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Messages - RoxTheGeologist

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1
Arctic sea ice / Re: The 2020 melting season
« on: June 12, 2020, 05:50:24 PM »
Everything looks terrible for the ice but it has before and little melt has resulted.

I think, Armageddon's Blade is ready and possibly waited for this message. :)

earth.nullschool.net, 16.06.2020 00:00 UTC, 850 hPa.

1. A WAA near the Lena Delta. Temperature is 7.4°C. Doesn't sound outstanding. But wind speed is 90 km/h.
2. What about water vapor? 29.72 kg/m2.
3. Though it's just one point. How big is this WAA? It's everywhere.
4. Weak clouds don't provide good protection from the Sun.

Water vapour has a high enthalpy of vaporisation. That heat can melt approximately 4x it's mass of ice as it condenses. High winds blowing over warm and wet Land is an effective way of transferring heat into the ice. In this case, each 10M3 of air can melt 1M3 of ice.



2
Arctic sea ice / Re: The 2020 melting season
« on: April 20, 2020, 09:39:52 PM »

Also:

When insolation < emission, snow is bad as it insulates and prevents heat loss.
When insolation > emission, snow is good as it prevents the ice heating up.


3
Antarctica / Re: PIG has calved
« on: February 11, 2020, 07:26:06 PM »
Yes, that's what i think too.

And for how i see it, no one here thinks differently on that one.

It's going to be interesting to see if that whole 'wedge' of fractured ice clears out and we get calving along that face from both the PIG and the Ice sheet.


4
Antarctica / Re: Thwaites Glacier Discussion
« on: January 30, 2020, 10:26:27 PM »

Thanks ASLR, that makes a lot more sense now. I didn't consider the pressure changes on melting temperature.

5
Antarctica / Re: Thwaites Glacier Discussion
« on: January 30, 2020, 07:47:55 PM »
Scientists Find Record Warm Water in Antarctica, Pointing To Cause Behind Thwaites Glacier Melt
https://phys.org/news/2020-01-scientists-antarctica-glacier.html

A team of scientists has observed, for the first time, the presence of warm water at a vital point underneath a glacier in Antarctica—an alarming discovery that points to the cause behind the gradual melting of this ice shelf while also raising concerns about sea-level rise around the globe

... The recorded warm waters—more than two degrees above freezing—flow beneath the Thwaites Glacier, which is part of the Western Antarctic Ice Sheet. The discovery was made at the glacier's grounding zone—the place at which the ice transitions between resting fully on bedrock and floating on the ocean as an ice shelf and which is key to the overall rate of retreat of a glacier.

... "The fact that such warm water was just now recorded by our team along a section of Thwaites grounding zone where we have known the glacier is melting suggests that it may be undergoing an unstoppable retreat that has huge implications for global sea level rise," notes Holland, a professor at NYU's Courant Institute of Mathematical Sciences.

... Aurora Basinski, an NYU graduate student who made the turbulence measurement, said, "From our observations into the ocean cavity at the grounding zone we observed not only the presence of warm water, but also its turbulence level and thus its efficiency to melt the ice shelf base." ... "This is an important result as this is the first time turbulent dissipation measurements have been made in the critical grounding zone of the West Antarctic Ice Sheet."

https://thwaitesglacier.org/projects/melt

2°C above freezing, so that would be....? Is that 0.2°C (assuming saltwater at -1.8°C) or 2°C? The latter is scary, the former, that's not much above the melt point of the freshwater glacier. Basically an order of magnitude less energy to melt the glacier. that 10x difference may become important....

6
Science / Re: Where are we now in CO2e , which pathway are we on?
« on: January 25, 2020, 11:53:48 PM »
While writing these lines a further question came into my mind:
Is a simple addition right at all? Maybe the IR spectra of the molecules (especially CO2 and N2O) overlap and reduce each other by some interference?

The overlapping (or not) of spectra is already built into the GWP.

One think I am not sure of is if aviation emissions are counted correctly, as they are largely in the stratosphere.

7
Arctic sea ice / Re: Near Real Time Sea Ice Volume
« on: January 15, 2020, 06:50:38 PM »
Thanks for the thread. Volume is more important than area or extant.

Well, except for aldebo and the whole Arctic amplification thing.

8
Arctic sea ice / Re: The 2019/2020 freezing season
« on: January 09, 2020, 07:07:14 PM »
I'm still wondering what has changed to increase the ice in the Barent Sea over the last year.
Perhaps the ice is more mobile. osi-saf drift sep21-jan6

Thanks for the animation! Ether more cold input or less heat or a bit of both. It could be that there is much more ice being pushed out over the Barents, that the yearly changes are just noise. We remain avid observers.

If you had to pick one visible symptom of a slowing AMOC in a warming world? For me it would be less heat in the Barents, and more ice, it's far to the North and only the AMOC's heat keeps it ice free.

9
Arctic sea ice / Re: The 2019/2020 freezing season
« on: January 08, 2020, 06:07:38 PM »
Aren't the poles the only places where the planet can lose its heat? I'm thinking that if there would be more ice, that the Arctic would be colder and able to release more heat into space, overall cooling the planet, and giving us more time before the feedback loops kick in and the climate runs out of our control.

The Arctic is heating up faster than any other place on earth, so cooling it down seems logical to me. And I don't think this would heat up the rest of the planet more.

This is entirely wrong. Hot things emit more heat than cool things. The low latitudes gain heat through insolation. The whole planet is losing heat all the time, more rapidly at the low latitudes as they are warmer. The disparity in insolation heating causes the atmosphere and oceans to operate as heat pumps, transferring heat from the low latitudes to high latitudes and increasing the overall efficiency of heat loss. If you stop the transfer of heat to the poles you reduce the ability of the earth to lose heat.

10
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: December 11, 2019, 07:25:16 PM »

Barents - will above average sea ice area continue?


Barents: I'm curious as to why we started seeing encroachment onto the Shelf. for a few years there was little ice on the shelf because of (presumably) Atlantic water effectively melting ice as it crossed the continental shelf before flowing down the slope. Why is less warm water (or more cold water) finding its way to the shelf boundary and increasing extent? Has the AMOC slowed?; Is the warm water deeper; is it finding its way around to the Nares? Should I post this on stupid questions?

11
Arctic sea ice / Re: The caa-greenland mega crack
« on: October 31, 2019, 05:32:13 PM »
Blumenkraft,

Every year in the freezing season, the volume of the Arctic sea surface expands by roughly 10 percent (due to the fact that density of sea ice is lover than that of sea water). If everything (including air pressure and sea level) remains constant, something will have to give in. . . .

I don't think that's how the physics works.  Certainly Nares and Fram surface currents are more robustly southward in winter than summer.  But not, I think, because sea water is freezing.  Sea ice displaces its *weight* and not its volume. 

Just as the water level in a glass of ice water doesn't change as the ice melts, neither does it change if ice forms in the glass.  Thus winter freezing of sea water into sea ice doesn't create any net change in forces of flow (all other changes being equal, which they never are in actuality).

I don't have an explanation for the observed seasonal flow patterns, but I'm pretty sure volume of ice formation isn't it.

If you put a piece of ice in a glass of saltwater, the freshwater from the ice flows to cover the saltwater. Freshwater/ice from the arctic is less dense and therefore there is an elevation difference. Hydrostatic stress is the same but the diviatoric stress makes the water flow (as its incompressible). its a long time since I did any continuum mechanics so my explanation may be wonky. Water flows downhill?

12
Arctic sea ice / Re: "Stupid" Questions :o
« on: October 25, 2019, 06:35:24 PM »

...
But the fundamental mechanism of sea ice formation (which you seem to have forgotten here) is that sea water is densest at freezing point, which means that before any ice has time to form, the surface water starts sinking and mixing downwards, and the underlying warmer waters start to move up.

This is presumably what is happening in all the open areas of the arctic right now. Very cold air is blowing in from the south (from Siberia) and from the ice itself, but the air heats up very rapidly over the open ocean where the sea surface temperatures are above freezing.
..


Isn't the mixed layer in summer salinity stratified? Salinity has a much greater impact on density than temperature. I thought that the freshwater lens from melting ice effectively prevented any convection, maybe if the water to 10m (?) has been warmed and homogenized it will turn over as the surface cools.

Sadly we don't have enough buoy data to really get a good picture of what is happening to seas like the Chukchi, distant from rivers, and with much longer exposure to wave and current action because of the early ice loss. It might be that as the sea becomes ice free for longer, the ocean becomes homogenized to deeper levels, evaporation concentrates salt in the surface, sea ice takes longer to form and is thinner and works as a positive feedback year on year.

And no, I didn't suddenly forget the properties of salt water :) If it were freshwater, the warming and melting in the spring would cause the water column to turn over (like a temperate lake).


 

13

What? Do they not give more weight to which journals publications papers are in? That's terrifying.

Peer review is not a perfect process. A biased editor can easily send a paper to review by like minded scientists or economists, particularly as it is hard to find editors for less well respected journals.

As far as I know the IPCC is a political creation, designed to put bias onto scientific results. It gives the opportunity for a nation to weigh a paper published in EPSL as highly as one published in less renowned journals. That's particularly true when it comes to counting the cost of climate change, and exactly how to measure financial risk. Even if everyone accepts that climate change is real and anthropogenic, there is still an argument to be muddied about whether it is better to pay now or pay later.

14
Arctic sea ice / Re: The 2019/2020 freezing season
« on: October 22, 2019, 05:46:08 PM »
Quote
It is also fascinating that so little attention has been paid to this ongoing event on this forum. Nevertheless, it would appear that accumulated heat in the Arctic Ocean/system is an important factor.
Many have nothing to add and don't want to get yelled at for cluttering up the thread with their inane chatter.
Albedo, ocean heat content , decline of old ice .
Weather is the other factor.
One would suggest that weather is all that is stopping A BOE in the near term.. less than a decade.
Then it will get truly interesting.

My understanding is this: The heat lost through emission into the atmosphere is what cools the Earth. There isn't enough insolation to balance the heat loss through the year at the poles. The oceans and the Atmosphere transfer heat to the poles from the tropics where insolation is greater than the heat loss from emissions. The Arctic ocean is effectively insulated from oceanic transport by the continually refreshed halocline. The only way to create a BOE is transport of heat and water vapor by the atmosphere to north of 80 degrees, even from the surrounding peripheral seas. I'm not sure if this is what you mean by weather? If it's cold then there wont be a BOE, if it's warm and wet then there will be?



15
Snow is an insulator and a reflector. It prevents the earth losing heat and increases albedo. I foot of snow is equivalent to R15 insulation. It doesn't matter if the year was a "cold" or "warm" one, the difference is that the surface of the ground is insulated against emitting heat into space, the "ground" surface doesn't drop to -40 C or what ever the ambient temperature is. The contrast one has to consider for the analysis is the difference between winter and summer temperatures, not year on year changes.

Albedo is more important when the balance of heat loss prevented by the insulation throughout the day is less than the amount of heat added from insolation. If snow cover DOES persist into the summer then one, clearly, can make an argument that heat into the earth from insolation is going to decrease. From Shared Humanities post, the evidence is that this is not happening. Snow is melting out rapidly in the spring.

Basically we apply a nice reflective blanket in the cold of the night, to keep the heat in, then we pull it off as soon as there is enough warm sunshine to heat up the ground. My guess is its a strong positive feedback loop into warming the earth.

There will be nice deep early snowfalls from a meandering jet stream and an increasingly wet atmosphere, the latitudes that the snow will persist into spring will move north. The permafrost that relies on winter heat loss will thin and decline in extent, releasing more methane and CO2 and feeding the increasingly warm wet cycle towards an equitable climate.

The above are some of the feedbacks that amplify Milankovitch cycle variations. The cycles themselves don't change the heat input into the earth enough to cause the variations that we observe in previous interglacials. We are in a Milankovitch interglacial now and have accelerated the feedbacks by the release of gigatons of CO2.

16
Arctic sea ice / Re: The 2019/2020 freezing season
« on: October 10, 2019, 06:30:49 PM »

My opinion is this season demonstrated that there isn't enough insolation to melt the ice above 80N from a 'normal' freeze season. Too much ice is built up and it doesn't receive enough energy directly from the sun.

For that 4m km2 to melt out there has to be more heat and therefore less ice (duh!). That heat has to come from the atmosphere through the 9 months of the year that insolation isn't dominant, or from the ocean as the result of a big storm or two late in the melt season.

This part of the freeze season is critical, if the seas south of 80N are warm then there will be less Freezing Degree Days over the main pack. Increased water vapor will effect any energy transfer, such as fog over the ice edge preventing both heat loss and the vaporistation/condenstation cycle transferring a lot of energy, and perhaps from snowfall providing insulation to the ice.

It's going to be interesting to watch the next couple of months to see if the thickness of the central pack grows slowly...






17
Arctic sea ice / Re: The 2019/2020 freezing season
« on: September 27, 2019, 08:24:44 PM »

More snow = more sunlight reflected = cooling. 

Not cooling but less or later warming, that's not the same.

Cooling would happen if temps would generally be lower than before but as they are generally higher (AGW!) we have reduced/later/ warming over snow covered area than over not snow covered area.

The biggest problem with more snow is that it makes it harder for the permafrost to refreeze, and that would lead to warmer landmass during summer, and more methane in the air.

Early snow traps heat in the ground and in the ice. Instead of the surface being able to radiate heat directly to and through the atmosphere (say - 40°C) it has to conduct the heat through all those nice air pockets in the snow. On sea ice it would effectively lower the number of FDDs

Early snow = slows down heat loss (insulator)
Late snow = slows down heat gain (albedo, specific heat of melt to overcome before ice and ground heat up, insulator)

Of course and model would depend on the latitude and time of year


18
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: September 24, 2019, 06:32:50 PM »
When looking at the AREA graphs for the principal seas that surround the Central Arctic sea, the Laptev, ESS and Beaufort all came in well under the 2010's average.

Quite a substantial difference from the Central Arctic, the area of which is now greater than the 2010's average AND the 2000's average.

I think much of that is down to the Atlantic side of the Arctic. In the last few years before 2019 that ice age has been pushed back well over the edge of the continental slope. This year the ice remained in contact with Svalbard for the whole season. Perhaps it's correlated with the Nares strait not closing? If more Atlantic water is being diverted around Greenland that would explain less melting around Svalbard.

19
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: September 20, 2019, 10:53:29 PM »
Neven, are you reopening the refreezing thread today or tomorrow?  ;)

The fat lady has finally sung...

Great job Gerontocrat and Juan C. Garcia, thank you both 8) 8) You have earned a very well deserved rest now :)

Are you sure - 2018 had a big drop today, and without increases the 5 day average is still going down thanks to the century break a couple of days ago

20
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: September 20, 2019, 09:52:39 PM »

And from me too. Thank you for all the excellent data and analysis.

21
Arctic sea ice / Re: "Stupid" Questions :o
« on: September 20, 2019, 09:49:36 PM »
As kindly suggested I apply to those of you who 'get it' here: Why should there be any connection between ocean depth and surface ice. The assumption that deep water in the CAB should somehow protect the ice keeps popping up, but why should that be the case?
...
- There is a mixed layer, top 50 m. This layer is called mixed because, thanks to the action on the surface by winds, waves, etc., the mechanical input is able to mix differences in temperature and salinity by induced turbulence. It is strong enough to keep stratified layers from forming. Curiously the mixed layer has an increased salinity in most oceans except in the Arctic Ocean, which mixed layer is much fresher than at higher depths. The mixed layer ends by an abrupt salinity increase called halocline.

What makes the water of Arctic ocean mixed layer "fresh" and cold relatively? I think it's rivers, and the fact that the halocline comes before the increase of temperature, deeper under the halocline. So thanks to this strong stratification layer, the heat from beneath won't reach the mixed layer, staying relatively cold, and relatively fresh. I think there's a physical explanation for the halocline coming at lower depth than the temperature increase from deep waters, but I don't remember it. If it was not the case, there would not be Arctic ice, probably.
...
PS. Wikipedia page of the Arctic brings some interesting facts...

Thanks for that explanation. As Uniquorn points out, it is not as "idealized" as what you explain or the halocline/thermocline description in Wikipedia, but it seems THE factor: given the conditions of the Arctic Ocean, the halocline exists wherever the ocean is DEEP, inhibits mass and heat transport from the SUNK Atlantic and Pacific waters beneath, BUT the protective effect of the halocline has no room in SHALLOW shelves (peripheral seas of the Arctic proper). Temperature changes happen mostly UNDER the halocline, which helps BIG TIME the survival of the CAB in summer.

I think it is a rational explanation linking DEEP waters and SURVIVING ice.

The relationship between sea ice and bathymetry is well understood, particularly on the Atlantic side of the ocean. The warm salty waters from the Atlantic sink below the fresher Arctic waters from the Atlantic waters in under the Nansen basin. On the Pacific side the warmer Pacific waters in the Chukchi sea form the deeper waters under the Beaufort Gyre. The ice edge closely tracks the edge of the continental shelf in the summer on the Atlantic side of the Arctic.

The Freshwater cap on the Arctic is replenished by freshwater from melting ice and from the rivers, (I think about 50/50 from what I have read. The Siberian shallow seas are freshened because of the distance from the oceans and the big rivers that drain onto the shelf.

The mixed layer depth varies seasonally. In the summer it becomes shallow, there is little mixing and lots of input of freshwater causing stratification. In the winter as freezing starts the formation of ice expels dense brine that causes convection in the upper layers, and the mixed layer deepens, perhaps all the way to the halocline.

22
Arctic sea ice / Re: The 2019 melting season
« on: September 18, 2019, 06:25:46 PM »
And what is the approximate area of Arctic Ocean with depth>100m ?
That simple thought has more meat from a physics point of view than the 07 12 16 19 thing (cute signature though).
Of course the Arctic resists melting because warm water sinks at the shelves breaks. The core is not only atmospherically more protected, it does not get ocean heat at all either!
But my feeling is that a summer with a very ice-dispersive weather like 2016 will eventually melt most of it.

Although it sounds compelling, I've never really been convinced by the bathymetry argument, i.e. that deeper waters somehow protect surface ice.

The main objections I have are as follow:

1) Warm water does not sink


If the warm water is more saline it does.

23
Arctic sea ice / Re: The 2019 melting season
« on: September 17, 2019, 07:14:03 PM »
It is interesting to note that there is a pattern to the very bad years of 2007, 2012, 2016, and 2019.

The first "bad" year was 2007. It took five years for 2012 to happen. It took four years for 2016 to happen. It took three years for 2019 to happen.

Perhaps it is nonsense, but that would put 4M KM^2 minimum as "normal" come 2021 (two years after 2019, and then we are down to one year separating these instances, i.e. it becomes each and every year), with each year thereafter likely to achieve a max under 2019, 2016, and 2007.

It should also be noted the last minimum above 5M KM^2 looks to be 2009. That is potentially about 11 years between the last minimum above 5M KM^2 and the last minimum above 4M KM^2 (using the step-trend above, that year would be 2020, or it may have already occurred).

We cannot say whether the remaining decline will follow on the same gradual continuum. Below 4M KM^2, the area / volume discrepancy inherently favors massive drops in area relative to volume as 0 is approached. I would think that there will not be another 11 years between the last 4M KM^2 min and the last 3M KM^2 min.

Does that mean we are approaching an asymptote at 4 M?
Maybe temporarily but I think the volume decline means it will not hold. Maybe it is a situation of once the asymptote is breached twice consecutively it cannot recover and spirals to near 0. Until it happens two years in a row, or rather until now, there has been sufficient momentum for temporary recoveries. As we can see in the year over year charts that momentum has been fading.

I suspect the total insolation above 80°N (from observation) is too little to melt the ice that forms on a yearly basis. The ice will have to be thinner, so less FDD days or more export. That equates to warmer and wetter weather for 9 months of the year. That or some good big storms to mix the ice with the warmer water below the halocline or in the adjoining seas during the summer.

The area within 80°N is 3883031 km2 (please someone correct that math if I'm wrong!) so perhaps that is where we will asymptote, give or take a little due to land masses causing local patterns. That may persist until we build up enough imbalance between the polar and equatorial temperatures to drive additional heat into the Arctic in the form of big warm storms.



 

24
Arctic sea ice / Re: The 2019 melting season
« on: September 16, 2019, 06:37:45 PM »
JAXA/ViSHOP extent has now fallen below the 2016 minimum:

http://GreatWhiteCon.info/2019/09/the-2019-arctic-sea-ice-metric-minima/#Sep-16

Only 2012 left to beat!

That's quite a big gap. Perhaps not this season. I'm just hoping it drops another 7k so the result drops into the correct bin. By correct I mean the one I voted for.

25
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: September 15, 2019, 07:22:53 PM »

Whenever a curve or line is fitted to a graph it is to illustrate a correlation; such a correlation is the decline in sea ice volume over the last few decades. I'm no expert in sea ice modelling but, there is a fundamental need to understand how one would apply a model to be able to predict future conditions.

To understand a correlation a model is built. The model can perhaps take the starting data and then show how sea ice has changed on a year to year basis (hind casting). It can then be used to predict the future, and it's skill tested by it's ability to do so. Models are only as good as the test conditions applied. Hindcasting can be tricky as there is the temptation to model fit the data.

Obviously models based on a line fit are incorrect, they can be trivial disproved by projecting backwards in time and showing that there wasn't that much ice 10000 years ago. I hear the 'but there wasn't GHG emissions" so immediately the model has to include global warming from GHG gases. Assumptions are disproved, the model improves. If a model can effectively hind cast current sea ice from pre industrial times, then we perhaps have a chance of predicting more accurately what the future holds.

At least correlate global temperatures with sea ice volume, that seems like a better starting point than time.




26
Arctic sea ice / Re: The 2019 melting season
« on: September 12, 2019, 11:55:14 PM »

This makes a big assumption - that system behavior will be consistent as we reach that limit.

Based on the surprising end of season slowdown this year, I'm not sure that's safe. I'm still mulling hypotheses for what we are seeing and why the dynamics are not falling more in line with your assumptions. 

"Blue Ocean" is a boundary condition, and the retreat of the ice to where it stands now - post 2007 - suggests to me that the dynamics for the ice north of 80 are significantly different from those of the peripheral seas, which is were most significant visible changes in the Arctic have unfolded.


This is my thought too; that there isn't enough insolation to melt the ice N of 80°N with the current FDD thickness increase, even in a sunny year. To melt the ice there has to be less FDDs. Increased oceanic heat isn't going to effect the high Arctic sea ice while vertical mixing is prohibited by the halocline. The latter isn't likely to disappear completely because of the input of fresh water from rivers and ice melt. Mixing can occur during big storms, but they seem to be rare in the summer. If that's the case, then seeing the high Arctic ice free is likely to require a warm, cloudy winter as well as a bright summer.

Did I just state the obvious?


27
Arctic sea ice / Re: The 2019 melting season
« on: August 23, 2019, 06:49:54 PM »
At this time of the year, I'd expect calm, cloudy, and snowy weather to be the most detrimental to the longevity of ice in the Arctic. All three work to trap heat in the ocean and atmosphere.

 If the Arctic isn't losing heat as effectively then the Earth is just going to warm up faster. This melt season seems to have been particularly bad. Lots of insolation with blue skys to soak up heat, and now plenty of cloud and some snow to start trapping that heat; extra water vapor in the atmosphere from warm seas surrounding the ice providing the proverbial 'icing' on the cake. There isn't going to be a new minimum, but this is worse.

28
Arctic sea ice / Re: meaningless freezingseason/melting season chatter.
« on: August 21, 2019, 07:35:07 PM »
Quote
Earth gravity variations will not affect anything that floats over a iso-potential surface because these variations have already been accounted for in the level variations of the iso-surface. Nothing that lies in this iso-potential surface will feel gravitational pull parallel to the iso-potential surface. BECAUSE BY DEFINITION THE GRAVITATIONAL FORCE IS PERPENTICULAR TO THIS SURFACE.
Umm the shouty bits do not make it more true.
The mass of the Greenland ice sheet is above your theoretical surface.
The ice sheet has a gravitational pull perpendicular to its mass .
When the ice is gone the gravitational effects in the local area change.
Lowering  the surface of the water nearby.
The same effect will happen in antarctic resulting  the polar sea levels falling and higher seas  the nearer you get to the equator.

http://sealevelstudy.org/sea-change-science/whats-in-a-number/attractive-ice-sheets

You are both right! SIS is correct, as are you. All things being equal water follows an equipotential surface  that is perpendicular to the gravity field. As ice melts, mass is redistributed and the shape of the surface changes, and be inference, water level. I think it's confusing as we think of things flowing up and down 'hills' but in reality, in terms of the 'hills' on the geoid, the hills are flat....

29
Arctic sea ice / Re: The 2019 melting season
« on: August 21, 2019, 07:02:32 PM »

isn't early season snow good for slowing ice loss but increases long term heat retention?

30
Arctic sea ice / Re: meaningless freezingseason/melting season chatter.
« on: August 19, 2019, 11:23:03 PM »
Back to the problem of ice being lovely attracted to Greenland. From first principles (Newtonian):

Gravitation: a conservative force from which a potential energy field can be derived.
Ideally, water fills the oceans following a constant iso-potential surface. It will be almost horizontal, but in some places with more gravitational pull, the level will be depressed, and in others, will be higher than average.
This is a static effect. Earth gravity variations will not affect anything that floats over a iso-potential surface because these variations have already been accounted for in the level variations of the iso-surface. Nothing that lies in this iso-potential surface will feel gravitational pull parallel to the iso-potential surface. BECAUSE BY DEFINITION THE GRAVITATIONAL FORCE IS PERPENTICULAR TO THIS SURFACE. And in the case of an ice block, this is balanced by buoyancy force due to the water being denser than ice.
Same happens with earth inertial centrifugal force, proportional to the distance to the earth axis. It can be derived from a potential field, which combined, distorts a little bit the gravitational iso-potential surfaces.

Coriolis inertial force, however, is the tricky one, since this cannot be made a conservative force, it depends on the relative velocity of the ice block with respect to the Earth.

The coriolis force appears in all kinds of interesting problems of the Arctic. I would recommend to read about it rather than quantum mechanics (in the context of the Arctic). It's less attractive to discuss while smoking a joint and looking at your gin-tonic ice cubes sticking at the sides than, say, quantum mechanics paradoxes and dragons.

The geoid is a map of the equipotential surface, represented as a departure from a reference ellipsoid (the mathematical approximation for the earth). The equipotential surface includes rotational effects. It is changing slowly, from ongoing PGR and ice melt. As sis says, since it is an equipotential surface by definition gravity is always perpendicular to a tangent to the surface.

31
Arctic sea ice / Re: meaningless freezingseason/melting season chatter.
« on: August 19, 2019, 11:13:24 PM »
Oh, this should be here too...

Ups and downs from PGR

32
Greenland and Arctic Circle / Re: What's new in Greenland?
« on: August 19, 2019, 11:10:01 PM »

Here's a map of the ups and downs.

33
Arctic sea ice / Re: The 2019 melting season
« on: August 19, 2019, 05:43:33 PM »
My theory is that Greenlands mass pulls the ice towards it.

I like your theory, it makes a lot of sense.

You can look at what the surface of the ocean would like like given the effects of gravity and the rotation of the earth, it's the equipotential surface - the geoid

34
Consequences / Re: Laurentide II
« on: August 13, 2019, 07:56:44 PM »

I posted a question on stupid questions noting that early and heavy snowfall is probably a good way to heat up the planet as it does a very good job of insulating against heat loss that would otherwise have been going on.

35
Arctic sea ice / Re: The 2019 melting season
« on: August 13, 2019, 06:06:22 PM »

It would be interesting to know how much ice the Barnes Ice Cap lost this yet. It seems to have been under blue sky for most of July and August.

A remnant of the last ice age. It will not survive to see the next.


Next ?


100,000 years from now

We are STILL in an ice age. What we are experiencing is the Earth's climate transitioning from a interglacial to a hothouse state. My guess is it'll take a few million years to switch back to icehouse. Go on; Prove me wrong.

36
New CESM2 runs are indicating that the most likely value for ECS is 5.3C:

Oh S**t.

37
Arctic sea ice / Re: The 2019 melting season
« on: August 12, 2019, 01:37:20 AM »
I am amazed how easily the human is deceived and can "see" patterns with minimal data....

Canals on Mars.

38
Arctic sea ice / Re: "Stupid" Questions :o
« on: August 05, 2019, 12:43:12 AM »
Q. Can it? My response to this statement on the 2019 Melting Thread.

There is more than enough heat in the deep water to melt the ice and keep the arctic ice free year round. 

However, the heat can not move upwards through the halocline. 

The halocline is 50 meters thick (at least) and is very difficult to breach.  If it ever happens, look out!   The arctic will be a completely different place.


I've often wondered if/why the thermal conductivity of seawater is insufficient for significant melting of the ice just by thermal conduction, when the halocline is stable.

So let's see...


Consider the year-round loss of ice thickness due to thermal conduction from a 1-degree-C-warmer layer at a 50 meter depth.


ASSUMPTIONS & PROPERTIES:




CALCULATIONS:

Upwards heat flux = (temperature gradient) x (thermal conductivity) = 2e-2 K/m x 0.6W/mK = 1.2e-2 W/m^2

Thermal energy added to ice in 1 year = (Upwards heat flux) x (time in 1 year) = 1.2e-2 W/m^2  x 3.1e7 s = 3.7e5 J/m^2; multiply by 1e-4 m^2/cm^2 = 37 J/cm^2

Depth of ice melted = thermal energy added / (heat of melting x density)
= 37 J/cm^2 / (334 J/g x 0.9 g/cm^3) = 0.12 cm depth



CONCLUSIONS

So the thickness of ice melted over a year in the above scenario is only of order a millimeter.

Indeed, the thermal conductivity of seawater is insufficient to provide significant melting from deep layers of warmer, saltier water below the ice.

The layer down to the halocline is typically mixed as the ice freezes. Cold briny water is formed from expulsion, sinks and the upper layer becomes mixed.

The strong stratification in the melt season is unlikely to allow much heat to propagate by conduction. I'd expected much more heat to be transferred as ice freezes, and to stop it thickening as quickly throughout the freeze.



39
Arctic sea ice / Re: The 2019 melting season
« on: August 02, 2019, 09:05:18 PM »
My hunch is because the 2012 GAC did a lot to release heat that was entrained in deeper waters, 2013 and 2014 had less melt.

Very interesting point that I hadn't considered before.

The thin ice on the Greenland coast may also be indicative of heat building in deep waters. It's far north, and we have had plenty of Pacific to Atlantic drift this year, so why isn't it thick as usual? The only reason I can see for it being thinner is that the water is warmer! It strikes me that it's likely to be representative of the increasing heat build up in the intermediate waters. I'd say it would take a long time for extra heat to impact the surface, as it has to conduct through the halocline. If it is driven by conduction we wont be able to observe it with SST or salinity changes, so to test the theory we would have to have consistent buoy records going back a decade at least.


40
Arctic sea ice / Re: The 2019 melting season
« on: August 02, 2019, 08:35:22 PM »
I still can't make up my mind which one looks worse: 2012 or 2019, but 2019 is more fearsome.

To my eye (and most graphs), on this day 2019 looks worse. But given that the 2012 GAC was this week, it won't be for long. Unless...

My hunch is because the 2012 GAC did a lot to release heat that was entrained in deeper waters, 2013 and 2014 had less melt. 2019 looks like it is on trend, and that 'normal' conditions are getting close to 2012. I wont hold my breath for 'recovery' years in 2020 and 2021.

41
Arctic sea ice / Re: The 2019 melting season
« on: August 02, 2019, 08:20:16 PM »
Here's Neven's year-to-year comparison maps for Arctic sea ice on 1 August.


2019 definitely appears to be one of the worst years on this date. How bad will this melt season end up compared to previous worst years? Too early to tell?

What's really noticeable is the difference on the CAA and Greenland side of the Arctic, compared to all other years (except, perhaps, 2016). There appears to be thinner ice extending hundreds of KMs offshore where the store of MYI used to be.

42
Greenland and Arctic Circle / Re: Greenland 2019 Melt Season
« on: July 31, 2019, 10:06:31 PM »
Just some incredible skew-ts. A few others with freeze levels above 4000m.

This is a subtropical airmass. I've found myself saying this a few times over the past couple of years, but this doesn't belong north of the Arctic circle -- virtually ever.

Thank you for your professional and, therefore, even more terrifying analysis.

43

I think if you really want to know where we are heading with emissions you simply have to follow the money, and investment banks have yet to actually stop funding oil, coal and gas infrastructure, and we have yet to control deforestation and industrial farming. It's not looking good.

That infrastructure has a long lead time to spend the money, 2 years or so, and then usually has a ROI over 10 years and thereafter it makes money. If the money is still flowing towards oil and gas how can we expect emissions to stop growing?

44
Arctic sea ice / Re: Arctic Image of the Day
« on: July 29, 2019, 09:32:06 PM »

One is a picture of a floating iceberg in front of the boat. It could have come from anywhere. Find an old picture of an iceberg then take a picture without an iceberg there.

45
Arctic sea ice / Re: The 2019 melting season
« on: July 26, 2019, 09:24:53 PM »
@jdallen, Yeah definitely. Bottom melt gradually ramping-up , all that mess over Beaufort ESS and even Laptev has time to melt out. August + 3 weeks ahead, and bottom melt doesn’t stop until end of october for the warmest ocean areas.
BTW water warmed by radiation can mix with water beneath the ice. A slow process enhanced with movement. Why people think now it’s like oil on water? In the Beaufort certainly the salinity differences are relatively small.
And even part of Chukchi water can mix while in the shelf before sinking. We see those fingers that the currents form causing eddies engulfing half the warm water and half the pack. After mixing, which takes time in those structures , density stratification is less prone to happen and water temperature beneath the ice must increase.
I don’t believe that the fast edge retreats we observe in late years is not directly enhanced by warm currents from Pacific.

It's been well observed that the ice edge tracks bathymetry. The Barents continental slope often delimits the edge of the sea ice between the Barents Sea and the Arctic. This season the ice  pretty much tracks the continental slope of the Canadian Basin, except in the most southerly regions, the Beaufort. The reason is that the typically saline ocean waters cool and sink as they meet the ice edge, and that water can only sink when it reaches the continental slope.

Water temperature beneath the ice in the basins does increase at depth, but it doesn't mix with surface waters. Ice melts from the edges for a good reason. If the central pack is to melt, it isn't going to be from mixing with warm water from adjacent seas unless the ice gets spread out and deeper waters are mixed by a GAC. The Atlantic water under the Nansen basin already contains enough heat to melt all the ice. The pack will melt because it's thin and from the weather, insolation and air that is extra warm and wet because the peripheral seas have little ice.

Ice melts from the bottom, because the salinity means that it can melt at lower temperatures. if the surface of the ice is at 0°C and the base -1.8°C, any heat input into the system will melt the base at equilibrium, and not the surface. It's a balance between the conductivity of the ice, it's thickness, and how much energy is being put into the surface.

46
Arctic sea ice / Re: The 2019 melting season
« on: July 26, 2019, 05:52:01 PM »
Likely that both are.
Well i wouldn't say "likely" (also, no scorning, remember? :) ) , - but "possible" both are, yes. Which is why i used "at least" in the post you quoted, you see.

But which way? I mean, if you say it's not 2m+ CAB average and not ~1.2...1.4m CAB average, then what is your idea? Somewhere in-between, or <1m? Intresting!
Thin in some places, fat in others.

For a second I thought you were describing me.

47
Arctic sea ice / Re: The 2019 melting season
« on: July 25, 2019, 01:51:03 AM »
The dipole has arrived. But it does not come with a lot of heat.

The SST's are very warm around the edges, but in no rush to invade the CAB.

2019 leads in some categories, but area losses are skipping, suggesting lost momentum.

The wind remains impressive, but mostly cold and pointed away from Fram. Some compaction, some dispersion, some export. Nothing record breaking.

The ice is in crap condition, but it won't disappear w/o good reason. Especially from the CAB.
 
I'm rooting for a record and anything else that might occur in the short term that will jolt the world ioward the necessary urgent response to AGW.

Second place doesn't make headlines. That where it looks like we're headed.

SSTs in the ice pack are buffered at 0°C or thereabouts by melting ice. You don't see the SST increase until all the ice is melted. You can't tell how much ice is melting by looking at SSTs until all the ice is gone.

48
Arctic sea ice / Re: "Stupid" Questions :o
« on: July 22, 2019, 12:18:20 AM »
It has been stated in the melting thread that there's a possibility of a huge high pressure ridge forming over the Arctic Ocean, and that if it happens it will be very bad for the ice.

But would a huge high pressure ridge be bad for ice retention, and why? Just because insolation is still high for a few more weeks? But wouldn't it also bring an end to the winds? Wouldn't big storms be worse?
BTW the same question you asked in the MST came to me the moment i was reading all the exited posts that, if it were mid june to mid july, were true, but people get used to keywords and key-events, often forgetting that the high season for a specific pattern is over or at least reduced and almost over.

Exactly.

I can't help but continuing to mull over the 2012 GAC, which exactly coincided with that year's 2D curves (extent, area) beginning to diverge from basically tied for lowest to way lower. I have read the objections about the GAC not being the main cause, but remain skeptical. It seems plausible to me that the worst thing for the ice this time of year (or at least in a couple weeks), now that the pack is fully mobile with plenty of warm water and air nearby, would be storms*. Yes, this is simplistic thinking and I'm no meteorologist, but on the other hand the "high pressure is bad" trope is no more sophisticated. Which is why I asked.

* Given a sufficient setup, which we seem to have this year as in 2012.



The earths outgoing energy (Wm2) on average is 239, so when the incoming radiation drops below that, you'd expect temperatures to drop and eventually for ice to form.
https://en.wikipedia.org/wiki/Earth's_energy_budget

It looks like the north pole drops below that sometime in late august. If you have less reflection from clouds in July it means that the ice and oceans are absorbing extra energy through insolation then they are losing. More energy = more ice melted.

In late July the energy absorbed is still as high as 60°N and almost as high as 30°N. That's pretty nice and toasty.

49
Arctic sea ice / Re: The 2019 melting season
« on: July 18, 2019, 07:53:14 PM »
The Coriolis effect tends to make the water flowing into the Arctic, from both the Atlantic and Bering strait, turn right. The warm water in the Bering strait goes into the Alaskan Coastal Current that flows eastwards on the north slope and may also go into eddies on the Chukchi shelf. In the fall the water may sink below fresher surface water forming the "summer water layer". This melting season heat stored from last year may be melting ice that has pushed from the CAA into the Beaufort sea.

You can see the mixing up of the summer water layer heat in recent buoy profiles from the Beaufort sea. That heat is helping to melt the thick multi-year ice imported from the CAA.

The extraordinarily warm water that we see now along the Alaskan coast will not directly affect the ice in the central Arctic but the heat will have indirect effects this year and next year. The continuing build up of heat in the Beaufort sea is leading to "Pacification" of the Alaskan side of the Arctic ocean and is playing a major role in multi-year sea ice decline.

http://psc.apl.washington.edu/HLD/Bstrait/BeringStraitSeasonalInterannualChange2017.html

Abstract 

Year-round in situ Bering Strait mooring data (1990-2015) document a long-term increase (~0.01Sv/yr whole record, ~0.02Sv since 2000) in the annual mean transport of Pacific waters into the Arctic.  Between 2002 and present (2015), all annual mean transports (except 2005 and 2012) are greater than the previously accepted climatology (~0.8Sv).  The record-length maximum (2014: 1.2�0.1Sv) is 70% higher record-length minimum (2001: 0.7�0.1Sv), corresponding to a ~1/4year reduction in the flushing time of the Chukchi Sea (to ~4.5months from ~7.5months).  The transport increase results from stronger northward flows (not fewer southward flow events); the velocity distribution's annual mode ranges from <25cm/s to >40cm/s, a 60% increase in speed and a 150% increase in kinetic energy, a metric which scales with the flow's impacts on bottom suspension, mixing and erosion. 


The Chuckchi sea's sea ice loss and resulting warmth may have profound effects, where the warm sea is warming the Beaufort gyres halocline, potentially slowing sea ice growth. We should worry if the Chukchi is above 13°C

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6114986/


The doubling of BG halocline heat content over the past three decades appears attributable to a warming of the source waters that ventilate the layer, where this warming is due to sea ice losses in the Chukchi Sea that leave the surface ocean more exposed to incoming solar radiation in summer. The effects of an efficient local ice-albedo feedback are thus not confined to the surface ocean/sea ice heat budget but, in addition, lead to increased heat accumulation in the ocean interior that has consequences far beyond the summer season. Strong stratification and weak mechanical mixing in the BG halocline ensure that significant summertime heat remains in the halocline through the winter.

With continued sea ice losses in the Chukchi Sea, additional heat may continue to be archived in the warm halocline. This underscores the far-reaching implications of changes to the dynamical ice-ocean system in the Chukchi Sea region. However, there is a limit to this: Once the source waters for the halocline become warm enough that their buoyancy is affected, ventilation can be shut off. Efficient summertime subduction relies on the lateral surface front in the NCS region between warm, salty water that is denser to the south and cooler, fresher water that is less dense to the north. For longer-duration solar warming (that is, longer-duration ice-free conditions in the region), SSTs on the south side of the front may become warm enough (around 13°C, under the assumption of a 1.5-month ice-free period dominated by solar absorption) that the lateral density gradient is eliminated [see (24)]. It remains to be seen how continued sea ice losses will fundamentally change the water column structure and dynamics of the Arctic halocline. In the coming years, however, excess BG halocline heat will give rise to enhanced upward heat fluxes year-round, creating compound effects on the system by slowing winter sea ice growth.


50
Arctic sea ice / Re: The 2019 melting season
« on: July 16, 2019, 05:57:56 PM »
Unless you are looking at good detailed nautical charts you have no idea how deep specific small areas of a sea floor are. Shoals and banks as well as rock outcrops can be a few feet below the surface of an otherwise deeper area of ocean. I have not seen on-line anything on ocean depth that gets down to a scale that would detail such small navigational hazards for the arctic, though I suspect they exist if I were to search hard enough to find them.

I guess Google Earth Ocean floor doesn't exist yet? ::) I found this map that's very detailed, but maybe not detailed enough? On this map I am seeing a few little islands, so you're probably right that this could be an island that doesn't rise above the ocean surface. I'm posting the link, because the image is quite large in size.

https://nik.bot.nu/o3129683.jpg

I'm trying to reply to Rod, but I keep getting this message.
The following error or errors occurred while posting this message:
The message body was left empty.

So what am I doing wrong?

I'll post my reply to Rod here...

Thanks Rod. And no, I've already made Neven mad this weekend when I was posting while drunk, so I'm gonna try not to repeat that.  ;) I need an app that blocks me from posting while drunk...  :-[  :-X Sorry about that post Neven!

Water is opaque to radio waves, the only way to accurately map the oceans is with sonar, and there hasn't been much of that in the Arctic. That's why other planets are better mapped than the earth.

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