even be that it's energy is showing up in ESS causing the movment there apparent in Aluminiums gif.  [I think]
 The gifs motion does tie in with the number of tides.
Title: Re: Tides
Post by: uniquorn on April 20, 2020, 05:25:18 PM
Mercator (model) salinity at 300m shows turbulence beyond the Nansen/Gakkel ridge but not much. A daily image wouldn't show tides and I doubt that it models internal waves but took a look anyway. Ani runs at 61fps (~6sec/year).
gmrt bathy (https://www.gmrt.org/GMRTMapTool/np/) for reference.

https://polarresearch.net/index.php/polar/article/download/3094/html?inline=1
Quote
Abstract

The Barents Sea throughflow accounts for approximately half of the Atlantic Water advection to the Arctic Ocean, while the other half flows through Fram Strait. Within the Barents Sea, the Atlantic Water undergoes considerable modifications before entering the Arctic Ocean through the St. Anna Trough. While the inflow area in the south-western Barents Sea is regularly monitored, oceanographic data from the outflow area to the north-east are very scarce. Here, we use conductivity, temperature and depth data from August/September 2008 to describe in detail the water masses present in the downstream area of the Barents Sea, their spatial distribution and transformations. Both Cold Deep Water, formed locally through winter convection and ice-freezing processes, and Atlantic Water, modified mainly through atmospheric cooling, contribute directly to the Barents Sea Branch Water. As a consequence, it consists of a dense core characterized by a temperature and salinity maximum associated with the Atlantic Water, in addition to the colder, less saline and less dense core commonly referred to as the Barents Sea Branch Water core. The denser core likely constitutes a substantial part of the total flow, and it is more saline and considerably denser than the Fram Strait branch as observed within the St. Anna Trough. Despite the recent warming of the Barents Sea, the Barents Sea Branch Water is denser than observed in the 1990s, and the bottom water observed in the St. Anna Trough matches the potential density at 2000 m depth in the Arctic Ocean.
Correspondence
Vidar S. Lien, Department of Oceanography, Institute of Marine Research, P.O. Box 1870, NO-5817 Bergen, Norway. E-mail: vidar.lien@imr.no
(Published: 20 September 2013)

If this is too far off topic I'll move it to the AO salinity thread
Title: Re: Tides
Post by: oren on April 20, 2020, 05:42:03 PM
Good post which contributes to the discussion at hand. I suggest to cross post it to the other thread as well, as it contains useful stuff.
Title: Re: Tides
Post by: johnm33 on May 01, 2020, 11:28:18 AM
A cut and slowed version of the current Hycom animation 0804-0705
(https://media.giphy.com/media/SRMOrfDLozHCa5nZFk/giphy.gif)
I'm thinking the openings in the upper left quarter are caused by internal waves generated by tidally driven waters falling into Nansen from St. Anna. Some hint of them are present on the salinity gif (https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/arcticsss_nowcast_anim30d.gif) but anything i try to enhance it destroys detail so best looked at as is, looking [zoomed in] at the 150E-pole line, and whilst it's open noting the increasing salinity across the CAAs Arctic coastline.
+
Plus a close up from 28:04
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpuu.sh%2FFERHS%2F4a50623253.jpg&hash=bd6cc1e3ce449dea9d1f456d69af032a)
Title: Re: Tides
Post by: uniquorn on May 27, 2020, 12:02:58 AM
https://follow.mosaic-expedition.org/ mentions tides again today with no accompanying data or detail. Mosaic buoy P128 is, I think, the southernmost Pbuoy yesterday at
2020-05-25T22:00:00   81.2715   7.8702
further south than Polarstern according to Fomo.

The 6hr drift speed doesn't show a large increase in tidal drift since April1. Maybe the effects are more noticeable when attempting ice-breaking.
Title: Re: Tides
Post by: johnm33 on May 28, 2020, 12:07:42 AM
Figured out how to expand the hycomsss without ruining all detail. This could go in 'waves' too but I'm looking at the tidal 'effects' here the interference waves generated by deep water movements washing up against Lomonosov [imho]
(https://media.giphy.com/media/Ssa9sn21GKha8F8PNz/giphy.gif)
 short read for anyone interested https://syrte.obspm.fr/jsr/journees2014/pdf/Sidorenkov.pdf
Title: Re: Tides
Post by: johnm33 on June 02, 2020, 09:03:11 AM
I've been looking at worldview, here (https://go.nasa.gov/2zRTYNW) and here (https://go.nasa.gov/2U3yZPb) to try to figure out tidal movements. What I think I'm seeing is that according to atmospherics, mslp gradients and winds, differing amounts of Atl. water pass through Iceland/Scotland gap, it's temp. varies, some is short circuited and rounds Iceland joining Irminger current and eventually flowing up the west coast of Greenland, some heads north. It's progress north is again affected by atmospherics so can be somewhat erratic but the tides and currents slowly deliver it to either Fram or Barents by N.Z. . The fraction delivered deeper into Barents also divides some going into Kara and some sinking into St. Anna trough this is delivered into Nansen and pushes onwards across Gakel into Amundsen basin. This delivery sets up deep disturbences, internal waves, eddies and pulsed currents. The waves wash against Lomonosov and their reflections rebound causing turbulence that reaches the surface weakening the ice. The eddies get caught up in the trough by Gakel and turn east towards Laptev. It looks like a recent pulse was exceptional and caused a large series of radiated waves from somewhere near the center of the Siberian side of Amundsen.
Bremen AMSR2
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpuu.sh%2FFRI6a%2Fc93cb8a95e.jpg&hash=fdcb74f8b9ccf0994784f3eb33f40e27)
Title: Re: Tides
Post by: johnm33 on June 14, 2020, 10:30:55 AM
This is the same view as above but from amsr2 on polarview[010620], it's more subtle, hard to see the waves unless you know they're there.
(https://puu.sh/FWe01/45f8873845.jpg)
with that in mind a gif that starts on the 5th pauses/repeats where i see wave forms with the last image from yesterday [13020]
(https://media.giphy.com/media/JstPXkfkbUnCyNfMW2/giphy.gif)
What i suspect is happening is that the current dropping down St. Anna enhanced by tidal surges, and possibly river discharge, is causing resonant wave forms to set up in the depths of the Eurasian basin both across it and along it and at some point these 'spout out' 'https://www.youtube.com/watch?v=17IYhAt-2DE'  followed by a quieter period as that energy dissipates, probably starting tomorrow.
Title: Re: Tides
Post by: johnm33 on June 14, 2020, 10:40:13 AM
Link to 2mb version of gif. https://media.giphy.com/media/dx646cxS4aQ9spJvEJ/giphy.gif
Title: Re: Tides
Post by: johnm33 on June 18, 2020, 01:05:46 PM
This animation runs from  11:06 til' 17:06 it looks to me that another spouting out event happened in the deeper layers, so somewhat subdued compared to a surface event, but then the waves spread and have now subsided. Just in time for the build up of the next tidal acceleration of currents, that is if there's any 'reality' to my hypothesis.
(https://media.giphy.com/media/W6iEFPkBuTWEXGxy7u/giphy.gif)
There's a possibility that the wave action had some impact on the thinning showing up on Hycoms thickness
(https://media.giphy.com/media/UTBR3G9hmrH23WBB18/giphy.gif)
if that's the case then the ice will be slaughtered by the next event, if indeed there is one, so perhaps around  25:06 we see a 'peak' of losses on the eurasian side.
Title: Re: Tides
Post by: johnm33 on June 20, 2020, 12:11:26 PM
Parallel waves showed up on the 19:06 amsr2 just north of FJ suggesting the surge was on a much broader front than the above post implies, and todays sees that quashed possibly by outflow between FJ and SvBd, with the ice either side smashed by interacting waves. So tying that to the [uniquorns (https://forum.arctic-sea-ice.net/index.php?action=dlattach;topic=417.0;attach=127612;image)] bathymetry
(https://media.giphy.com/media/L2wrHcz2iRMurZl8Zc/giphy.gif)
If i find time i'll try to improve the gif.
Title: Re: Tides
Post by: uniquorn on June 25, 2020, 12:12:42 AM
https://os.copernicus.org/articles/14/225/2018/
North sea, not the arctic but perhaps still relevant
Quote
Tides are of fundamental importance for understanding shelf sea dynamics and ecosystems. Not only are tidal currents frequently the dominant flows in these regions (Otto et al., 1990), but the turbulence, bottom-mixing, and circulation patterns to which they give rise also have a profound effect on the physics, biogeochemistry, and ecology of shelf seas (Holt and Umlauf, 2008; Lenhart et al., 1995; Simpson and Hunter, 1974). In shallow regions with fast tidal currents, full-depth mixing is maintained throughout the year. In deeper regions or where tidal currents are slower, tidal mixing cannot overcome buoyancy forcing in summer and the water column stratifies seasonally. The boundaries between mixed and stratified areas are sharp (Hill et al., 2008) and are known as tidal mixing fronts. These fronts separate water masses with markedly different physical and biogeochemical properties, and the density-driven jets to which they give rise are important transport pathways (Hill et al., 2008). Consequently, understanding the processes that control the formation and location of tidal mixing fronts, alongside an accurate knowledge of the tidal currents themselves, is necessary for effective management of economically important shelf sea ecosystems and for modelling the dispersion of tracers, contaminants, and organisms.
Quote
2.2 Tidal ellipses

Tidal ellipses of the glider-derived tide show a decrease in the amplitude of zonal and meridional tidal velocity with distance offshore (Fig. 3a). Semi-major axes are consistently larger than semi-minor axes, and the offshore decrease in the magnitude of the semi-major axes is greater than the offshore decrease in semi-minor axes. The smaller rate of change in the eastern part of the section is because bathymetry gradients are smaller than in the west. Velocity amplitudes were multiplied by the mean water depth in each bin to derive ellipses of tidal transport per unit width (Fig. 3b). Compared with velocity amplitude, transport amplitude changes less markedly with distance offshore, suggesting that the greater tidal velocities observed in shallow water than in deep water are primarily a result of volume continuity rather than the exponential offshore decay of the tidal Kelvin wave.
Title: Re: Tides
Post by: uniquorn on July 01, 2020, 04:10:11 PM
Reposting here as this gif is showing Laptev ocean surface movement using infrared.
2 day loop, Lena delta in lower left, requires a click.  Shortwave infrared. Contrasted boosted for detail.

2m winds relatively constant from SE during the two days.
nullschool wind (https://earth.nullschool.net/#2020/06/29/2100Z/wind/surface/level/orthographic=-45.12,89.43,1146/loc=127.004,75.617)
Title: Re: Tides
Post by: johnm33 on July 03, 2020, 11:55:09 PM
The present and forecast mslp promises an increased inflow of Atl. waters, so both St. Anna and Franz Victoria troughs will see some action possibly as soon as 04:07 [07:04US] increased turbulence and forcing both along the Barents shelf and towards the pole, so maybe a [near] pole hole tues 07:07. Nares won't last that long, may have gone already, big tides will dislodge fast coastal ice and even if the wind changes the high slp should force enough water through to almost clear it next week.
I'm trying to make the case that the recent internal wave action in Beaufort was the resonant remains of the last full moons tides, if there's anything to that then we should see a repeat sometime around 23-25:07 trashing a much weaker Beaufort.
Title: Re: Tides
Post by: johnm33 on July 09, 2020, 09:47:53 AM
Looking at https://www.polarview.aq/arctic AMSR2 the damage by the tidal forcing of currents shows up well. This last full moon combined with high mslp has forced flow mainly towards St. Anna and the surges and vortices fed by that have damaged bottom ice, failed to open a pole hole but close, and now arguably the waves passing over/bouncing off Lomonosov are passing through and dissipating in the ocean to both sides. These may lead to secondary internal waves which will more likely show up as upwellings either by the coast or deeper shelves, how long these take to form and show remains opaque.
Title: Re: Tides
Post by: uniquorn on July 09, 2020, 09:41:13 PM
Not sure how much credence to give to the follow mosaic site (https://follow.mosaic-expedition.org/) but maybe this statement about tides will be confirmed by a paper at some point.
click to run
added P201 july drift.
Title: Re: Tides
Post by: blumenkraft on July 09, 2020, 09:54:25 PM
Uniquorn, i was wondering the same. I think this picture is shifted in perspective. No idea why they would do such a thing though.
Title: Re: Tides
Post by: uniquorn on July 09, 2020, 10:26:37 PM
Off topic, but that perspective makes PS look a lot further from the Fram Strait.
Title: Re: Tides
Post by: uniquorn on July 10, 2020, 10:18:21 AM
Might be applicable to wind driven drift..

What makes ships mysteriously slow down or even stop as they travel, even though their engines are working properly?

https://www.sciencedaily.com/releases/2020/07/200706152701.htm
Quote
This was first observed in 1893 and was described experimentally in 1904 without all the secrets of this "dead water" being understood. An interdisciplinary team from the CNRS and the University of Poitiers has explained this phenomenon for the first time: the speed changes in ships trapped in dead water are due to waves that act like an undulating conveyor belt on which the boats move back and forth. This work was published in PNAS on July 6, 2020.

In 1893, the Norwegian explorer Fridtjof Nansen experienced a strange phenomenon when he was travelling north of Siberia: his ship was slowed by a mysterious force and he could barely manoeuvre, let alone pick up normal speed. In 1904, the Swedish physicist and oceanographer Vagn Walfrid Ekman showed in a laboratory that waves formed under the surface at the interface between the salt water and freshwater layers that form the upper portion of this area of the Arctic Ocean interact with the ship, generating drag.

This phenomenon, called dead water, is seen in all seas and oceans where waters of different densities (because of salinity or temperature) mix. It denotes two drag phenomena observed by scientists. The first, Nansen wave-making drag, causes a constant, abnormally low speed. The second, Ekman wave-making drag, is characterized by speed oscillations in the trapped boat. The cause of this was unknown. Physicists, fluid mechanics experts, and mathematicians at the CNRS' Institut Pprime and the Laboratoire de Mathématiques et Applications (CNRS/Université de Poitiers) have attempted to solve this mystery. They used a mathematical classification of different internal waves and analysis of experimental images at the sub-pixel scale, a first.

This work showed that these speed variations are due to the generation of specific waves that act as an undulating conveyor belt on which the ship moves back and forth. The scientists have also reconciled the observations of both Nansen and Ekman. They have shown that the Ekman oscillating regime is only temporary: the ship ends up escaping and reaches the constant Nansen speed.

This work is part of a major project investigating why, during the Battle of Actium (31 BC), Cleopatra's large ships lost when they faced Octavian's weaker vessels. Might the Bay of Actium, which has all the characteristics of a fjord, have trapped the Queen of Egypt's fleet in dead water? So now we have another hypothesis to explain this resounding defeat, that in antiquity was attributed to remoras, 'suckerfish' attached to their hulls, as the legend goes.

The dual nature of the dead-water phenomenology: Nansen versus Ekman wave-making drags.
Johan Fourdrinoy, Julien Dambrine, Madalina Petcu, Morgan Pierre, and Germain Rousseaux.
PNAS, 2020 DOI: 10.1073/pnas.1922584117
Quote
A ship evolving in a stratified fluid is sometimes slowed down in comparison to a homogeneous case. This dead-water phenomenon was reported by the Norwegian explorer Fridtjöf Nansen during his North polar expedition in 1893. The physicist and oceanographer Vagn Walfrid Ekman was the first to study in the laboratory the physical origin of dead-water phenomenon in 1904: at the interface between saline water and freshwater, internal gravity waves appear, propagate, and generate a wave-making drag. Here we show that the velocity oscillations of pulled ships models à la Ekman caught in dead water are due to a transient internal dispersive undulating depression produced during the initial acceleration of the ship that we predict with a linear analytical model.

Abstract

A ship encounters a higher drag in a stratified fluid compared to a homogeneous one. Grouped under the same “dead-water” vocabulary, two wave-making resistance phenomena have been historically reported. The first, the Nansen wave-making drag, generates a stationary internal wake which produces a kinematic drag with a noticeable hysteresis. The second, the Ekman wave-making drag, is characterized by velocity oscillations caused by a dynamical resistance whose origin is still unclear. The latter has been justified previously by a periodic emission of nonlinear internal waves. Here we show that these speed variations are due to the generation of an internal dispersive undulating depression produced during the initial acceleration of the ship within a linear regime. The dispersive undulating depression front and its subsequent whelps act as a bumpy treadmill on which the ship would move back and forth. We provide an analytical description of the coupled dynamics of the ship and the wave, which demonstrates the unsteady motion of the ship. Thanks to dynamic calculations substantiated by laboratory experiments, we prove that this oscillating regime is only temporary: the ship will escape the transient Ekman regime while maintaining its propulsion force, reaching the asymptotic Nansen limit. In addition, we show that the lateral confinement, often imposed by experimental setups or in harbors and locks, exacerbates oscillations and modifies the asymptotic speed.
Title: Re: Tides
Post by: johnm33 on July 10, 2020, 11:22:20 PM
Gif covers first to tenth, what are the odds that the spread of secondary waves wash up against Greenland/Ellesmere making the following days somewhat like the first?
(https://media.giphy.com/media/MC3HznPuC8H0pUHfkX/giphy.gif)
Title: Re: Tides
Post by: johnm33 on July 16, 2020, 10:23:39 PM
The build up of the next tidal cycle begins, the atmospherics are set well to get Atl. waters north of the Faroes, from here the most enerjetic waters will head for Norways coast then up into Barents so by 18:07 we should see[?] accelerated flow through St. Anna. With such a long established stable high and the winds slowing the ice easing it towards the center there may have been time for a current to form taking the excess mass of water beneath that high towards Fram, if thats the case then in about ten days we may see a 'river' of melt moving from the ESS towards Fram, and vaguely possible that it's already begun from the last surge.
If my guess about the Internal waves arriving at Greenland/Ellesmere was valid then the recent gap should close again soon, though that may be affected by the beginnings of rotation in the pack being accelerated by tides in Amundsen gulf pushing water/ice towards Chukchi, in which case the danger to the CAA increases due to more Atl. penetration.
The outer ice blocking 79N/Zach. is looking weak so maybe by tuesday some action there too, also the waters in Disko are very warm and there's nothing to stop large exchanges of freshwater from beneath Jacobshavn with it, though it's difficult to imagine anything more than accelerated calving there.
Title: Re: Tides
Post by: uniquorn on July 19, 2020, 11:39:55 AM
Reposting JayW animation for reference.
Title: Re: Tides
Post by: johnm33 on August 01, 2020, 03:46:20 PM
One of the gifs is big the other huge gone, just to illustrate the tidal surge into Barentz and the almost coincidental suction in the Greenland sea.
added a link (https://giphy.com/gifs/fYT63Cq7JjGKourprU) to the big gif  a link (https://view.marine.copernicus.eu/ViewService/?permalinking=true&bgmap=Blue%20Marble%20North%20Polar&dataset=http://nrt.cmems-du.eu/thredds/wms/dataset-topaz6-arc-15min-3km-be&numColorBands=250&logScale=false&bbox=-4852294.921875,-3136637.5274957,8790283.203125,6785237.4725043&abovemaxcolor=0x000000&belowmincolor=0x000000&nodatacolor=null&layer=zos&time=2020-08-02T00%253A00%253A00.000Z&palette=rainbow&style=boxfill&scaleRange=-1.5,1.5&displayScaleRange=-1.5,1.5&opacity=1&record_id=319140a0-f18d-4ae2-9e6c-552d653e32c8&dataset_id=Arctic%20Ocean%20Physics%20Analysis%20and%20Forecast,%203%20km%20quarter-hourly%20instantaneous%20(dataset-topaz6-tide-arc-qhr-myoceanv2-be)) to where you can either look at the current state of tides or make your own gif the large one is only three days! What these show is surface height above geoid.
Title: Re: Tides
Post by: blumenkraft on August 03, 2020, 12:47:24 PM
My take on the loss of ice north of Greenland is tidally forced Atl. entering by Svalbard enhancing the existing current towards Nares of the same waters but pushing more forcefully along the shelf creating turbulence/vortices which overspill onto the shelf. Not all of it makes it through to the Canadian side but may force it's way through in the two or three days left of peak tidal movement, after that the rotating ice should close the gap. Similarly the lighter fraction of Atl. waters is creating more turbulence along Barents shelf as it pushes east causing more melt/retreat there.

BTW, yesterday's tidal wave coming from the NS spread out straight north.

Click to play.
Title: Re: Tides
Post by: oren on August 03, 2020, 01:03:02 PM
I normally use Occam's razor. When a warm wind is consistently blowing from the south for days on end, it is quite clear that it is to blame for ice retreat and melt north of Greenland. The tides are always there doing their bits with eddies and some fast ice breakup (e.g. in the CAA) but the ice north of Greenland does not melt and retreat north every summer.
Title: Re: Tides
Post by: blumenkraft on August 03, 2020, 01:15:56 PM
And how come that your tides only work one way?

Well, i see this tidal wave propagating only north along the Greenland shoreline, not south. (Sorry, i placed the circle a bit too north and made it way too big, but i hope you know what i mean.)

48 frames, stills skipped. Click to play.

Title: Re: Tides
Post by: uniquorn on August 03, 2020, 01:57:49 PM
<>The tides are always there doing their bits with eddies and some fast ice breakup (e.g. in the CAA) but the ice north of Greenland does not melt and retreat north every summer.
I expect that shelf break melt will become a more accepted part of the melting season as the arctic moves to a higher percentage FYI. Without a constant supply of MYI, north of Greenland could start to look more like north of FJL/Svalbard, dependent on wind direction.
Unfortunately there is only a buoy swarm in the Fram at the moment. Most viewers will be able to detect non negligible tidal movement. For me this disproves the theory that tides just go up and down with a negligible tidal current that has no effect on ice. There is, to me, clearly a more circular motion involved, suggesting eddies and mixing that would affect ice melt, particularly at shelf breaks, where the underlying slope of the ocean floor likely amplifies the turbulence.
These buoys are over 250km from nearest land

shelf break image from http://mseas.mit.edu/Research/MOPE/index.html  (not arctic but shows some of the processes)

added gif from http://rob-hetland.blogspot.com/2005/04/shelf-break-front-simulation.html
Quote
Shelf break front simulation
Here is a sample cross-section from an idealized shelf break front simulation. The contours are salinity, the colorfill velocity.
This is exactly the kind of movement seen in the FJL/Svalbard gap.  click
rammb example here (https://forum.arctic-sea-ice.net/index.php/topic,2417.msg246318.html#msg246318)
Title: Re: Tides
Post by: binntho on August 03, 2020, 02:14:45 PM
And how come that your tides only work one way?

Well, i see this tidal wave propagating only north along the Greenland shoreline, not south. (Sorry, i placed the circle a bit too north and made it way too big, but i hope you know what i mean.)

48 frames, stills skipped. Click to play.

Good gif!

I have been thinking a bit about the words we use in the context of tides. There seems to be some confusion, for instance what do we mean by "wave"?

The wave we see in your gif is a pressure wave. It is a very localized and probably secondary effect of the Nares tidal movement. We can also see some actual back-and-forth movement of near-shore ice.

In the Nares, water flows back and forth, 5 km3 the one way and 5 km3 the other way, twice daily. A pressure wave is more likely to originate when water exits a narrow strait, rather than when water enters in corresponding amounts. But if a pressure wave had it's origins at he mouth of the Nares it should propagate into the Lincoln sea, in a very wide front, losing energy very quickly.

The wave in your gif is, as stated earlier, very small and localized, and far from Nares as well. So I'd guess that there is some near-coastal bathymetric structure where the pressure wave originates as a result of the presumed diurnal current coming out of Nares and most likely turning towards the Greenland coast - and going both ways, as can be seen in the movement of near-shore ice. A back-and-forth current, and a pressure wave front resulting from some interference with coastal and/or bathymetric features.
Title: Re: Tides
Post by: blumenkraft on August 03, 2020, 02:59:20 PM
Binntho, maybe tidal wave is the wrong word, i give you that. The tides move floes back and forth, i agree on that (obviously ;)).

Can we agree on the following?

The pressure wave is the result, the tide is the cause. The pressure wave is influenced by bathymetry. The bathymetry makes it so that the pressure wave propagates in one direction - not back and forth.
Title: Re: Tides
Post by: binntho on August 03, 2020, 03:04:02 PM
Binntho, maybe tidal wave is the wrong word, i give you that. The tides move floes back and forth, i agree on that (obviously ;)).

Can we agree on the following?

The pressure wave is the result, the tide is the cause. The pressure wave is influenced by bathymetry. The bathymetry makes it so that the pressure wave propagates in one direction - not back and forth.

It seems we are in total agreement!
Title: Re: Tides
Post by: blumenkraft on August 03, 2020, 03:07:04 PM
Cool! CloolCoolCool! :)
Title: Re: Tides
Post by: johnm33 on August 03, 2020, 06:19:11 PM
"all one way" the distinction i make is that due to residual tangential energy in the Atl. waters by the time the peak of the tides move south the bulk of that [Atl.] water is elsewhere so is replaced by Arctic waters displaced by incoming Atl. waters. This is evidenced by the incoming holding fast to either the continent, the Barents shelf or the deeper parts of Barents, and equally by the water flowing south holding fast against Greenland due to it's deficit of tangential inertia. Looking further south the peak of the tide passing through the gap by the Faroes proceeds in the 'wrong' direction whilst the Atlantic continues it's ac rotation onto Baffin, i think that motion too is related to the residual inertia within the Atl. waters forcing them to the right.
Title: Re: Tides
Post by: johnm33 on August 03, 2020, 08:03:40 PM
To Orens point, the tides are always present and they really aren't very large but at Bear island for instance they can vary between a range of .3m to .8 that is at their weakest the range is .3m between high and low and can be as much as .8m between high and low. There are other variables but if both happened in otherwise similar circumstances it suggests the amount of Atl. waters delivered can double/halve, and the tides wax and wane so it's never a one off event, i look at it as events spread over a week to 10 days around the peak since the prevailing conditions throughout affect any particular tide which can reinforce or cancel previous forcings.
Another point for binntho, the peak wave travelling down the Greenland coast almost coincides with the peak moving north by Norway.
Title: Re: Tides
Post by: oren on August 03, 2020, 09:42:22 PM
To be clear I believe tides play a very important role in the Arctic. However I don't think this role is very different this year from other years, at least not with the mganitude required to explain the crazy open water north of Greenland. To explain that we have the anomalous persistent wind from the south, along with received insolation during July, high temps and upwelling.
Title: Re: Tides
Post by: binntho on August 04, 2020, 03:08:36 AM
John, you keep claiming that the tides move a lot of water = and I men a lot. Your posts imply  at least hundreds of km3 if not thousands. This should be easily verifiable, these seas have been measured for decades if not centuries.

In "The 2020 melting season" thread yesterday I posted links to two recent research papers, one that specifically measured tidal movement in the Nares strait (https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018JC014122) which I estimated to be in the range of 5 km3 twice daily, very insignificant at the scale of the Arctic ocean, but big enough to cause tidal currents to be visible along the coast of Greenland.  (First post (https://forum.arctic-sea-ice.net/index.php/topic,3017.msg279085.html#msg279085))

But the tidal effect in the Nares is quite big - the tidal effect elsewhere is very small, and within the Arctic ocean itself it is not really discernible. Another paper I linked to yesterday measured current flows in the Fram strait (https://www.researchgate.net/publication/332171700_Deep_Flow_Variability_Offshore_South-West_Svalbard_Fram_Strait). They are strong, and they vary, but there is no tidal factor mentioned, simply because the tides do not effect the flow of water throught the Fram strait. (Second post (https://forum.arctic-sea-ice.net/index.php/topic,3017.msg279127.html#msg279127))

So I challenge you to show one single paper that measures or calculates the phenomena you keep posting about. Specifically you keep making statements that imply the movement of vast amounts of water with the all the turbulence and whatnot that such movement would induce. But you show no evidence whatsoever!

John, making repeated claims about strange phenomena that nobody else sees or can measure, is called pseudoscience. And Oren, I challenge you to be stricter in moderation here - John should not be allowed to post pseudoscientific claims on the main threads as if they were accepted science. Until he can bring evidence, as in real life measurements or scientifically sound modelling and calculations, the whole tidal fixation has to be deemed pseudoscience.

Comments like "I believe tides play a very important role in the Arctic" are not helpful here. If you think they are so very important, where is the evidence? Where are the scientific papers about this important role? What are the physics behind it, and how does it work, and how comes nobody has measured it or written about it?
Title: Re: Tides
Post by: Rod on August 04, 2020, 03:58:16 AM

So I challenge you to show one single paper that measures or calculates the phenomena you keep posting about. Specifically you keep making statements that imply the movement of vast amounts of water with the all the turbulence and whatnot that such movement would induce. But you show no evidence whatsoever!

Tides stir up deep Atlantic heat in the Arctic Ocean

Quote
Researchers have identified how warm Atlantic water that is flowing deep into the Arctic Ocean is mixing with colder waters above to contribute to sea-ice loss in the Arctic. The results, published this week in the journal Nature Geoscience, show that tidal flows in the Arctic are causing deep, warm water (originating from the Gulf Stream) to mix with cold, fresh water lying above, in turn contributing to melting the floating sea-ice.

                                                                 .   .   . 

Quote
We studied the warm body of water from the Atlantic that represents the largest oceanic input of heat into the Arctic – it is four degrees Celsius warmer than the surrounding water, and it is the warmest it has been in nearly two thousand years. The top of the warm layer sits at depths between 40 and 200 m, and its heat slowly diffuses upwards into the cold, fresher water above, but sometimes this movement of heat can be greatly accelerated by turbulence which drives mixing. We have found that tides are producing significant amounts of turbulence over steep sea bed topography, and so are greatly enhancing the upward movement of heat in these regions. In areas where tidal currents interact with steep sea bed slopes, this process causes mixing of the warmer waters with the over-lying colder waters, and this in turn can generate 'hotspots' for sea-ice melt or thinning.

https://www.google.com/amp/s/phys.org/news/2015-02-tides-deep-atlantic-arctic-ocean.amp

Title: Re: Tides
Post by: oren on August 04, 2020, 04:15:25 AM
Quote
If you think tides are so very important, where is the evidence?
I have seen enough RAMBB and Mosaic animations showing effects of tides, including in the CAA where the tides break some of the fast ice. It is clear to me that tides add kinetic energy to the system, and also do move water around, presumably by ratcheting on the bathymetry and/or on Coriolis effects.
By how much? I have no clue. Scientific papers? I welcome them.

Quote
John should not be allowed to post claims on the main threads as if they were accepted science
I admit I have trouble sometimes following John's hydrological explanations, though I've been reading them for years. It can be very profound or it can be wrong, I am mostly unable to judge. Over time I have poked some questions and have gleaned some insights but not enough. This is why I encourage debates to be held on the Tides thread, to shed light on this important issue.
As for moderation, where I judge claims to be unsupported I will tend to act. However where I judge posts to be harmless (i.e. no specific claims can be discerned, or writeup is too esoteric to be controversial) I will tend to keep them even when I can't judge them.
If you have trouble with specific posts that you believe cause some harm, please do use Report to Moderator and explain. I always pay attention to these reports, and often act on them.
Title: Re: Tides
Post by: binntho on August 04, 2020, 06:59:47 AM
Oren, thanks for the reply. But the examples you give and we all have seen do not imply a "very important role" outside of a very small area, i.e. the Nares, the Lincoln Sea coast of Greenland, and some areas in the CAA. So yes, in certain isolated places the tides do impart kinetic energy. That does not equate to a "very important role" for the entire Arctic.

Rod, the article you linked to is excellent and I must admit that it surprises me that the weak Arctic tides (as they point out themselves) can have so profound an impact. But the article does no no way whatsoever support John's various claims.

To repeat: The article does not support John's posts.
Title: Re: Tides
Post by: binntho on August 04, 2020, 07:03:31 AM
Oren, here is a recent example from the main thread. One I replied to on the main thread, but would have ignored in this thread.

My take on the loss of ice north of Greenland is tidally forced Atl. entering by Svalbard enhancing the existing current towards Nares of the same waters but pushing more forcefully along the shelf creating turbulence/vortices which overspill onto the shelf. Not all of it makes it through to the Canadian side but may force it's way through in the two or three days left of peak tidal movement, after that the rotating ice should close the gap. Similarly the lighter fraction of Atl. waters is creating more turbulence along Barents shelf as it pushes east causing more melt/retreat there.

He does start with "my take" but for those unfamiliar with the steady stream of pseudoscience from him it may create the impression that totally freeform musings without scientific grounding are allowed as part of normal discourse.
Title: Re: Tides
Post by: blumenkraft on August 04, 2020, 07:05:47 AM
Quote from: Oren
This is why I encourage debates to be held on the Tides thread, to shed light on this important issue.

+1

He is onto something IMHO. I also don't understand it completely quite yet, but i would like to.
Title: Re: Tides
Post by: binntho on August 04, 2020, 07:08:15 AM
Rod, further to your article. In the Abstract they say:

Quote
Vertical mixing is generally weak within the Arctic Ocean basins, with very modest heat fluxes...

but that at certain isolated locations

Quote
... geographically limited observations have indicated substantially enhanced turbulent mixing rates over rough topography.

and

Quote
We identify tides as the main energy source that supports the enhanced dissipation

So in geographically isolated regions, heat flux is enhanced by tidal-induced turbulence. But there is no indication that this is a widespread phenomenon and if it has any measurable impact on the total sea ice cover. I exptect it does, there are polynia and bites that are suspiciously ice free, and some of them may be caused by this effect. But without the full article, it's very hard to say.

And again, the article does in no way whatsoever support John's claims.
Title: Re: Tides
Post by: binntho on August 04, 2020, 07:09:18 AM
This is why I encourage debates to be held on the Tides thread, to shed light on this important issue.

+1

He is onto something IMHO. I also don't understand it completely quite yet, but i would like to.
I think it was Oren who said that - and yes, debates about tides are interesting. But battling pseudoscientists with fixed ideas is not good for the blood pressure!  8)
Title: Re: Tides
Post by: binntho on August 04, 2020, 07:16:23 AM
Searching for an open-source copy of Rod's article I found the following:

Tidal Conversion and Mixing Poleward of the Critical Latitude (an Arctic Case Study) (https://agupubs.onlinelibrary.wiley.com/doi/pdfdirect/10.1002/2017GL075310)

It's an interesting article, and in the abstract they say that although tidal energy is a major source of turbulence mixing in the world's oceans, north of the "critical latitude", Coriolis forces make propagation of linear tides impossible.

Quote
... much of the Arctic Ocean is north of the critical latitude, beyond which the type of
 nternal tide that is believed to drive mixing across other major oceans on the planet cannot occur.

So effectively, John's ideas are shot down - the Coriolis force precludes the effects he thinks he is seeing.

Other than that the article seems to be saying the same thing as the one Rod pointed out, that in spite of this, some turbulence does occur:

Quote
However, new evidence has been found that suggests that the tide might be important in driving mixing in certain areas of the Arctic Ocean.
Title: Re: Tides
Post by: blumenkraft on August 04, 2020, 07:29:52 AM
I think it was Oren who said that - and yes, debates about tides are interesting. But battling pseudoscientists with fixed ideas is not good for the blood pressure!  8)

Sorry, fixed. Hadn't had my first coffee yet. ;)

On your point though, it's not pseudoscience. It's talking about observations made. This is 100% legit.
Title: Re: Tides
Post by: binntho on August 04, 2020, 08:05:08 AM
I think it was Oren who said that - and yes, debates about tides are interesting. But battling pseudoscientists with fixed ideas is not good for the blood pressure!  8)

Sorry, fixed. Hadn't had my first coffee yet. ;)

On your point though, it's not pseudoscience. It's talking about observations made. This is 100% legit.

Writing from the land of coffee, I fully appreciate your need for the fix!

But I disagree that it is not pseudoscience if it is based on observations. We can all observe things, but the science bit is in the underlying mechanisms, forces and processes.

Two recent examples are a gif John posted which showed ice moving back and forth north of Svalbard, along with claims about tidal movements (in an area almost totally devoid of tidal effect) while the obvious explanation was that it was wind driven!

And the other example is that the gap opening up north of Greenland is somehow due to tidal forcings while again it is obviously due to winds and warm air advection.

So he sees things and uses his imagination to come up with pseduoscientific explanations. Science is when you have numbers, measurements, quantifiable observations and verifiable predictions. He has none of that.
Title: Re: Tides
Post by: KiwiGriff on August 04, 2020, 08:09:30 AM
(https://arctickoalablog.files.wordpress.com/2016/08/map_labels3.png)
I am with binntho... Again.
Tides are not a significant influence in the Arctic ocean.
In deeper water over 20m or so tidal flows do not have much if any effect.
Wave and swell action are far more significant at such depths.
Fifty odd years of pissing around in boats and  many hours scuba diving reinforces my views.
Unless tidal flows are constrained by topography the effects  are insignificant.
Title: Re: Tides
Post by: uniquorn on August 04, 2020, 09:24:30 AM
In my humble opinion, mosaic buoys are showing tidal movement that affects melt. They have been showing it ever since the project started. Tidal movement is less detectable further north. Some people see it, some don't, and some don't want to see it.
The ICEX buoys may show it too when I zoom in on them later.
Title: Re: Tides
Post by: binntho on August 04, 2020, 09:46:14 AM
In my humble opinion, mosaic buoys are showing tidal movement that affects melt. They have been showing it ever since the project started. Tidal movement is less detectable further north. Some people see it, some don't, and some don't want to see it.
The ICEX buoys may show it too when I zoom in on them later.

There are two statements here that would need substantiation:

1) The buoys show tidal movement.
2) The tidal movement affects melt.

Perhaps some data to support these statements?
Title: Re: Tides
Post by: uniquorn on August 04, 2020, 09:50:26 AM
Wasn't this (https://forum.arctic-sea-ice.net/index.php/topic,3030.msg260724.html#msg260724) enough for 1)?
Perhaps JayW's gif (https://forum.arctic-sea-ice.net/index.php/topic,3030.msg275257.html#msg275257), also northern Laptev, from jul19 2020 for 2)
Both already on this thread.
Title: Re: Tides
Post by: blumenkraft on August 04, 2020, 09:54:49 AM
Perhaps some data to support these statements?

Uniquorn's posts are 99.9999% data. Valuable data mind you! Telling him to post data is a bold move. Not at all a clever move, but a bold one.
Title: Re: Tides
Post by: binntho on August 04, 2020, 10:11:37 AM
Wasn't this enough for 1?
https://forum.arctic-sea-ice.net/index.php/topic,3030.msg260724.html#msg260724
Good animation. I've not been following this thread, trying to keeping my bloodpressure down, but the tidal movement is very clear. Five days (less 2 hours) with 10 loops. Total distance travelled is 67km and the magnitude of each sideways movement is around 1km to each side.

Not very much, and perhaps not unexpected over deep ocean. Do you see something similar over other parts of the Arctic or only over the Lomonosov?

This of course does not in any way substantiate what John has been claiming.
Title: Re: Tides
Post by: uniquorn on August 04, 2020, 10:17:18 AM
mosaic buoys over the yermak plateau (https://forum.arctic-sea-ice.net/index.php/topic,2906.msg270057.html#msg270057) from the mosaic thread.

rammb (https://forum.arctic-sea-ice.net/index.php/topic,2906.msg276517.html#msg276517) of yermak/fram. I'm not claiming that is all tidal but similar movement suggest a tidal contribution.
Title: Re: Tides
Post by: binntho on August 04, 2020, 11:01:19 AM
The tidal movement in the first gif was a measly 1km per 6 hours, and the same the other way Average speed 4.5 cm/s, significantly lower than in the Nares strait. Unless there are great differences in the rate of movement from one area to another, I can't really see it affecting the ice at all. In other words, the ice probably simply shifts back and forth by a tiny amount, with far less effect than a moderate wind would have.
Title: Re: Tides
Post by: uniquorn on August 04, 2020, 11:03:19 AM
Understood, we disagree.  :) Thank you for accepting that there is some tidal movement. My interest is mostly at the shelf breaks, where that measly movement might be amplified by the rapid change in depth.
Title: Re: Tides
Post by: johnm33 on August 09, 2020, 04:20:37 PM
John, you keep claiming that the tides move a lot of water = and I men a lot. Your posts imply  at least hundreds of km3 if not thousands. This should be easily verifiable, these seas have been measured for decades if not centuries.

In "The 2020 melting season" thread yesterday I posted links to two recent research papers, one that specifically measured tidal movement in the Nares strait (https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018JC014122) which I estimated to be in the range of 5 km3 twice daily, very insignificant at the scale of the Arctic ocean, but big enough to cause tidal currents to be visible along the coast of Greenland.  (First post (https://forum.arctic-sea-ice.net/index.php/topic,3017.msg279085.html#msg279085))

But the tidal effect in the Nares is quite big - the tidal effect elsewhere is very small, and within the Arctic ocean itself it is not really discernible. Another paper I linked to yesterday measured current flows in the Fram strait (https://www.researchgate.net/publication/332171700_Deep_Flow_Variability_Offshore_South-West_Svalbard_Fram_Strait). They are strong, and they vary, but there is no tidal factor mentioned, simply because the tides do not effect the flow of water throught the Fram strait. (Second post (https://forum.arctic-sea-ice.net/index.php/topic,3017.msg279127.html#msg279127))

So I challenge you to show one single paper that measures or calculates the phenomena you keep posting about. Specifically you keep making statements that imply the movement of vast amounts of water with the all the turbulence and whatnot that such movement would induce. But you show no evidence whatsoever!

John, making repeated claims about strange phenomena that nobody else sees or can measure, is called pseudoscience. And Oren, I challenge you to be stricter in moderation here - John should not be allowed to post pseudoscientific claims on the main threads as if they were accepted science. Until he can bring evidence, as in real life measurements or scientifically sound modelling and calculations, the whole tidal fixation has to be deemed pseudoscience.

Comments like "I believe tides play a very important role in the Arctic" are not helpful here. If you think they are so very important, where is the evidence? Where are the scientific papers about this important role? What are the physics behind it, and how does it work, and how comes nobody has measured it or written about it?
"keep claiming" I did once estimate the amount of water I thought moved through the Norwegian/Greenland seas as best I recall it was a similar order of magnitude to your paper says moves through Nares so unless you can be specific I don't know what you're talking about.
On the south west coast of Svalbard I would anticipate the norhward flowing current to somewhat flatten against the shelf, as it has to shed about 4mph for every deg. it moves north and as it's essentially weightless it moves here more like a vertical stream which accounts for the turbidity. I don't use 'coriolis force' to think with since it is deemed to be fictional, instead I use tangential speed and assume some ongoing normalisation to 'current' latitude this means of course that any waters flowing out from the Arctic will naturally have a lower inherent tangential speed will lose ground turn right and explore the Greenland fjords rather than the S.W. Svalbard coast.
from the paper " It is not  entirely  clear to  what  extent  the  increased  heat  transport  toward  the  Arctic  is  related to  a strengthening of the Atlantic Meridional Overturning Circulation [32], to an increase in temperature or in volume of  the  AW  [4,33],  or,  instead, to  the  variability  of  the AW  transport along the two preferential pathways (Barents Sea and Fram Strait branches, [33]). Notably, the AW heat transport [29,34] can affect air temperature especially during winter [35], which in turn has direct effects on the dense water formation around the Spitsbergen margin. "
Personally i think the prime suspect is the gradual overcoming of the inertia of the Arctic ocean, that is it begins to wake from a long slumber and currents push more easily into it and in turn force out Arctic waters, but bear in mind this is just from observation and thought so in some sense 'made up'.
I have tried to find a paper which quantifies the amount of water moved around by tides in the Atlantic without success, even tried a calculation myself but didn't find the number credible so if anyone knows of such a paper I'd be grateful, or even an apropriate search term would help.
    Now although I have read quite a bit about tides in the last few years i found nothing that elucidates your insight "The physics of course is that the tidal effect is caused by expansion of water in the deep ocean at lower latitudes, with minimal actual movement of water except where coastal obstruction creates a local height/gravity imbalance (a fancy way of saying "downward slope")."  from (https://forum.arctic-sea-ice.net/index.php/topic,2923.0.html) do you know of a paper?
Title: Re: Tides
Post by: binntho on August 09, 2020, 07:04:51 PM
I don't use 'coriolis force' to think with since it is deemed to be fictional,

Well, that says it all. John, please stop posting until you have learned some science!
Title: Re: Tides
Post by: uniquorn on August 09, 2020, 08:50:01 PM
https://en.wikipedia.org/wiki/Fictitious_force
Quote
Fictitious force
From Wikipedia, the free encyclopedia
A fictitious force (also called a pseudo force,[1] d'Alembert force,[2][3] or inertial force[4][5]) is a force that appears to act on a mass whose motion is described using a non-inertial frame of reference, such as an accelerating or rotating reference frame. An example is seen in a passenger vehicle that is accelerating in the forward direction - passengers perceive that they are acted upon by a force in the rearward direction pushing them back into their seats. An example in a rotating reference frame is the force that appears to push objects outwards towards the rim of a centrifuge. These apparent forces are examples of fictitious forces.

The fictitious force F is due to an object's inertia when the reference frame does not move inertially, and thus begins to accelerate relative to the free object. The fictitious force thus does not arise from any physical interaction between two objects, such as electromagnetism or contact forces, but rather from the acceleration a of the non-inertial reference frame itself, which from the viewpoint of the frame now appears to be an acceleration of the object instead, requiring a "force" to make this happen. As stated by Iro:[6][7]

    Such an additional force due to nonuniform relative motion of two reference frames is called a pseudo-force.
    — H. Iro in A Modern Approach to Classical Mechanics p. 180

Assuming Newton's second law in the form F = ma, fictitious forces are always proportional to the mass m.

The fictitious force on an object arises as an imaginary influence, when the frame of reference used to describe the object's motion is accelerating compared to a non-accelerating frame. The fictitious force "explains," using Newton's mechanics, why an object does not follow Newton's laws and "floats freely" as if weightless. As a frame can accelerate in any arbitrary way, so can fictitious forces be as arbitrary (but only in direct response to the acceleration of the frame). However, four fictitious forces are defined for frames accelerated in commonly occurring ways: one caused by any relative acceleration of the origin in a straight line (rectilinear acceleration);[8] two involving rotation: centrifugal force and Coriolis force; and a fourth, called the Euler force, caused by a variable rate of rotation, should that occur.

Gravitational force would also be a fictitious force based upon a field model in which particles distort spacetime due to their mass, such as general relativity.
Quote
Fictitious forces and work

Fictitious forces can be considered to do work, provided that they move an object on a trajectory that changes its energy from potential to kinetic. For example, consider a person in a rotating chair holding a weight in their outstretched hand. If they pull their hand inward toward their body, from the perspective of the rotating reference frame, they have done work against the centrifugal force. When the weight is let go, it spontaneously flies outward relative to the rotating reference frame, because the centrifugal force does work on the object, converting its potential energy into kinetic. From an inertial viewpoint, of course, the object flies away from them because it is suddenly allowed to move in a straight line. This illustrates that the work done, like the total potential and kinetic energy of an object, can be different in a non-inertial frame than an inertial one.


Gravity as a fictitious force
Main article: General relativity
The notion of "fictitious force" comes up in Einstein's general theory of relativity.[17][18] All fictitious forces are proportional to the mass of the object upon which they act, which is also true for gravity.[19] This led Albert Einstein to wonder whether gravity was a fictitious force as well. He noted that a freefalling observer in a closed box would not be able to detect the force of gravity; hence, freefalling reference frames are equivalent to an inertial reference frame (the equivalence principle). Following up on this insight, Einstein was able to formulate a theory with gravity as a fictitious force and attributing the apparent acceleration of gravity to the curvature of spacetime. This idea underlies Einstein's theory of general relativity. See Eötvös experiment.
Title: Re: Tides
Post by: johnm33 on August 09, 2020, 10:14:00 PM
"Fictitious force" my point is that's a headful of itself, so to be able to think about it I take the tangential speed at 60N [500mph] -the same at the pole [0mph] divide that into the mileage, 2000 and get about 4mph to shed/gain per deg. of N/S movement which is just the inertial component, very real and very simple. The angular momentum component I address in a different manner assuming that any movement N/S is going to force a rotation in any current, somewhat like the magnetic force around an electric cable, but which apparently can come to dominate temporarily the motion of the current when a change of direction is forced, whatever that forced change is. Thus if it turns right into a fjord turbulence, if it is forced to flatten against a shelf vortices form in the vertical current, and if it meets a wall of water, going north it will form vortices which try to go up and south the opposite. The angular momentum is interesting but the inertia if it is not going into motion where it actually is is forcing motion somewhere in the direction it's headed, thus as the Arctic 'wakes' the currents in the Norwegian sea will more closely approach that 4mph, which makes the inertia more significant, i think?
Title: Re: Tides
Post by: binntho on August 10, 2020, 06:41:19 AM
Uniqorn, you have just demonstrated how truly lost poor John is. But if he wants to continue free-form fantasy postings in this thread he is welcome. But the "real"  threads are not the place for pseudoscience.
Title: Re: Tides
Post by: KiwiGriff on August 10, 2020, 07:49:10 AM
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015JC011009
Abstract
Seismic reflection imaging of mixing processes in Fram Strait
Quote
The West Spitsbergen Current, which flows northward along the western Svalbard continental slope, transports warm and saline Atlantic water (AW) into the Arctic Ocean. A combined analysis of high‐resolution seismic images and hydrographic sections across this current has uncovered the oceanographic processes involved in horizontal and vertical mixing of AW. At the shelf break, where a strong horizontal temperature gradient exists east of the warmest AW, isopycnal interleaving of warm AW and surrounding colder waters is observed. Strong seismic reflections characterize these interleaving features, with a negative polarity reflection arising from an interface of warm water overlying colder water. A seismic‐derived sound speed image reveals the extent and lateral continuity of such interleaving layers. There is evidence of obliquely aligned internal waves emanating from the slope at 450–500 m. They follow the predicted trajectory of internal S2 tidal waves and can promote vertical mixing between Atlantic and Arctic‐origin waters.
Well above my pay grade but I think relevant to the discussion.


Illustration of Tidal influences in the arctic .
From
Ocean Tide Influences on the Antarctic and Greenland Ice Sheets
Laurie Padman  Matthew R. Siegfried  Helen A. Fricker
First published: 08 January 2018

 (https://agupubs.onlinelibrary.wiley.com/cms/asset/1a557e7f-db33-4215-99e4-60814270f709/rog20157-fig-0001-m.jpg)
Figure 1

Global tidal properties derived from the TPXO‐7.2 global inverse tide model, an update to Egbert and Erofeeva (2002). (a) Tidal range (m), defined as maximum surface tide height minus minimum height over 1 year. Sites identified as 1–6 show locations for which the sea surface height amplitudes for the major tidal constituents are given in Table 1. (b) Mean tidal current (m s−1), defined as the annual average of instantaneous tidal speed, |u | = (u 2 + v 2)1/2, where u and v are east and north components of tidal velocity. (c) Tidal form factor, F  = (amp(ζ K1) + amp(ζ O1))/(amp(ζ M2) + amp(ζ S2)), where amp(ζ X) is the surface height amplitude of tidal constituent X . Small values of F indicate that tides are semidiurnal (two high and low waters per day); large values indicate tides are diurnal dominated, for example, in the Pacific sector along the Antarctic coast. Maps are on a Miller cylindrical projection to emphasize the polar regions.


 
Title: Re: Tides
Post by: johnm33 on August 10, 2020, 09:07:47 AM
Play the game not the man Binntho, now stop playing for time and back this up  "The physics of course is that the tidal effect is caused by expansion of water in the deep ocean at lower latitudes, with minimal actual movement of water except where coastal obstruction creates a local height/gravity imbalance (a fancy way of saying "downward slope")." 
or shut up.
Maybe i should take Mark Twains advice.
Title: Re: Tides
Post by: binntho on August 10, 2020, 09:20:59 AM
KiwiGriff posted three images above, and the first two are of particular interest - they show how very small and insignificant a factor the tides really are in the Arctic.

The first image shows the tidal effect - the Arctic is basically void of tidal effect compared with other oceans, the only one that gets near is the Mediterranean.

The second image shows tidal currents, and again the Arctic is basically a non-starter.

Now just to be clear, the following has already been established in eariler discussions and links to papers: There is a tidal effect in the Arctic. It is very small, perhaps 5 to 20 cm, and with a lateral fluctuation of perhaps 1km. Which is basically nothing. But in certain spots, the bathymetry combined with the very small tidal effect does increase turbulence enough so that warm waters do rise to the surface in these locations, and thus have an outsized effect on warming. Although this effect is apparently real, I've seen no quantification of it - so it could be totally insignificant in the larger scheme of things, or it could have a small but discernible effect on the total ice cover in the Arctic.

John's ideas have been about "tidal surges" and tidal currents somehow pushing their way through the Arctic, creating large and easily visible effects over large areas. Which is totally unfounded and not supported at all by any evidence.
Title: Re: Tides
Post by: oren on August 10, 2020, 09:26:09 AM
Binntho your last two posts were unhelpful. If you want to counter some of John's arguments please respond with focused questions/criticism/rebuttal of very specific points, not in generalities "oh dear John is lost" as these cannot convince anyone of anything and are frowned upon.
Also it seems to me that while you have raised some good points, you need to respond to John's counter of your own point about tidal expansion of water.

Edit: your previous two posts, this was typed while you made a new one.
Title: Re: Tides
Post by: binntho on August 10, 2020, 09:31:18 AM
Binntho your last two posts were unhelpful. If you want to counter some of John's arguments please respond with focused questions/criticism/rebuttal of very specific points, not in generalities "oh dear John is lost" as these cannot convince anyone of anything and are frowned upon.
Also it seems to me that while you have raised some good points, you need to respond to John's counter of your own point about tidal expansion of water.

Edit: your previous two posts, this was typed while you made a new one.

Oren, no. There should be no need or requirement to argue with someone who does not have the basic knowledge to understand the science behind his own claims or the counterarguments made by others.

John's total lack of knowledge exposes his own persona to attack. The claims he makes are so totally wrong and so totally lacking in supporting evidence that there is not point in arguing factually with him.

But still I have done so repeatedly, again and again, and it should not be my responsibility to keep pseudoscientific claptrap away from the main forums. That is why I have made the simple requirement that he be banned from posting to the main forum, and then he can pollute this thread to his own hearts content.
Title: Re: Tides
Post by: oren on August 10, 2020, 10:38:56 AM
No binntho, you have not been convincing enough for your requirement to be fulfilled. You have taken the original stance a long time ago that "tides do nothing" and are meaningless except maybe to slosh some water back and forth a bit, something which was obviously wrong even for the layman, and you only give way (and even that, barely) when presented with insurmountable evidence to the contrary. Thus you have been biased since the beginning, in my judgment. Admittedly, it appears to the layman's eyes that John's stance is that "tides do everything", which is also dubious at face value. However, to refute and rebutt you must delve down to very specific details. You have partially done that but then you resort to generalities again. That no one else has joined the debate on "your" side should give pause as well. I am willing to bet the truth is somewhere in the middle, but I lack the knowledge and even worse, the time, to delve into this issue and judge it by myself to my own satisfaction.
Title: Re: Tides
Post by: blumenkraft on August 10, 2020, 11:29:14 AM
Binnthos starting point was 'no vertical movement caused by tides'. Give him some time, he'll come around.
Title: Re: Tides
Post by: johnm33 on August 10, 2020, 11:38:13 AM
"tides do everything" no far from it my point is they are gradually doing more, and more, and that their effects, mainly in forcing currents, are becoming increasingly visible, i was genuinely worried i was stating the obvious, clearly not, but if you review my posts and not the cartoonish caricatures of them that should be clear. Whatever you see that cannot be explained by the weather can be explained by whats happening in the awakening ocean, and sometimes the ocean provides a simpler explanation for those things assigned to the weather.
You used the ratchet analogy where i use the flywheel, the flywheel being the currents the tides giving them a gentle push, and depending on the atmospheric set up different currents get that gentle push. For instance on the 26th i predicted/guessed that the forcing would be along the northern shelf of Greenland and clear the shelf, then the atmospherics changed and the incoming was redirected but not altogether and a limited but increased flow of incoming Atl. waters continues, imho, to skirt the shelf of the CAA and begins to penetrate the channels.
 Your call Oren I can continue with my own efforts to understand/make a fool of myself in public or private, because it may not look like it but I'm trying to find out why I'm wrong, so far without success and if even the rational don't 'get' what i'm saying then i question it's value.
Title: Re: Tides
Post by: oren on August 10, 2020, 11:51:02 AM
Please do continue in public John. This is an important issue and deserves research and discussion. Lacking the time and the background, how will I ever get to a semblance of knowledge without the efforts of others on this forum? I greatly appreciate your points even though I often have trouble understanding or corroborating them.
To be clear binntho, please continue as well, but discuss the subject. More details, less name calling please. Atrack each specific point as you see fit, leaving biases aside.
Title: Re: Tides
Post by: P-maker on August 10, 2020, 12:51:44 PM
Oren and bk,

This is both a matter of scale and and of change.

Some months ago we had a similar disagreement related to geothermal heat gradients in NE Greenland. This "constant" turned ot to have a miniscule impact on glacier melting in Greenland.

Now, we are discussing another "constant" - the tides in the Arctic Ocean. Binntho argues that it has a minuscule impact on the sea ice changes in the Arctic Ocean, which I tend to agree with.

Instead of putting Binntho into the "defence corner", it would be more convincing to ask others to provide some solid evidence, why the tides should have changed recently, and how these changes could have possibly affected the Arctic Sea extent.
Title: Re: Tides
Post by: Mark Tough on August 10, 2020, 01:27:04 PM
Just about to post something similar and as a very long lurker - I don't post that often.

A few points hopefully balanced  :)

- Unless the moon starts a slow drift to or from our earth, tides are a known constant
- Apogee and Perigee are two of my favourite words, so we know tides have extreme variants in a year, although known ones
- Extreme Low tides are ice tongue killers and that's when massive glaciers lose their support
-I expect that's when fast ice is also more likely to fail (sorry no citation) but again it's a known constant
-binntho - appreciate your steely gaze and as steely protection of the forum and the main threads from deniers and shall we say pseudo scientific word bloat - keep it real
-johnm33 - you are not that, your posts are valid
-Tides - Every 6 hours and 25 minutes there is a low or high tide that will break things, but again we know that.

Off Topic, I live in Maroubra, Sydney - fortunately near the beech. In Covid times it has been wonderful taking a walk on the headlands or a run on the beach where I live. Never in all my days here have I seen bigger surf and Winter Storms (4 to date) massive oceans and I go and watch in awe at high tide - tides matter and they devastate but we know where the moon is, it hasn't gone from 250 to 410 PPM Carbon, now that I'd say is a factor  :D

 
Title: Re: Tides
Post by: binntho on August 10, 2020, 01:43:06 PM
Oren and blumenkraft, this is simply a question of scale and perception.

My stance has always been, from the very start, that tides are almost exclusively a vertical movement with a small lateral factor mostly in coastal waters. I started posting on this subject as a response to a user that seemed to think that the tides caused a MASSIVE lateral movement of water. I can't remember if it was Johnm at the time, but it was e.g. the claim that there was a "tidal surge" into the Artic! Other of his postings have been along the same lines, he seems to think that the tides move SIGNIFICANT amounts of water laterally.

That is simply wrong. There is a very small and generally totally insignificant lateral movement out in the open ocean. But some people think that what they experience along the coast is what happens out in the open ocean. And this is wrong. It has always been wrong. It does not become less wrong by people showing anectdotal evidence of lateral movement along coasts and in narrow sounds and straits. It does not become less wrong by people describing how the tidal movement can cause localized turbulence where bathymetry allows, with surprisingly large knock-on effects.

The main point is: Tides are almost exclusively a vertical movement.

In the context of the first postings, I stated this more categorically - the tides are exclusively a vertical movement. This is true both when we think about the tidal pull as of itself, and also when we consider that probably 99.9% or more of the measurable movement is vertical. The lateral component is a miniscule part of the whole.

The reason I was so categorical was that the poster I was rebutting seemed to think that there was a largescale lateral movement pushing significant amounts of water around. Which is of course wrong.
Title: Re: Tides
Post by: johnm33 on August 10, 2020, 02:05:50 PM
" why the tides should have changed recently," I recall mentioning this a few times but since the ice has been cleared from the Barents sea they no longer inhibit tidal ingress, thus more water has found it's way into the Arctic proper and more has been forced out as a consequence, so they're the flywheel, that consequential forcing needs to be measured by others since all i can do is look at the available models.
Iirc i was the first here to point out the coincidence of the ice edge and the Barents shelf, what i thought then was being caused by waves i now suspect is caused by vortices generated by currents moving along the shelf and when the tides run the vorticity of those currents increase, or at least that's what the models seem to depict. Thus the tidal action liberated by the loss of Barentz ice now acts to maintain that loss.
 I also suspect the tides have been changing since Lomonosov had an ice sheet resting on it and will continue to change until lake Elgygytgyn [?] has an equible climate.
Title: Re: Tides
Post by: binntho on August 10, 2020, 02:08:47 PM
Johnm points a finger at the main point a few posts back, he found the following statement that I made earlier,
Quote
"the physics of course is that the tidal effect is caused by expansion of water in the deep ocean at lower latitudes, with minimal actual movement of water except where coastal obstruction creates a local height/gravity imbalance (a fancy way of saying "downward slope")

He wants me to substantiate this, because if true, his whole understanding of tides collapses. But this is actually fairly obviously the case - the rise and fall of the oceans due to the gravitational pull of the Moon and the Sun is caused by an expansion and contraction of the watercolumn in the deep ocean.

The surface of the ocean moves up and down due to pressure. This is well established and a rule of thumb is that every 1hPa corresponds to 1cm over deep ocean. So a single point in mid ocean may rise or fall by several feet over the course of a few days. And similarly, the sea level under a rapidly moving cyclone is significantly higher than in surrounding areas.

This pressure-induced movement is almost exclusively vertical. A rapidly moving low pressure area does not pull several km3 of sea water along (half a meter times 100km square is 5 km3 or 5000 million tons). The underlying watercolumn expands and contracts due to changes in the density of water. The mass does not change, but the volume does. See here for the relationship between pressure and density of water (https://www.engineeringtoolbox.com/fluid-density-temperature-pressure-d_309.html).

Pressure is a direct result of gravity, as is "slope" or "up" and "down". A ship sailing north from the equator is not going "down" even if, due to the shape of our planet, it is moving closer to the center of the Earth the further north it goes. The surface of the ocean follows a surface of equal gravitational pull, where the gravity of Earth and other plantes in competition with the centrifugal forces of the spin of the planet, creates a shape that contains the total mass of our planet.

The diurnal tidal fluctuation of the center of gravity creates the tides. When the center is closer to the Pacific, to take an example, it has the same effect as a fall in pressure - both water and air expands. The atmosphere is at more or less the same thickness around the globe and thus experiences an even up-and-down tidal movement in an eastward propagating wave.

But the oceans are vastly different, going from an average deep-sea depth of some 4000 meters down to nothing over the continents. The bulge of expansion wants to move towards the east, but the continents are in the way. This leads a much more complicated distribution of the tidal effect than would otherwise be the case, but the basic tenet still holds: Tidal movement is vertical expansion of water.
Title: Re: Tides
Post by: uniquorn on August 10, 2020, 07:52:17 PM
surely there is a paper on this somewhere

Some insignificant lateral movement 280km from the nearest coast  ;)
more details here (https://forum.arctic-sea-ice.net/index.php/topic,2417.msg280132.html#msg280132)
Title: Re: Tides
Post by: uniquorn on August 10, 2020, 08:09:14 PM
mosaic buoys in the fram strait. Are people really suggesting that continuous rotational movement doesn't affect melt? Please read upthread for further examples.
Title: Re: Tides
Post by: oren on August 11, 2020, 02:33:45 PM
this is actually fairly obviously the case - the rise and fall of the oceans due to the gravitational pull of the Moon and the Sun is caused by an expansion and contraction of the watercolumn in the deep ocean.

The diurnal tidal fluctuation of the center of gravity creates the tides. When the center is closer to the Pacific, to take an example, it has the same effect as a fall in pressure - both water and air expands. The atmosphere is at more or less the same thickness around the globe and thus experiences an even up-and-down tidal movement in an eastward propagating wave.

the basic tenet still holds: Tidal movement is vertical expansion of water.
I am sorry binntho, but all sources I have read point to these statements being fully in the wrong. The solid Earth and the water and air column do expand and contract slightly due the gravitational effects of the moon (and/or sun), but these do not cause the main effect of the tides. It is rather the lateral movement of water - due to the tangential forces - that causes the main effect of the tides.
These are not necessarily strong currents, and need quantification to support various claims on the effects of tides. But the qualitative explanation you provide is simply wrong.

I found this text to be more comprehensive than most.
https://www.lockhaven.edu/~dsimanek/scenario/tides.htm (https://www.lockhaven.edu/~dsimanek/scenario/tides.htm)
Quote
The moon's gravitational force acts in two ways on the earth:
* It stretches solid objects—an effect proportional to the inverse cube of the distance from the moon. This effect is simply too small to account for the tidal bulges in ocean water.
* The tangential components (tangent to earth's surface) exert tractive forces on large bodies of water directed toward the tidal bulges. These are also proportional to the inverse cube of distance from the moon. This is the dominant reason for tides in large bodies of water.

There are other sources which say the same things but less clearly.
Wikipedia says the same by the way.
Quote
Equilibrium
The equilibrium tide is the idealized tide assuming a landless Earth. It would produce a tidal bulge in the ocean, with the shape of an ellipsoid elongated towards the attracting body (Moon or Sun). It is not caused by the vertical pull nearest or farthest from the body, which is very weak; rather, it is caused by the tangent or "tractive" tidal force, which is strongest at about 45 degrees from the body, resulting in a horizontal tidal current.

But if you want to go on with the claim of vertical expansion only (which I am 100% convinced is wrong), please provide solid and clear supporting sources.
Title: Re: Tides
Post by: johnm33 on August 11, 2020, 09:34:29 PM
Great find Oren, the best single read on tides i've seen, the only two things he didn't address that came up for me in my thinking on the subject was that the moon doesn't really orbit the Earth but they circle one another in a kind of flattened helix, and although the oceans tides cannot circle the planet i wondered, if there was a solid core surrounded by liquid heavy metals whether they were free to 'slosh around' contiually and if so which would remain nearer the moon? but that's ot here.
I'll have to re-read the centrifugal/centripetal section because i had come to the veiw that these were intrinsic, if you will, to the gyroscopic motion of the atoms, and in this way the force acting on a molecule sprang from within in reaction to changing circumstance/position.
Title: Re: Tides
Post by: binntho on August 12, 2020, 07:03:00 AM
Oren, the document you linked to above seems very good and perhaps I have to reconsider. First i was interested in what he means by tractive so I'll include the definition from the article:

Quote
Tidal forces have radial components and tractive (tangent to the earth's surface) components. The radial components stretch or compress solid materials radially. The tractive components stress solid materials laterally, and, in the case of liquid materials, can physicaly move them significanty.

He then goes on to claim that

Quote
Water is very nearly incompressible and is clearly not rigid. So the tidal bulges in water arise because some water has moved toward the bulges from elsewhere, that is, from other regions of the ocean.

It is the claim that water is nearly incompressible that is obviously inconsistant with what I am saying. And it seems I have to retreat from my position - one of those scenarios where what you are absolutely certain you think is right turns out to be wrong. Which is why I'm an atheist!

To further hammer the point home, I found a peer-reviewed paper that explains the tides in much the same way as the author of the article you linked to, Tides and Water Levels (https://onlinelibrary.wiley.com/doi/full/10.1002/9781118476406.emoe122)

So it turns out that it is the lateral force that causes the tidal bulge, and in my enthusiasm in battling against the pseudoscience of Johnm and others I have myself gone down the wrong path.

So let's backtrack a bit: The main misconception of tides that I have been arguing against is that the tides somehow move vast amounts of water OTHER THAN the daily back-and-forth fluctuation.

Perhaps it is important to seperate this into two phenomena: The pulling of waters into a tidal bulge on the one hand, which I'll concede is what happens, and the tidal bulge pulling waters with it as it moves.

The first point, i.e. the pull and release of waters into the bulge, is simply a back-and- forth movement that doesn't really do anything. The second point is an absolute precondition for the claims of Johnm and others.
Title: Re: Tides
Post by: binntho on August 12, 2020, 07:21:05 AM
To clarify my position (which does not really change all that much even if my understanding of the basic forces behind the tides was wrong):

1. Tides do cause a back-and-forth movement. I think I've said this so often, so very many times, but it is important: It is a back AND forth movement. First one way, then the other. If it goes one way, it has to go the other way.

2. Tidal currents only exist where coasts or bathymetry interfere with the movement of the "bulge". And importantly, these currents go back and forth - if it moves water one way, it also moves water the other way.

3. The lateral movement of the tidal bulge does not pull water with it. The bulge rises and falls, it propagates as a wave and like all waves, it does not move water along with it.

A global estimate of the amount of water that gets pulled into the tidal bulge is some 150.000 km3, based on the areas of the oceans excluding the Arctic and the Mediterranean (where the tidal effect is minimal) and assuming an average of 50cm between high and low tide.

So every day, the tides move 150.000 km3 of water into each of the two tidal bulges. In comparison, the Gulf stream moves 13.000 km3 of water daily past Newfoundland. These numbers should demonstrate to anyone that even if the tides are moving large amounts of water back and forth, the water, on average and from day to day, STAYS IN PLACE.

If further evidence is needed, just look at the global ocean currents. They do not follow the movement of the tidal bulge. It may appear that they do in the North Atlantic, but if you look at the Pacific then it becomes obvious that ocean currents are not affected by the tides.
Title: Re: Tides
Post by: binntho on August 12, 2020, 07:37:18 AM
So why do I keep hammering at this? My first posting was as a response to someone claiming that there was a "tidal surge" into the Arctic.

This second batch of postings was in a response to postings from Johnm which blamed tides on everything, but specifically the claim that the tides were somehow forcing large amounts of Atlantic waters all around the Arctic (including the ESS and Beufort), pushing large amounts of Atlantic waters into and through all parts of the Arctic, forcing turbulence and what not everywhere he looked.

All of these claims are based on thinking that the movement of the tidal bulge equates lateral movement of vast amonuts of waters. Which is where I started - by saying that the tides are an up-and-down movement, not a lateral movement.

And the actual lateral movement is back-and-forth, not the one-way forcings that Johnm sees. And perhaps he is realising that he cannot use the tides to support his claims - I guess we are all learning something from this!

I refer specifically to the following posting from yesterday:

Looking at Mercator (http://bulletin.mercator-ocean.fr/en/permalink/PSY4/animation/3/20200801/20200806/2/2) salinity 30m it seems the Atl. waters are short circuiting and returning along Lomonosov from Laptev, they appear to be mixing with returns from ESS creating turbulence immediately beneath the openings in the ice north of Greenland.  I also suspect overflow from the Canadian side, by Belov trough, is forcing internal waves and actual movement in the basal layers towards Fram.
Strange that it [Atl.] doesn't get mixed maybe there's a wall of inert water holding station along the American side?

Are Atlantic waters "returning" from the Laptev, along the Lomonosov ridge, all the way to the north of Greenland along with "returns" from the ESS? What mysterious forces are at work here, cutting accross the entire Arctic ocean, with no regard for the halocline, thermocline or the currents that actually do exist? At least it's no longer the tides that are causing these vast currents that Johnm thinks he is seeing everywhere.

But his abuse of the tides, and the general lack of understanding of the tides that has lead to the amazing acquiescence of many members towards Johnm's postings seem to lead to others thinking that the tides somehow are a major force that can be used to explain all sorts of things. For example this from a poster from yesterday:

Quote
Wonder if it's due to ice thickness, perhaps due to the higher tide cycle,

The main point here is that the tides do not have any significant effect on anything. Which is not to say that they do not have some effect. They do, they exist and they cause some slight lateral movement, and some localized turbulence. But in the larger scale of things, they are simply not important.

Anybody with experience of sailing on the open oceans knows this: The tides are simply not important, they have no real effect on anything, unless in coastal waters.
Title: Re: Tides
Post by: interstitial on August 12, 2020, 09:11:03 AM
I think many times people assume that when someone stops arguing a point they are conceding the point. I don't think anyone should make that assumption. Especially with the number of trolls we seem to get on this site. (I don't have much experience on other forums so I have no real basis for comparison). There are many reasons not to respond.  I am beginning to realize life is too short to respond to those who are more interested in arguing than getting to the truth. I enjoy learning through discussion. In most circles consensus is often reached when those who know better stop arguing with  those who won't listen. That is why IMO group think tends to be so ridiculous.  Thankfully in science experiments lead to winners and losers in the long term and not stubbornness.  Unfortunately I get the impression that on this forum as on most of the Internet stubbornness reigns supreme.
Title: Re: Tides
Post by: oren on August 12, 2020, 10:54:58 AM
Quote
To clarify my position (which does not really change all that much even if my understanding of the basic forces behind the tides was wrong)
Binntho, it appears that at first you concede that the solid basis of your claims was wrong all along, and then you return to the same claims along with the accusation of pseudoscience. Just like the tides, the concepts moved back and forth and stayed in the same place.

However, now that you finally concede the main point - that tides do move large amounts of water laterally - I believe in your zeal you have not stopped to consider the implications.
It's true that tides move water back and forth, as the bulge does not stay in the same place. It's also true that it's not the same water that orbits the Earth along with the bulge, so it has some similarities to a wave. However for 6 hours water does move laterally, and a large amount of it. Now ask yourself:
A. What happens when the transported water has different properties than the water in the location it arrives to? E.g. Temperature, salinity, chemical signature.
B. What happens when that water gets deflected to the side by land or shallow bathymetry?
C. What happens when the water is transported north or south?
(All of these are various conceptual examples of ratcheting, converting a cyclical phenomenon into a unidirectional phenomenon).

The answer in all cases is that the incoming water gets mixed with the resident water, and 6 hours later when the reverse transport occurs it is slightly different water that comes back.
In case B a current or gyre may develop. The tide moves the water onto a diagonal feature, and the water is shifted sideways. When the reverse tide happens, the water transported back could be different water.
In case C the water being transported north is shifted east by the Coriolis effect. When the reverse tide occurs, the water being transported south is shifted west.
Now imagine you are in the Arctic, the coldest and freshest water in the NH. Any incoming water will almost by definition be warmer and more saline than the resident water. In addition incoming water will by definition be moving north and thus be pushed east, inducing a current inside the Arctic basin. Recall that the Arctic Ocean does not have many openings to the south, so a narrow opening will emit an eastbound tidal current that cannot be pulled back completely during outflow, as the water was already deflected beyond the opening. Bottom line, the tides do bring energy into the Arctic. How much? No clue. Negligible? I doubt it.

Lest we forget, tides may also cause fast ice to break - they lift it physically, thus possibly inducing its detachment from its anchoring points, and in addition may twist it laterally, if different tide heights are induced in sufficiently close locations. Of course all this applies only to coastal regions, but that is where fast ice is to be found. Fast ice is much more resilient to melting and export than mobile ice, thus higher tides may be somewhat detrimental to ice survival.

Of course these are just intuitive ramblings. I am no expert on tides. Neither are you, is what I finally realized.

While reading a bit more on tides, I asked myself whether tides have a significant north-south component. Had the moon been orbiting the Equator, no such component would have occurred. It turns out the moon's orbit is inclined by 18-28 degrees from the plane of the Equator, with an 18 year cycle. 2015 saw the minimal inclination, and 2024 will see the maximal inclination. Thus a north-south component does exist. I am sure people who know something about tides know all this.
And here's a little diagram that shows tidal amplitudes in the Arctic Basin, from an interesting paper about "Tidal currents in the western Svalbard Fjords". (Yes, they do exist).
Remember tidal range is double the tidal amplitude.
https://www.sciencedirect.com/science/article/pii/S0078323415000883 (https://www.sciencedirect.com/science/article/pii/S0078323415000883)

(https://ars.els-cdn.com/content/image/1-s2.0-S0078323415000883-gr2.jpg)
Title: Re: Tides
Post by: binntho on August 12, 2020, 11:50:50 AM
Oren, yes I do continue because the main point I have been trying to make doesn't seem to get accross.

Quote
What happens when the transported water has different properties than the water in the location it arrives to?
...
What happens when the water is transported north or south?

There is no "transported water" in the open ocean. That's the whole point. The "bulge" attracts water to itself laterally (as I have conceded). But the bulge does not move any water as it itself moves, as you have yourself just agreed.

And as I have repeatedly said, from the very beginning, bathymetry and coastal contours are different from the open ocean. There is transport of water in the Nares strait - first one way, then the other. It's tiny compared to the whole oft he Arctic and has no large-scale effect. There is turbulence in some specific bathymetric settings and this has some mixing effect, but not really quantified and unlikely to matter at all in the larger context.

Quote
The answer in all cases is that the incoming water gets mixed with the resident water, and 6 hours later when the reverse transport occurs it is slightly different water that comes back.

Only in the extremely tiny and dispersed cases of coastal tidal currents - of which the Nares current and it's extension to the north-east along the coast of Greenland is the only one!

Quote
Of course these are just intuitive ramblings. I am no expert on tides. Neither are you, is what I finally realized.

I never claimed to be an expert on tides, and you never thought I was (or you would never have argued with me!). On the contrary, I find them complicated and confusing, but I do know that they are not important in the large scale of things, and they do not really have any effect in the open ocean.

You see, if tides were that important, the scientific literature would be full of it. But it isn't. It's really extremely difficult to find any scientific papers about the Arctic that have anything to say about tides, and I've previously linked to scientific papers that would have mentioned tides if they were important, but they didn't, so they aren't.

And the main point all the time has been that some people seem to think that the tides move, or "transport", vast amounts of water laterally and can force them into the Arctic. Which is wrong.
Title: Re: Tides
Post by: JayW on August 12, 2020, 12:06:56 PM
Regarding the Yermak plateau
Quote
Turbulent mixing near the Yermak Plateau during the Coordinated Eastern Arctic Experiment
Abstract
Recent current measurements obtained from drifting platforms over the Yermak Plateau in the eastern Arctic Ocean confirm that the plateau is a region of greatly enhanced diurnal tidal currents. Modulation of the diurnal currents is clearly related to the plateau topography, as has been previously proposed. We show, however, that temporal variability due to spring‐neap modulation must also be considered in interpreting records from drifting platforms. We review simple models of tidal current amplification in this region and find that the previous assumption of near‐resonant, barotropic shelf waves propagating around the plateau's entire perimeter is inconsistent with the true topography. Instead, we propose that the diurnal variability is due to topographic shelf waves at the K 1 and O 1 tidal frequencies that are generated at points on the plateau's perimeter where the waves' group velocities are near zero. Observed cross‐slope variations in ellipticity, orientation, and magnitude of tidal oscillations are consistent with the presence of topographic waves generated in this manner. The topographic enhancement of the diurnal tide near the Yermak Plateau has important consequences for the sea ice cover, hydrography, and general circulation of this region. For example, the stress divergence applied by the tidal currents at the ice base greatly exceeds the typical divergence of the surface wind stress, and tides may therefore be important to local ice deformation. The strong cross‐slope tidal currents also appear to be responsible for the production of high‐frequency internal wave packets, which are associated with energetic diapycnal mixing in the pycnocline. We also consider the possibility that tidal rectification is responsible for a mean current transporting Atlantic Water clockwise around the plateau.
https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/92JC01097

Quote
Effects of tides on the quasi-steady upwelling-downwelling regimes and water mass exchange between the Arctic and Atlantic Oceans.
Abstract
Astronomical tides are strong in the regions of the Arctic shelf and GIN Seas, with amplitudes reaching up to 4.4m in the Hudson Strait, 2-3m in the White Sea and greater than 1m in the Canadian Archipelago. If nonlinear friction is present, at the sea bed or within a stratification water column, periodical motions transfer energy to shear stresses with a substantial non-periodic component. Over bottom topography, anomalous bottom shear stress generates vorticity and vertical motions, resulting in either an ageostrophic circulation or geostrophic upwelling/downwelling of isopycnals. Using a pan-Arctic and a North Atlantic ocean-ice model, both of which explicitly resolve tides, we examine the effects of tides on the vertical motions generated by Ekman pumping near the sea bed and at the ice-ocean interface, and the stretching and tilting of vorticity. We found that tides significantly increase the intensity of vertical upwellings and downwelling regimes near the shelf break. We extend the semi-geostrophic two dimensional Eliassen -Sawyer equation and three-dimensional omega-equation to take into account the effects of tides. We also discuss the application of the equations for the analysis of watermass transformations and dense water overflow in the main gateways between the Atlantic and Arctic Oceans : Fram Strait, Yermak Plateau, Barents Sea shelf break, Denmark Strait and Faroe Channel.

https://ui.adsabs.harvard.edu/abs/2016EGUGA..18.6301L/abstract
Title: Re: Tides
Post by: binntho on August 12, 2020, 12:56:51 PM
JayW, a couple of interesting papers, which don't really have a bearing on what I've been saying. Both of them are about effects outside of the Arctic Ocean proper, one being in the CAA and the other in the Kara between Yamal peninsula and Novaya Zemlya.

Both places have complex coastal contour and bathymetry, and both experience a tidal effect that is larger than in the Arctic Ocean. And neither paper claims a large effect from the tidal movements.

But of course, both of them are interesting and add to the general picture of the effects of tides in the Oceans in general and the Arctic in particular: Small and localized.
Title: Re: Tides
Post by: oren on August 12, 2020, 01:27:01 PM
Quote
There is no "transported water" in the open ocean. That's the whole point. The "bulge" attracts water to itself laterally (as I have conceded). But the bulge does not move any water as it itself moves, as you have yourself just agreed.
Binntho you again continue along this illogical path.
The bulge attracts water laterally, yet there is no transported water in the open ocean. How can this be I wonder?
Imagine a region in the Arctic ocean, north of Svalbard. At one time the water is lower by one meter or half meter compared to 6 hours later. Where did all this large volume of water come from? You bet, it came from elsewhere. Was it transported? What else would you call it? There is a net volume inflow into that region, and 6 hours later there is net volume outflow. No way around it I'm afraid,
Title: Re: Tides
Post by: uniquorn on August 12, 2020, 01:33:46 PM
Regarding the Yermak plateau
https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/92JC01097
Thank you JayW. A very interesting paper about a plateau north of Svalbard

(https://forum.arctic-sea-ice.net/index.php?action=dlattach;topic=3030.0;attach=280107;image)

In my humble opinion, ~7E to ~13E is significant. Then there is the shelf break all along the Nansen basin
Title: Re: Tides
Post by: blumenkraft on August 12, 2020, 02:50:12 PM
Regarding the Yermak plateau
Quote
... We review simple models of tidal current amplification in this region and find that the previous assumption of near‐resonant, barotropic shelf waves propagating around the plateau's entire perimeter is inconsistent with the true topography.

I remember overlaying the bathymetry on that movement some time ago. I thought i must have done it wrongly since the Plateau and the waves didn't match. The movement occurred a little further north. So this quoted part is especially interesting to me. Looks like this finding confirmes my overlay was correct after all.  8)

Also, check the upper right in the GIF above there seems to be a similar movement where the ice edge is at the moment. This is a little north to the southern elevation of the Yermak Plateau.

Binntho, if your 'in/out just the same thing' argument was true, you would see the same feature in the south of both points asynchronously. But there is no such movement there.
Title: Re: Tides
Post by: uniquorn on August 12, 2020, 02:59:00 PM
The turbulence appears north of the shelf. Depth rises from ~4000m to ~800m. We could do with a few more rammb's of that area to attempt to verify a daily event. Maybe in their own thread. There are currents here too, so tide will only be a contributary factor.

(https://forum.arctic-sea-ice.net/index.php?action=dlattach;topic=2417.0;attach=279902;image)

There aslo eddies west of the plateau and the molloy hole (https://en.wikipedia.org/wiki/Molloy_Deep), of course.
Title: Re: Tides
Post by: johnm33 on August 13, 2020, 03:11:01 PM
Bit of housekeeping, Gero. posted a link to this on the season page. https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2020GL089469
"Measurements of currents from a 15-year duration mooring record in the eastern Eurasian
Basin of the Arctic Ocean demonstrate that the previously identified weakening of
stratification in the halocline (e.g., Polyakov et al., 2017, 2018) has been accompanied by
increased upper-ocean current speeds and associated current shear. Most of this increased
energy and shear is in the semidiurnal band, which includes baroclinic tides and wind-driven
inertial oscillations, with little change of mean along-slope water transport (Pnyushkov et al.,
2018). "
Title: Re: Tides
Post by: blumenkraft on August 13, 2020, 03:31:36 PM
Here is a tidal swirl in the CAB. Somewhere a little east of the Lomonosov Ridge. The ocean is very deep here and the shores are far away!
Title: Re: Tides
Post by: uniquorn on August 13, 2020, 10:13:47 PM
Another couple of references

Baroclinic Tides: Theoretical Modeling and Observational Evidence
Vasiliy Vlasenko, Nataliya Stashchuk, Kolumban Hutter
Quote
This book was first published in 2005. When an oceanic tidal wave that is primarily active on the water surface passes an ocean shelf or a region with a seamount, it is split into a less energetic surface wave and other internal modes with different wavelengths and propagation speeds. This cascading process, from the barotropic tides to the baroclinic components, leads to the transformation of tidal energy into turbulence and heat, an important process for the dynamics of the lower ocean. Baroclinic Tides demonstrates the analytical and numerical methods used to study the generation and evolution of baroclinic tides and, by comparison with experiments and observational data, shows how to distinguish and interpret internal waves.


https://www.sciencedirect.com/science/article/abs/pii/S0079661197000281
Quote
Abstract

An approximate estimate of the energy in the first mode M2 baroclinic tide has been made from satellite observations. Results based on TOPEX/POSEIDON (T/P) precision altimetry indicate that the internal tide patterns are similar to those expected from mid-ocean topographic features in the global oceans. Both the orthotide and harmonic analyses indicate that the total energy in global M2 baroclinic tide is approximately 50 PJ. For a variety of reasons, M2 is the only component that can be obtained reliably from altimetric measurements. Even then, the energy value may be an underestimate and the energy flux, the dissipation rate, cannot be deduced from altimetry. Since it is the tidal currents flowing over mid-ocean topographic features that are responsible for generating internal tides, a model calibrated by M2 observations is a plausible alternative. Currents from a high resolution (
) barotropic tidal model have therefore been used to obtain an estimate of both the energy and the dissipation rate in M2, S2 and K1 baroclinic tides. A simple model of baroclinic tide generation has been used, and the unknown constant in this model has been selected to yield a total energy of 50 PJ in the first mode M2 baroclinic tide. Based on this calibration, the total energy is 8 PJ in S2 first mode baroclinic tide and 15 PJ in K1. The total in all first mode baroclinic tides is 90 PJ, about 16% of the total energy (580 PJ) in barotropic tides. The model results also suggest that about 360 GW of tidal energy are dissipated in M2 baroclinic tides alone, and 520 GW are dissipated in all first mode baroclinic tides. The latter value is approximately 15% of the power input into barotropic ocean tides (3490 GW) by the lunisolar tidal forces. We have preferred to be conservative and hence these are likely to be underestimates, especially since the altimetric tracks do not often intersect mid-ocean topographic features at optimum angles. While these values are very much within the range of earlier estimates in literature, they should be regarded as still uncertain to perhaps a factor of two (the dissipation rate could be anywhere from 400 GW to 800 GW, the most likely value being about 600 GW). The small signal to noise ratio involved in altimetric measurements of the surface manifestation of internal tides, and potential contamination by mesoscale signals are serious problems. In situ measurements at least a few locations underneath altimetric tracks are essential for confirmation and/or refinement of these preliminary estimates. Hopefully, these very first estimates of the energy and dissipation rate in global baroclinic tides, though rather crude, will serve as a catalyst for a better estimation in the future, since internal tides are likely to be a prominent source of mixing in the deep oceans and important to thermocline maintenance.

Quick bathy overlay using worldview, aug11   https://go.nasa.gov/30W1WR0
85.2N 157.4E  1100m drops to 3800m
(then back up to 2400m at 172.2E under the furthest east low conc area. Not sure if that is relevant)
Title: Re: Tides
Post by: uniquorn on August 14, 2020, 03:51:59 PM
https://twitter.com/seaice_de/status/1293073783830478848
Some interesting short videos on the thread, near FJL on the way to Polarstern
Title: Re: Tides
Post by: uniquorn on August 14, 2020, 05:02:03 PM
October 2, 2015
https://tos.org/oceanography/assets/docs/24-3_rainville.pdf
Quote
The Arctic Ocean traditionally has been described as an ocean with low variability and weak turbulence levels. Many years of observations from ice camps and ice-based instruments have shown that the sea ice cover effectively isolates the water column from direct wind forcing and damps existing motions, resulting in relatively small upper-ocean variability and an internal wave field that is much weaker than at lower latitudes. Under the ice, direct and indirect estimates across the Arctic basins suggest that turbulent mixing does not play a significant role in the general distribution of oceanic properties and the evolution of Arctic water masses. However, during ice-free periods, the wind generates inertial motions and internal waves, and contributes to deepening of the mixed layer both on the shelves and over the deep basins—as at lower latitudes. Through their associated vertical mixing, these motions can alter the distribution of properties in the water column. With an increasing fraction of the Arctic Ocean becoming ice-free in summer and in fall, there is a crucial need for a better understanding of the impact of direct wind forcing on the Arctic Ocean.

Title: Re: Tides
Post by: johnm33 on August 15, 2020, 12:16:45 AM
Looking at the 'Lomonosov eddy' it's difficult  to see what else could be causing that apart from basal movement. The simplest would be Atl.W. displacing water from the Wrangel abyssal plain, moving it towards the pole through perhaps both the narrower part of the Makarov basin and also Nemilov valley and since in both cases the water is moving directly towards the pole it has to shed angular momentum. I would expect such phenomenon to be short lived [if anything] simply because of the layers they have to penetrate but there are signs of them being there or thereabouts for days which may mean whatever real forcings are occuring they are in the first[?] stages of establishing a current, it is a natural path for a current to follow and probably the hardest part of overcoming the inertia of such a massive volume of water is creating the initial movement.
More widely the build up of the next tidal cycle has begun and I would expect an acceleration of Atl. waters moving north of Greenland to continue the damage being done there, we may also see waters forcing there way through to Baffin the morning of the 18th being the soonest and potentially the most game changing, especially if a surface current becomes established.
Title: Re: Tides
Post by: uniquorn on August 15, 2020, 12:14:33 PM
Lomonosov eddy - I see it as a more local volume event where 3800km3 tries to fit into 1100km3 twice a day (and back)
Title: Re: Tides
Post by: johnm33 on August 15, 2020, 06:49:31 PM
Something occured to me probably as a result of a comment by Oren, i know [something at least] about declination and perigee but somehow had never associated them with lateral movement. Thus I've persisted in an erroneus view[i think] about movement onto/into Barentz, that was that it was simply inertia [right/east] from movement north that forced the flow along to Kara but once lateral forces are taken into account the waters are delivered to the shelf just in time for the draw of the following tide to pull them eastwards, which may explain why mslp at the shelf is so important a factor. Nullschool (https://earth.nullschool.net/#current/wind/surface/level/overlay=mean_sea_level_pressure/orthographic=-316.19,81.36,298/loc=-75.000,-29.451)  click on 'projection' O added mp4 for the 18th best viewed slow.
Title: Re: Tides
Post by: blumenkraft on August 17, 2020, 11:36:06 AM
John, please drop me some thoughts of yours about a thing i think about these days.

From my observations, when the Lincoln Sea (and the CAA for that matter) is solidly frozen, you see a rather constent current down the Nares into the Baffin Bay. Sometimes so strong it breaks pieces from the arch (you can tell it's a current driven by water movement i e. more or less independent from wind direction). But when the Lincoln Sea ice is broken up and weak, there is no constant current. Ice movement is usually driven by wind and tides.

Why that difference? Is the solidly frozen sea ice in the north producing a pumping of sorts below it when the tides come in from the Atlantic? But that makes no sense since the ice is flexible, or is it?

Title: Re: Tides
Post by: blumenkraft on August 17, 2020, 11:46:48 AM
There is no need to drag your tidal fixation into it,

On the contrary, you cannot ever leave the tides out of sight, Binntho.
Title: Re: Tides
Post by: blumenkraft on August 17, 2020, 12:51:24 PM
No need to hesitate! Tidal motion is real, of course, and it's actually very interesting to see it in action. And the small back-and-forth fluctuation obviously has nothing to do with John's musings.

Binntho, do you think every tide is always the same? If not, what are the variables changing them?
Title: Re: Tides
Post by: johnm33 on August 17, 2020, 01:19:40 PM
"Why the difference?" The current varies a little with tidal pressure from the north but flows continuously at depth, because it's Atl. water it holds fast to the Greenland side and generates eddies wherever it 'snags' on that shore. In the winter without much to and fro above it those eddies reach the surface, once there's surface motion they get disrupted/masked by the more energetic turbulence of that. I think.
Title: Re: Tides
Post by: blumenkraft on August 17, 2020, 02:35:53 PM
Quote
flows continuously at depth

Oh, right. Thanks a lot, helps.
Title: Re: Tides
Post by: Tor Bejnar on August 17, 2020, 03:29:49 PM
Quote
because it's Atl. water it holds fast to the Greenland side
Within Nares Strait, the south-flowing water is on the Canadian side of the strait (and in the middle).  a small north-flowing current hugs the Greenland side.  (from the Icy Seas blog (https://icyseas.org/), a few years ago, I recall)
Title: Re: Tides
Post by: johnm33 on August 17, 2020, 06:19:21 PM
If you look on the same blog you'll find a post which describes a deep Atl. current turning left at Petermann and flowing upstream to cause melt at it's grounding line, iirc.
 Surface and near surface waters being 'native' to the Arctic do hug the Canadian side.
thought i'd check, not the post i recall but similar graphic https://icyseas.org/2017/06/16/is-petermann-gletscher-breaking-apart-this-summer/
Title: Re: Tides
Post by: uniquorn on August 23, 2020, 08:11:17 PM
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017GL075310
Quote
Plain Language Summary

The decline in aerial extent of sea ice covering the Arctic Ocean in the recent years is perhaps one of the leading indications of climate change. Warm water enters the Arctic Ocean at depths of 100–200 m; however, it is isolated from melting the ice by the lack of mixing in the Arctic Ocean. This lack of mixing has been attributed to the ocean being isolated from the wind by ice, and the fact that much of the Arctic Ocean is north of the critical latitude, beyond which the type of internal tide that is believed to drive mixing across other major oceans on the planet cannot occur. However, new evidence has been found that suggests that the tide might be important in driving mixing in certain areas of the Arctic Ocean. Here we combine state‐of‐the‐art numerical modeling with new turbulence measurements to identify the mechanism by which the tide can drive mixing at these high latitudes.

Quote
A map of the Arctic Ocean showing the position of the observations (yellow triangle). The critical latitude at which the local inertial period matches the period of the principle semidiurnal tidal constituent (M2) is shown as a red dashed line. Lighter blue areas indicate shallower regions including continental shelf seas and ridges, while the darker blue areas indicate abyssal depths. (b) The area of interest (the box outlined by a yellow dotted line in Figure 1a) showing contours of the rate of conversion of tidal energy (W m−2), in the M2 band, from the barotropic mode. (c) The Froude number distribution in the area of interest with bottom topography overlaid (black contours representing the 100, 200 and 300 m isobaths). (d) Mean profiles of buoyancy frequency (N2) and vertical shear in the current speed (S2) at the location of the observations. The mean is calculated for the 12 h period of the observations. The variability is shown by envelopes that represent the 95% confidence limits estimated by bootstrapping. These profiles indicate that the Gradient Richardson number over the thermocline region is close to one, and so the thermocline is of marginal stability.
Title: Re: Tides
Post by: gerontocrat on September 11, 2020, 06:29:35 PM
Rachel Carson, in her book "The Sea Around Us" - written in the late 1940's, spent some time discussing the work of Otto PETTERSON, who in 1913 published Climatic variations in historic and prehistoric time. in the UR Svenska Hydrografisk-Biologiska Kommisionens Skrifter.

Petterson incidentally was a colleague of one F. L. Ekman, the father of Vagn Walfrid Ekman, who gave his name to upwelling (Ekman suction) and downwelling (Ekman pumping).

Petterson researched for many years the phenomenon of submarine waves and the infuence of tides on them. He believed that variations in the strength of tides over long time periods has caused large changes in the climates of Greenland and Iceland and the extent of Arctic Sea Ice in the last 1,000 years or so, and that those variations are associated with variations in the orbits of the planets.

The field work he did over such a long period makes anything that the MOSAIC project has done look like peanuts. One might not accept his conclusions but cannot should not ignore the fieldwork and trawling through historical records that he did.

His paper is still accessible at http://www.mitosyfraudes.org/calen12/petterson_1.html

I wrote aboout it on "unsorted" in Dec 2018 and ended with..
Quote
Is it not possible that this science is still valid as a force that can enhance or reduce the effects of AGW? That mixing between that cold freshwater surface layer and deeper warmer, saltier water can be increased during periods of higher tidal action and reduced during periods of lower tidal action (by submarine waves)? And that in turn depends on variations in the orbits of the planets that are easily calculated using the mathematics of Newton?

https://forum.arctic-sea-ice.net/index.php/topic,2346.msg184103.html#msg184103

____________________________________________________
ps: The Severn Bore will be a 4 star event on 18th & 19th Sept just after the 17 Sept New Moon.




Title: Re: Tides
Post by: longwalks1 on September 13, 2020, 03:38:22 PM
Her book is available at Fadedpage.com

https://www.fadedpage.com/showbook.php?pid=20161022

Quote
Rachel Carson, author of Silent Spring, writes this book focusing on the plants and invertebrates surviving in the Atlantic zones between the lowest and the highest tides, between Newfoundland and the Florida keys. It's Appendix and Index make it a great reference tool for those interested in plant and animal life around tidepools
Title: Re: Tides
Post by: uniquorn on September 13, 2020, 04:04:08 PM
Some buoys near the pole