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Messages - binntho

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1
Arctic sea ice / Re: The 2020 melting season
« on: September 24, 2020, 06:42:39 AM »
I was talking about the minima, but doesn’t matter, it is a sterile discussion in any case.

I find interesting nonetheless how people get triggered with this.
...
little drop in the minimum since 2012, in fact, negative)

That's the way of the world, I fear: seemingly false claims do have the potential to "trigger" people.

This focus on the minima is a bit like somebody claiming that the world is not waming up because the temperature record of 1913 (56.7 C) has not yeat been matched.

The reality of course is different. And to repeat: Neither the data nor the physics support any claim about a stall in melt or ice reduction in the 2010s.

2
Arctic sea ice / Re: The 2020 melting season
« on: September 24, 2020, 06:33:07 AM »
After I wrote that message I realized that this would bring us back to our discussion at the start of the season; What adds more energy to system? Storms, or insolation? So it's good you wrote that.
...
It's all about adding energy to the system, and so we're back to our debate from old; What adds more energy to the system? A storm, or the sun?

I'm stubborn thinking it must be insolation, but I understand your argument now that storms add a lot of energy to the system as well. And storms do open up the ocean so that the heat from the sun can more easily be added to the system...

Indeed, it is a rehashing of an old haggis. And I seem to remember that both of us, and with Oren weighing in as well, came to the shared conclusion that insolation is the main cause of heat entering the system during peak insolation.

And we both agree that a storm causes mixing and thus brings heat from the ocean to bear on the ice.

But what seems to be missing from your reasoning is the fact that a typical storm is also a bringer and conveyor of warmth in and of itself. This is something that is obvious to those living in coastal areas in along the North Atlantic, Scotland, Iceland and Norway.

Outside of the short months of summer, a storm always has higher air temperatures than before or after. A typical late autumn or early spring storm in Iceland is easily 10 degrees centigrade, with heavy rain. I've even experienced storms like that in the middle of winter.  And there are periods where the storms come one after another, three or four in a week. And it is always colder between storms than during a storm except during high summer.

So back to the Arctic - I'd suggest that during June and July, storms would bring less energy to bear on the ice than insolation. During August, September and even further into the Autum, cyclones coming in from open water will transfer quite a lot of energy to the ice, while insolation is rapidly dropping down to nothing. During late spring, before insolation picks up, the same shold apply.

But we must not forget the third vector of energy infusion - ocean heat. And I would suggest that it is dwarves the others - but is at the same time inefficient in a melting contexts, since most of the heat does not reach the ice.

So can we rank these vectors and their interplay when it comes to melting ice? Even if Insolation would seem to be the favorite, we must remember that it still accounts for only around half the melt (simply because so much of a melting season happens outside of peak insolation).

Most of the rest I suppose is caused by ocean heat. And this is where storms kick in - they act both to give mechanical force to the system, mixing waters and moving the ice, and thus enabling the ocean heat to interact more efficiently with the ice. And secondly, the increased air temperatures and moisture that a storm carries in over the ice has it's origins in that same ocean heat.

So I'd suggest that insolation and ocean heat are the two main drivers of melt each year, with storms playing an important part in bringing the latter to bear on the ice, thus increasing melt at all times other than the during peak insolation.

And that storms can inhibit melt only during peak insolation, but will enhance melt during all other times.

3
Arctic sea ice / Re: The 2020 melting season
« on: September 23, 2020, 07:27:18 AM »
How is "melting" defined? When a storm destroys the ice, do we still call that melting? To me real melting means an input of energy into the system that raises the ocean temperature and makes the ice go away.

There is only melting ... it is a phase change of water and requires a hell of a lot of energy. Which means that if a storm causes melt, it must have brought energy to the ice, both by itself (storms in northern latitudes tend to have higher air temperatures than surrounding air masses, and more latent heat in the form of rain and humidity) and by causing pre-existing heat in the ocean to come into contact with the ice.

The oceans are getting warmer because of AGW, and this increase in global ocean temperatures is perhaps the main driver behind the steady decline of Arctic sea ice. The vagaries of weather cause annual fluctuation while the underlying near-linear trend is probably underpinned by increased global ocean temperatures. Since the rate of warming has been increasing, the rate of ice loss should presumably also be increasing, but I suspect that this change is happening too slowly to be apparent in our limited data series so far.

Local positive feedback is presumably also a contributing cause to the underlying trend. Increased ocean surface during melting season is a strong positive feedback that should be increasing the underlying rate of melt. Continental amplification during summer is probably also on the increase - the rate of summer warming in Siberia is significantly larger than global warming generally.

All of these factors should be causing an increase in the underlying rate of melt in the Arctic, and I suspect that this is what is really happening. The variations in weather and the annual swings arund the trend may be hiding this, and the increase in the rate of decline may well be too slow at this time to show up in our limited data sets.

But any talk of "slow down" is pure speculation, and not supported by the data nor by the physics of the system.

4
Arctic sea ice / Re: The 2020 melting season
« on: September 23, 2020, 07:09:07 AM »
As the NASA ice distribution shows, however, not much has changed in terms of multi year ice conditions since 2012. Ice extent has been around 4 mill. and the decline in volume and extent the 2010s has been notoriously reduced with respect to 2000s.

I would ask that you support these contentious claims with some proper analysis. I am unaware of there has been a reduction (notorious or otherwise) in the decline of volume and extent in the 2010s.

For extent, we can look at Gerontocrats 365 day average which clearly shows that the rate of decline is not slower in the 2010s than it was in the 20 year period before that. There are big swings, and the deep drop in 2008 stands out, but the general trend is clearly as close to a linear decline as makes no difference.



For volume, the graph below shows average monthly volume (from this excellent collection of graphs). Although a quick glance would seem to indicate changes in trend, particularly with the minima since 2010, the trendline (added by me, freehand) shows how unlikely it is that any putative slowdown were to be found to be statistically valid.

5
Arctic sea ice / Re: MOSAiC news
« on: September 22, 2020, 07:24:10 AM »
I think tides have a part to play in the arctic, more importantly at the shelf breaks.
I agree. But perhaps it is a part that is not easily visible to us.

Quote
Also shown is P163 drift speed. Calculating the time between 12 peaks in the centre gave an average of 23.29hrs/peak which is too short for a lunar cycle so I'm open to other explanations.

But fits well with an inertial oscillation (IO) at slightly less than 2 per day this close to the pole. From my reading I gather that the IO goes from 2/day at 90N to 0 at the equator.

Quote
Meanwhile here are some of the remaining Mosaic buoys in the Greenland Sea.
Not really possible to discern any tidal oscillation, perhaps the scale is too large. We know that there is a larger tidal effect here than in the Arctic, although not all that large (you need to go south of the Greenland-Iceland-Scotland line to get into proper tidal movement). The maximum tidal movement in Longyearbyen is around 2m, in Reykjavik it is almost 5m. Out in the open ocean, the movement is signifcantly less, perhaps 0.5m in the Greenland sea, 1 - 1.5m just south of Iceland.

6
Arctic sea ice / Re: MOSAiC news
« on: September 21, 2020, 03:42:26 PM »
I’d say there’s only one rotational mvmt of significance superposed to the green line,

Absolutely.

Quote
the red looks to me like a cycloid wrapped around. Is that the secondary oscillation that appears as the floe moves due to inertia-coriolis imbalance with 1/2 day period?
AKA inertial oscillation. This is exactly the question in my mind too - has uniqorn been showing us animations of tidal oscillation or inertial oscillation? And does that mean that there is no (or at the very most negligible) tidal movement in the Arctic?

7
Arctic sea ice / Re: MOSAiC news
« on: September 21, 2020, 12:19:07 PM »
The silly discussion above on what could be the cause of the circular movement of the buyo, i.e. the path shown in green below, has lead to a major discovery for me, and to a serious conundrum:

Are all of the "tidal movements" that uniqorn has been showing us in fact only "inertial oscillations"? Or only some of them? Which ones? How can we tell?

As A-Team has so boldly stated, tidal movement is negligible in the Arctic (or more precisely: Around Mosaic). Personally I have been of the same opinion regarding tides, but uniqorn did seem to have proved the opposite with his fantastic animations.

So what are we in fact looking at in all the wirls and curves around the green path line? Is it only the ice doing it's inertial oscillations on top of the ocean surface, is it the ocean itself inertially oscillating, is it the tidal pulse shifting waters back and forth or what?

I've made a very lukewarm search of tidal movements of Argo floats which would be incredibly interesting for comparison. Can tidal movement be seen at all in the drift of a typical Argo float in the North Atlantic (one of the strongest tidal areas) let alone in a near-todally-dead tidal zone such as the Mediterranean or the Arctic? What would the tidal signal look like in a buyo floating free of the ice pack?

All questions way above my pay grade.

8
Arctic sea ice / Re: MOSAiC news
« on: September 21, 2020, 11:45:57 AM »
It's time to thank you again uniquorn, for your immense analytic and graphical contribution on this thread and in many other threads. I am sure your time doesn't come free either. The output is much appreciated by me and by many other posters both silent and vocal, as well as by many lurkers I am sure.
Absolutely!

9
Arctic sea ice / Re: The 2020 melting season
« on: September 21, 2020, 08:12:27 AM »
Btw that thick looking bit north of svalbard is a stream of icebergs from Greenland.

No.

10
Arctic sea ice / Re: MOSAiC news
« on: September 20, 2020, 04:16:41 PM »
Amazing! I must admit that I have never heard of this inertial oscillation phenomenon. So no, I had not considered it ...

From the paper u300673 linked to above, and from A-Team's excellent post (as how could it not be) it seems that tidal oscillation and inertial oscillation have the same frequency and can easily be confused with each other.

Quote from: Sea ice inertial oscillations in the Arctic Basin
As the Arctic Basin lies between 70◦ and 90◦ of latitude, the inertial oscillation frequency varies from −1.88 to −2 cycles day−1 at these latitudes and is thus merged with the semi-diurnal tidal oscillation frequency. The differentiation of these two types of oscillations can be done by looking at the amplitude of the Fourier spectrum with respect to signed frequencies ...

So having considered inertial oscillation I find it easy to dismiss - it cannot explain the cyclical path of the buoy and so we are back to my first guess of changes in wind direction.

11
Arctic sea ice / Re: MOSAiC news
« on: September 20, 2020, 06:49:20 AM »

EDIT: The speed of drift swings between 10% and 20% of normal walking speed. And the tidal swings are only a few hundred meters each way. The circular movement I guess has more to do with changing wind direction than anything else.

Great. As you guessed that one hopefully you will run the numbers to prove it. Hourly wind direction from PS is here   P169 is near if you need buoy data.
I suspect it is the combination of both since wind drift appears to be of the same order of magnitude as 'tidal drift' and it's a more likely explanation than continuous tight wind vortexes at multiples of walking speed. 
A guess does not need proof. Circular motion needs explanation, and I'm at a loss to see what else it could be. Some sort of ocean current turbulence is of course also a possibility, but less likely to my mind.

The drift speed is not at "multiples of walking speed" in normal parlance. Slow strolling is 1m/s, while brisk walking is nearer to 1.5 m/s. The buyos drift speed swings around 0.1 m/s. I'm not sure what you mean by "tidal drift", I don't think such a thing exists. But the sideways pulsation of water every 6 hours sems to be in the region of a few hundred meters each way every 6 hours, translating into a slow pendulum swing at 0.02 m/s.

Uniqorn's animation (repeated below) does not indicate any wind vortexes at any speed. The twoo loops at the center of the image can be seen as a result of slow drift closely aligned to the direcion of the tidal pulse. If we were to remove the tidal factor, the buoy movement would paint a circle with a radius of 1 or 2 km over a three day period. Changes in wind direction seems the most likely explanation, but it is of course the surrounding ice that is moving and the forces causing the changes in movement could just as well be found hundreds of kms distant.


12
Arctic sea ice / Re: MOSAiC news
« on: September 19, 2020, 04:14:32 PM »
drift update from P176.
2 submarine landslides a day seems unlikely. I think I'll stick with tides.
Absolutely (grrmble grrmble) and the gif is fantastic, almost like a Micky Mouse picture. But as usual I miss scale from your gifs, and it is tedious to have to freeze two frames, read the coordinates and then calculate the distance to see that your gif is appr. 10 x 5 km square.

EDIT: The speed of drift swings between 10% and 20% of normal walking speed. And the tidal swings are only a few hundred meters each way. The circular movement I guess has more to do with changing wind direction than anything else.

13
Arctic sea ice / Re: MOSAiC news
« on: September 19, 2020, 04:09:06 PM »
Makes mostly sense to me,  a different style of writing, but then.. I am a smoker :)
I have been thinking about submarine landslides. Also to try to understand the north-east Greenland strangeness.

So "exponential runaway geothermal blowout" makes sense to you? OTG entire line of reasoning is from never-never land and does not apply to planet Earth. EDIT: In fact it's so totally off the grid that I suspect OTG is a nom-de-plume of someone making fun of us by threading pseudoscientific waffles on his hook and seeing how many bites he gets.

14
Arctic sea ice / Re: MOSAiC news
« on: September 19, 2020, 05:34:05 AM »
Also outburst flushing from Greenland, which looks to be going through exponential runaway geothermal blowout, has been launching submarine landslides that are shedding violent fresh upwellings ... and possibly mini tsunami surges, which could look like standard tidal effects, since the subglacial outbursts occur primarily at high tides.

What are you smoking?

15
Arctic sea ice / Re: Changing Arctic Ocean Currents
« on: September 18, 2020, 03:06:05 PM »
I agree with Hefaistos - the evidence is not conclusive. And as one of the commenters on Real Climate pointed out: Rahmsdorf forgot to post the graph showing the clever tidal gauge based reconstruction of the Florida current. So here it is below.

Altough it is true that there is a slight downward trend, and that 1909 was one of the peak years, probably in second place after 1932, what is sorely missing is any correlation with other events on our fair planet.

It is possible to discern a drop after the temperature peak at the middle of the century, but other than that there is no visible correlation with recent warming - in other words, the downwards trend is not speeding up.

Rather the oppisite, the last 30 years seem to show no trend or possibly a slight upwards trend. But without clear correlation with other planetary changes, nor any clear causal connection, a clear conclusion seems a distant dream.

16
Arctic sea ice / Re: Slater's thread
« on: September 17, 2020, 01:53:12 PM »
Thanks El Cid. I'll try to remember that til next time! But the "naive" forecast seems to have predicted the minimum pretty well, while Slater's predictions are off the mark by an unusual amount.

Which tells us ... about the Artic and the changes it is undergoing (fill in blank with your thoughts).

17
Arctic sea ice / Re: Slater's thread
« on: September 17, 2020, 10:17:50 AM »
The anomaly forecast (light blue line) is NOT the Slater forecast. It is simply there to show what a naive forecast approach would be, ie. looking at the current anomaly and saying that the size of the anomaly would stay the same in the future.
A bit clearer, but still more needed: How is the anomaly calculated (i.e. anomaly of what from what) and is "the future" the same 50 days as in the Slater forecast?

18
Arctic sea ice / Re: Slater's thread
« on: September 17, 2020, 09:46:39 AM »
Clearly by spot on I meant that their anomaly forecast for minimum was accurate. And there is ample discussion in this thread about what Anomaly forecast means, what the 50 day lead is, and the comparisons between the two.

Peruse at your pleasure.

So you mean an "explanation" like this one here:

What does anomaly forecast mean?

That if its 100k below the norm for the time of year now, it will be 100k below the norm for the time of year in future.

Which is not very helpful. But of course if nobody understands what Anomaly forecast is, then the lack of understandable explanations become clear. The Slater website makes no attempt at explanation.

As long as nobody can explain what the Anomaly line means, there is no way to claim that the Slater model has been anywhere near being able to make any real predictions this year.

Just look at the graph. The dark blue line jumps all over the place with very little correlation with the red line, predictive valu nil. The light blue line is practically never comes close to the red line except at the very end.  And since nobody knows what the blue line is showing, no conclusions can be drawn from it!

The Slater website has 2016 as "last year", shown below. That year the predictions were actually quite good, notice the close correlation between the red and dark blue lines towards main melting season, while the the light blue line stays well away from both.

19
Arctic sea ice / Re: Slater's thread
« on: September 17, 2020, 08:48:43 AM »
Anomaly forecast is spot on?
"Spot on" is apt - the red and the light-blue lines only touch that one time! Not a good match in my not so humble opinion.

Besides, what is meant by "Anomaly foreacast" ...

20
Arctic sea ice / Re: Slater's thread
« on: September 17, 2020, 06:31:15 AM »
To my eyes it seems to be wildly off ... so not sure what there is to credit.

21
Arctic sea ice / Re: Glossary ... for newbies and others
« on: September 16, 2020, 11:31:22 AM »

22
Arctic sea ice / Re: Changing Arctic Ocean Currents
« on: September 16, 2020, 11:09:13 AM »
thanks, i had never heard of it either. If I understood correctly, we are reinforcing the engine of the AMOC, and the power of its brake is questioned
perhaps we are strengthening the "Indian Ocean" engine so much that it compensates for the brake at Greenland (Greenlandic explanation seemed logical all the same, isn't it  ?)
There were several explanations for the "cold blob" or "warming hole" south of Greenland. One was that it was due to melt-water runoff from Greenland and a commonly stated effect was that it was somehow slowing down the AMOC in that area. This perhaps sounded logical but that doesn't make it right.

To begin with, meltwater runoff from Greenland is still nowhere near enough to cause any significant changes to the AMOC. Secondly, the "cold blob" is in an area where the water is heading down south again, and may well sink below a surface cooled by northerly winds. And the high SSTs both north and south of the blob indicates a vigorous heat transport.

A very recent article about this is Multiple drivers of the North Atlantic warming hole, from the Abstract it seems as if one of the explanation is increased heat transfer to the north of the area. Or in other words: The "cold blob" is cold because more of the heat is being transferred further north, and thus the waters returning south are colder than usual.




23
Arctic sea ice / Re: Glossary ... for newbies and others
« on: September 16, 2020, 07:28:56 AM »
BOE stands for "Blue Ocean Event", and the inclusion of the word "Event" indicates something that can neither be fractional nor partial nor continuous with previous or later states, nor can it really be defined as when some specific measure drops below some arbitrary line.

A proper use of the term BOE would indicated the first time all ice disappears. It cannot really be used to describe the first time ice goes under 1Mkm2 simply because the day that happens will be no different from the day before or the day after. Going under 1Mkm2 is an arbitrary point on a continuum, not an event in real-world terms.

Same goes for this strange use of the term "partial" or "fractional" BOE. There is no such thing as a partial event.

I'm not sure about the history of BOE as a concept, but I remember a few years back when a lot of people become excited about a hypothetical future BOE with several of them claiming that following BOE, ice would not regenerate and the Arctic would flip into a new regime, a tipping point of epic proportion. This line of argument is obviously using BOE to mean "when all ice disappears".

Further to the earlier discussions on BOE were claims that the world as we know it would end shortly afterwards - not only the Arctic but the entire planet would have reached a catastrophic tipping point. Again this line of discussion does not allow for a definition of BOE as meaning "going under 1Mkm2".

I remember reading for the first time some years ago the suggestion that BOE be re-defined as "virtually ice free", and to use the apparently widespread definition of under 1Mkm2 as the arbitry limit.  I didn't think much of it at the time.

Buit this confusion of terms is becoming increasingly unfortunate in my mind. People are really talking about VIF (virtually ice free) which is not an event. Thus using terms such as "partial VIF" is reasonable, while "partial BOE" is nonsense. This confusion of BOE with VIF also makes impossible all speculation and discussion of tipping points or sudden and epic systemic changes following BOE - which I don't really believe in, but other people do, and it would be silly for them to try and come up with new terms because some lazy scientists have stolen BOE - are we to start talking about TIFE (totally ice free event) instead?

BOE is an event, something that happens clearly and is easily definable and discernible, and defendable as well. Nobody is going to claim any major changes to the Arctic just because at some hypothetical point in the future, ice extent drops to the 990.000km2s for a few days. That would be laughable, and totally negate the whole idea behind the term BOE.

So i would suggest to stop using BOE as a tag for "virtually ice free". and start using VIF instead. And that the rest of us start to think about how to actually discern when this Event takes place, I personally like the idea of FMI 80N lift-off being the unmistakable sign of a BOE.

<Don't make it personal. O>

24
Arctic sea ice / Re: Changing Arctic Ocean Currents
« on: September 15, 2020, 11:13:00 AM »
I've never really been convinced that the AMOC was slowing or weakening. The system as a whole is very variable and changes cyclically, but the waters north of the GIS gap and south of Labrador have both been unusually warm for several years, indicating that the Greenland cold spot is an unrelated phenomena and that the conveyance of oceanic heat to the far north is continuing unabated.

The much hyped putative driver behind a percieved slow-down doesn't really exist in geologically modern times: No glacier is big enough, close enough, and melting fast enough, or draining suffiiciently into the Arctic to cause a fresh-water induced slowdown - which is a popular theory to explain big swings in the AMOC in the geological past.

And a quick google on "amoc strengthening" finds plenty of evidence to support Hefaistos' post, including this one in Science Direct from 2016: There is no real evidence for a diminishing trend of the Atlantic meridional overturning circulation

here is another interesting paper, On freshwater fluxes and the Atlantic meridional overturning circulation. From the Abstract:

Quote
While the role of freshwater forcing in the AMOC has received much attention, this question remains unresolved ... Our results robustly suggest that for the equilibrium state of the modern ocean, freshwater fluxes strengthen the AMOC

Recent research is pointing to a link between the Indian Ocean and the AMOC, with a warmer
IO causing a stronger AMOC. There are plenty of papers to be found online, including this one:

PC23A-03 - The Strengthening of the Atlantic Ocean Meridional Overturning Circulation Caused by Enhanced Indian Ocean Warming, from the Abstract:

Quote
Here, we describe how a salient feature of anthropogenic climate change – enhanced warming of the tropical Indian ocean (TIO) – can strengthen the Atlantic meridional overturning circulation (AMOC) by modulating salinity distribution in the Atlantic

25
Arctic sea ice / Re: What's new in the Arctic ?
« on: September 14, 2020, 11:25:37 AM »
Climate change: Warmth shatters section of Greenland ice shelf

The "Spalte" tongue of the Seventyninefjord (Nioghalvfjerdsfjorden) glacier has disintegrated:

Quote
Nioghalvfjerdsfjorden is roughly 80km long by 20km wide and is the floating front end of the Northeast Greenland Ice Stream - where it flows off the land into the ocean to become buoyant.

At its leading edge, the 79N glacier splits in two, with a minor offshoot turning directly north. It's this offshoot, or tributary, called Spalte Glacier, that has now disintegrated.

Some of us have a strange fixation (or aversion) to tides, so perhaps this article about the tidal movement of the 79N glacier is of some interest, Tidal movement of Nioghalvfjerdsfjorden glacier, northeast Greenland: observations and modelling

The tidal at the mouth of the fjord, at the comically named "Syge Moster" island (i.e. "Sick mothers sister's island"), was measured as being between 0.5 and 1 m each way.

26
Arctic sea ice / Re: The 2020 melting season
« on: September 11, 2020, 07:03:49 AM »
I'm starting to think that my confident prediction of a minimum in the second half of the 4th million is soon to be proven wrong. But then I'm getting used to being wrong about things, so chin up and stiff upper lip and all that!

But thinking back to all those who confidently dismissed any changes of 2nd place when melt slowed down in the beginning of August does help put the spring back into my step.

27
Arctic sea ice / Re: The 2020 melting season
« on: September 11, 2020, 05:44:58 AM »
I ask that you indulge my bathymetry-and-ice-distribution fixation one more time.

Whenever you want!

Looking at the gif, the correlation between bathymetry and the ice edge on the Atlantic front is very clear, with 2020 being the obvious outsider (there is little correlation elsewhere in the Arctic).

I think people mostly understand bathymetry in terms the various depths, and see the ice edge somehow following the contour of the edge of the Eurasian continental shelf. But there is another feature that follows this same edge, i.e. the islands separating the Atlantic and Barents seas from the Arctic.

Both features are bathymetric (i.e. the coastal lines of the islands, and the edge of the continental shelf) and both probably have an effect on the likely ice edge at minimum - it is not only the sudden depth but also the presence of these islands that effect the position of the ice edge at minimum.

28
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: September 09, 2020, 02:47:43 PM »
... I wish they had deployed a grid full of buoys to study what's happening between Greenland and the pole.
Second that!

29
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: September 09, 2020, 06:48:14 AM »
It seems that this whole tidal turbulence and upwelling aspect of Arctic waters is a ripe field for investigation. I agree with uniqorn, and I think I mentioned this before, but these turbulences (wherever they may be found) could be on the brink of "punching through" the overlying ice in summer in various locations, possibly starting a cascading breakdown of the halocline and "oceanification" in the middle of the pack?

30
Arctic sea ice / Re: Melt Ponds
« on: September 05, 2020, 07:22:56 PM »
Indeed, one is suffused by a gratifying feeling of of being fully informed. Thanks.

31
Arctic sea ice / Re: The 2020 melting season
« on: September 05, 2020, 08:06:39 AM »
August 31 - September 4.

2019.
Atlantic side well past 85N, the Beaufort claw rapidly disappearing, and no visible signs of an end to the melting season.

32
Arctic sea ice / Re: MOSAiC news
« on: September 04, 2020, 01:05:12 PM »
And with some trepidation:

The tides and tidal currents at the current location are completely negligible.

but (red underline added) :
But that is exactly why A-Team gave an alternative explanation:
The tides and tidal currents at the current location are completely negligible. The issue for a solid week has been a strong persistent wind off Siberia that is quite noticeably moving the whole ice pack towards Banks Island. These winds can induce semi-diurnal near-inertial waves in the water that the public relations lady may be confusing with weak M2 lunar tides.
<>
Yes, I could deduce the same from A-Team's terse statements (and did in fact deduce the same) but just saying things doesn't make them true.<>

I for one am not really able to see how consistent wind can be confused with tidal movement.

<Removed antagonistic language. O>
You are going too far here Oren. What was so antagonistic other than that I dared to point a critical finger at A-Team?

I wrote a well considered and well written comment worth reading and sharing. If A-Team insists in making sweeping statements and not bothering to defend them, then I suggest that you start snipping him.

33
Arctic sea ice / Re: The 2020 melting season
« on: September 04, 2020, 01:02:51 PM »
Refreeze of water on top of the ice surface is what I meant, melt pond freeze, but for good until next year, is what I meant. Plus there are signs of ocean surface freezing in the ESS/Laptev tip of the pack, but I cannot be 100% sure.
The first measurable open water refreeze will happen no later than end of next next.

Good to clear that up. So perhaps you can explain what you meant originally,

This is a weird breakup. Can this be because of wave action?
BTW, This is no wave action, as before Aug 31 there was none in that area.
This polynya so visible is probably due to ice surface refrozen, and then broken by deformation of the pack, just as it happens in winter.

What causes the deformation, and what does (meltpond) surface refeeze have to do with a polynia several tens of kms wide?

34
Arctic sea ice / Re: Melt Ponds
« on: September 04, 2020, 11:14:07 AM »
Oren, acknowledged. And thanks for reminding me that when water from meltponds seeps into the underlying ice, it freezes and seals off the meltpond and increases the structural strength of the floe.

But this use of "drain" is not what the original poster (Glenn) had in mind.

So let's clarify that meltponds can indeed drain in the sense that "parts or all of the water moves down into the ice".

And of course, partial draining of a meltpond is also draining, and the sinking of surface water into porous ice could potentlially leave a "dry" meltpond with a bottom lower than the surrounding sea level.

But the thinking that meltponds can drain out through the bottom of the ice, even that they can somehow "punch" their way out, is clearly wrong.

35
Arctic sea ice / Re: MOSAiC news
« on: September 04, 2020, 11:03:31 AM »
And with some trepidation:

The tides and tidal currents at the current location are completely negligible.

but (red underline added) :
But that is exactly why A-Team gave an alternative explanation:
The tides and tidal currents at the current location are completely negligible. The issue for a solid week has been a strong persistent wind off Siberia that is quite noticeably moving the whole ice pack towards Banks Island. These winds can induce semi-diurnal near-inertial waves in the water that the public relations lady may be confusing with weak M2 lunar tides.
<>
Yes, I could deduce the same from A-Team's terse statements (and did in fact deduce the same) but just saying things doesn't make them true.<>

I for one am not really able to see how consistent wind can be confused with tidal movement.

<Removed antagonistic language. O>

36
Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: September 04, 2020, 08:22:18 AM »
This is how they can perform feats like filling in a sinkhole and open up for traffic again in 3 hours. By closing everything down for three days for an electricity audit ...

37
Arctic sea ice / Re: MOSAiC news
« on: September 04, 2020, 07:02:44 AM »
And with some trepidation:

The tides and tidal currents at the current location are completely negligible.

but (red underline added) :

38
Arctic sea ice / Re: MOSAiC news
« on: September 04, 2020, 06:59:01 AM »
As was pointed out to me thickness is weighted by concentration so that should be factored in as well. Polersterns location does not appear to be at 100%.
Indeed. The claim that Hycom is "way off the mark" needs clarification. How long did it take them to find a floe thick enough for their needs? If the surrounding ice is made up of 1.5 meter thick large floes, how did Polarstern get there? I see nothing here that invalidates Hycom's estimate of 0,7m in this area.

39
Arctic sea ice / Re: The Arctic for Amateurs and Newbies
« on: September 04, 2020, 06:50:59 AM »
Blame the Norwegians! :)
NO!
But then you show an image that clearly demonstrates that the word came to English via the Norwegian "flo".

40
Arctic sea ice / Re: Melt Ponds
« on: September 04, 2020, 06:47:04 AM »
Fine to move the discussion here. But the discussion above is not the discussion I was having.

My point was about the verb "to drain" and my claim that a meltpond on floating ice cannot "drain" under realistic circumstances. But to recap, this discussion started when Glenn_Tamblyn posted this a few days back:

However, if a melt pond drains, could that trigger other issues. A while back scientists identified a mechanism they think is involved in the collapse of large ice shelves. Obviously they are fresh water ice and a couple of orders of magnitude thicker but might the same mechanism apply to sea ice?

- Melt pond forms, down to some depth.
- Melt pond drains away.
- The ice beneath the melt pond now needs to rise to rebalance buoyancy.
- But the ice surrounding the drained pond doesn't need to adjust.
- Thus leading to stresses in the ice around the edges of the empty pond as the empty pond tries to rise, and potentially cracking.
- Repeated occurrences of this is believed to lead to a cascading failure and collapse of ice shelves.

But mdoloner stated the obvious:

Melt ponds cannot drain. nine tenths of the floe is below sea level.

And I honestly thought that that was that. I'ts all about the word "drain" which implies that water disappears down an opening and flows away. The big meltponds on top of glaciers do exactly this.

But a water on top of a floating floe cannot "drain". If a crack were to appear, water would enter from below at the same time as the level of the meltpond would sink to meet the water level surrounding the floe. This is not "draining" unless the bottom of the meltpond is higher than the surrounding sea level.

Shared humanity weighed in with:

??? Once melt water has punched through the ice floe, it will seek its own level which would be sea level.

which begs the question - what forces allow melt water to "punch through" an ice floe? This phrasing doesn't explain anything, neither as a mechanism nor as a metaphor.

Finally Glenn_Tamblin answers mdoliner with the following example:

Imagine a floe 2 meters thick, 20 cm above water level. A melt pond forms in the middle of it, 40 cm deep, but not in contact with the ocean below. Then cracking allows it to drain.

Which is what triggered my posting.

This whole discussion is about the difference between a rigid but floating ice shelf possibly hundreds of meters thick, where meltponds form on the surface and when cracking occurs, the water in the meltpond obviously drains away (it flows down into the crack to meet upswelling sea water, and the water level in the crack seeks to match the sea level surrounding the ice). But here we are talking of a difference of tens of meters between the bottom of the meltpond and the sea level, and the water is able to drain down to sea level.

Floating sea ice is not rigid as an ice shelf, and it is vastly thinner.  And the only circumstances under which a melt pond on an ice floe can be said to "drain" is if the bottom of the meltpond is sufficiently above sea level when cracking occurs to enable the water to disappear from view. I find it hard to imagine such a circumstance, and it certainly does not apply to Glenn's example.

To recap: A melt pond can only be said to have "drained" if the water disappears. This can only happen if the bottom of the meltpond is above sea level when cracking occurs. Most meltponds seem to have bottoms that reach below sea level, hence cannot "drain". But a scenario of thicker ice with a meltpond that bottoms out above sea level is of course feasible, and if such a flow were to crack, the melpond would drain and the weight of the meltpond itself could be a contributing factor to the cracking itself (water being denser than ice and all that, although "punching" is not a good way to describe this). But this is extremely unlikely to be a significant factcor in arctic ice melt, which was what Glenn's original post was about.

41
Arctic sea ice / Re: The 2020 melting season
« on: September 04, 2020, 06:17:21 AM »
This is a weird breakup. Can this be because of wave action?
BTW, This is no wave action, as before Aug 31 there was none in that area.
This polynya so visible is probably due to ice surface refrozen, and then broken by deformation of the pack, just as it happens in winter.

(Pic from Aug 31 somewhere in the CAB near Laptev/ESS)
I liked a previous explanation better, that these are "old" floes stuck in FYI that are now becoming visible after the weakest FYI ice has melted out.
Well there is definitely no surface refreeze anywhere this season. We're still a few weeks out from seeing the first measurable refreeze, although meltponds may freeze well before that and may already have frozen and thawed several times already this season.

42
Arctic sea ice / Re: The 2020 melting season
« on: September 03, 2020, 04:13:04 PM »
mdoliner

"Melt ponds cannot drain. nine tenths of the floe is below sea level."

Imagine a floe 2 meters thick, 20 cm above water level. A melt pond forms in the middle of it, 40 cm deep, but not in contact with the ocean below. Then cracking allows it to drain.
I'm not sure if that could happen. If the ice cracks, seawater from below will push it's way into the cracks until it reaches the meltpond, at which point the surface of the meltpond will fall down to sea level. The weight balance of the ice floe would change slighly, but the melt and cracking needed to connect the meltpond to the underlying seawater would probably involve a much greater disturbance.

But the water in the meltpond cannot "drain" down through 1.6m of ice to somehow pour out into the surrounding ocean at a depth of 1.8 meters (in your example) - what force would compel it to take on such a journey? Not gravity, that's for sure.

In fact, talking about meltponds "draining" is probably meaningless. If the ice that seperates the meltpond from the underlying seawater melts or cracks, the water level of the meltpond will change to match the level of the surrounding ocean by mixing with the intruding seawater. But this slight change in the weight balance of the floe is much smaller than the changes required to enable the pond to communicate with the underlying seawater.

Sorry for the tautological posting.

43
Arctic sea ice / Re: The 2020 melting season
« on: September 03, 2020, 06:13:29 AM »
wrt to fg's question: Aren't katabatic winds fairly common coming off of GIS? Wouldn't those be cold enough to (re)freeze coastal waters?

Also, isn't the water just off Greenland quite 'fresh'/less salty because of all the melt from GIS, so it would freeze more easily?
This misunderstanding of anabatic (upflowing) and katabatic (downflowing) winds seems to be quite common. As air rises over a mountain range (or ice sheet) it cools due to a fall in pressure. As it descends on the other side, it warms up again due to increased pressure, so the two effects cancel each other out. This is also called the adiabatic process and is what enables  fridges and airconditioners to work. 

What seems to happen quite often in Greenland is a foehn (or chinook) wind, which is caused when the rising air is humid, causing precipitation and release of latent heat, with the result that once the air reaches ground level again it is actually warmer than before. This can quite often be seen along the north coast of Greenland in Nullschool.

When air blows over a large stretch of ice it will lose heat to the ice, so in the case of Greenland ice sheet, dry air that does not experience the foehn effect will presumably be somewhat colder on theleewards side.

As for meltwater runoff from Greenland, the major part of that happens during summer. Almost all the major sources of runoff face the East Greenland Current or it's extension, the West Greenland Current, and  any runoff is carried away fairly fast and effectively disappears in these two currents and is nowhere near the Arctic by the time refreeze kicks in.

44
Arctic sea ice / Re: The 2020 melting season
« on: September 02, 2020, 09:50:07 AM »
Another, older, paper on the subject of bathymetry and SIE.
Nghiem et al, 2012. Seafloor control on sea ice. Deep Sea Research Part II: Topical Studies in Oceanography (Link)
Abstract
Thanks Pansa. But reading these two quotes makes me more confused than not. It seems that when Nghiem et al say that bathymetry has a "profound" effect, they seem to be at least partially talking about the shoreline - i.e. that ice maximum doesn't change much from year to year because it is constrained by the shoreline. And the shoreline is apparently a part of bathymetry. Which is indeed a major effect! Other than that it is mostly general observaions that I think we all could agree with.

In the second quote from NSIDC i read the following with wonder and consternation: "At its seasonal minimum extent, the ice edge mainly corresponds to the deep-water/shallow-water boundary (approximately 500-meter depth)" ... well perhaps in times past but not in recent memory.

45
Arctic sea ice / Re: The 2020 melting season
« on: September 02, 2020, 09:39:25 AM »
The ice retreats from the south, and by far the biggest factors are heat and insolation.
This one is interesting - on Oceanic Heat Transport (OHT) & Atmospheric Heat Transport (AHT). Ocean heat transport more important.
Exactly what I would expect, and I'm surprised that it is only a factor of 2.

46
Arctic sea ice / Re: The 2020 melting season
« on: September 02, 2020, 09:03:14 AM »
The ice retreats from the south, and by far the biggest factors are heat and insolation. Salinity and bathymetry are bumps on the way from maximum to minimum.

Salinity changes with ice cover, so correlation is not equal to causation. Currents fluctuate and are most likely also changing due to decrasing ice cover. Bathymetry is static, and doesn't really make any difference for either seasonal melt or long-term decline.

47
Arctic sea ice / Re: The 2020 melting season
« on: September 02, 2020, 08:51:19 AM »
Its clear as day that there is a major correlation between bathymetry and the ice edge.


It is much harder to melt ice over the super deep parts of the Arctic
Why should it be "much harder"? And what research have you or others done to establish a "major correlation"?

There is correlation, but there is also the co-incidence of the deepest waters being furthest north, and on the Atlantic front, sheltered by a string of islands. Both of these factors could be responsible for a stronger apparent correlation than the what is in fact happening.

48
Arctic sea ice / Re: Poll: Where will the last Arctic Sea Ice be located?
« on: September 01, 2020, 02:26:50 PM »
...it would also be moving very rapidly, and it's location totally dependent on the general wind direction of that melt season.

True for all options except one: 'within the Canadian Arctic Archipeligo', which is why I chose it.

If it was last 0.1m km2 then this would make sense to me. But I find it hard to imagine as much as .5m within archipeligo so with last 1m most is going to be outside.

I voted for after 2035, the scientists seem to have agreed on slowing rate of loss. When was the last time it wasn't boringly on/near the low edge of past years? 2012 maybe?
I don't see what the "archipeligo" has to do with my posting, but then again there are many things in this world that I don't understand.

But I'm pretty sure we'll see BOE before 2035 and I am wondering what scientists you are thinking of that have "agreed" on anything, let alone on slowing rate loss.

49
Arctic sea ice / Re: The 2020 melting season
« on: September 01, 2020, 11:49:44 AM »
Does this image end the debate about bathymetry and the ice edge? The ice edge clearly doesn't care about bathymetry...
I didn't know there still was a debate about bathymetry. I seem to remember having started just such a debate a few years ago, and after much heated argumentation and wild claims, I believe the real physics behind any link between the ice edge and bathymetry was teased out.

And the only area where I was convinced that bathymetry had a real effect was where the warm Atlantic waters get room to sink once they are past the Svalbard / FJL line. Another real effect is the shallowness of the Siberian seas, which makes water movement much less pronounced but are too shallow to have proper stratification, hence rapid and extensive mixing once ice-free.

But these are secondary effects. There is no primary effect between bathymetry and the ice edge, and since a lot of other factors come into play as well, any link with bathymetry can only be considered transitory and weak.

50
Arctic sea ice / Re: Poll: Where will the last Arctic Sea Ice be located?
« on: September 01, 2020, 05:39:47 AM »
Interesting poll, but I am unable to vote since I am not seeing any option that fits what I think will happen once the ice goes under 1m km2.

In my view, once we get below a certain threshold, the rest of the ice will be dispersed and blown all over the place.  I don't expcect there to be any "center" to the remaining ice, but if it so happened that all the ice was continuous then it would also be moving very rapidly, and it's location totally dependent on the general wind direction of that melt season.

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