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Messages - RoxTheGeologist

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1
Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: June 19, 2020, 06:31:32 PM »
Area Graphs for the High Arctic Seas from NSIDC Data

Chukchi - after a late start area at 2010's average.
Beaufort - also a late start & area well above 2010's averge.
CAA - also late start at close to 2010's average and about to hit the elbow (someone remind me why this happens?)

Two distinct areas of melt with very different timing?

2
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.



3
Arctic sea ice / Re: The 2020 melting season
« on: May 28, 2020, 05:14:40 PM »
Lowered albedo does increase short wave solar absorption, but also long-wave earth radiation. Since in the winter the latter predominates and in the summer the former, they must be roughly equal somewhere, probably mid-May. Likewise aerosols both cool and warm. As anyone who has had a garden knows, the first frost is on a cloudless night. People seem to be writing about only half of the effects of these phenomena.

I'm not sure I read this correctly; note that emissivity is controlled by temperature and not by colour. Just because something is dark doesn't mean it will emit more radiation. Colour is largely controlled by how the object reflects visible light (unless the object is hot enough to emit light in the visible spectrum). The two properties are unrelated.


4
Arctic sea ice / Re: The 2020 melting season
« on: May 16, 2020, 01:40:03 AM »

...
Is this normal? ...

Perhaps the reduced aerosols are contributing to the reduced cloud cover more than would be expected.  I don't know much about the specifics there but maybe the relationship between aerosol density and cloud formation isn't linear or continuous.
I would think that besides the ~1/3 reduction in global aerosols (I could be grossly off o this # but I think it is reasonable), the 90% drop in air traffic is the biggest contributor to the lack of clouds. Or, the drop in air traffic at this point may be taking primacy even over the drop in aerosols. There was a study after 9/11 that showed a major rise in temperatures when air traffic halted. This is now being replicated much more severely across the entire planet.

Contrails are thought to have a net warming effect, particularly as they form more readily at night rather than day. Clouds keep the planet warm.

https://journals.ametsoc.org/doi/full/10.1175/JCLI-D-19-0467.1

" In contrast, the level of understanding for contrail cirrus impact has been thoroughly upgraded during the last 10 years, and it is currently considered as the largest component contributing to aircraft-induced radiative forcing (Burkhardt and Kärcher 2011; Schumann and Graf 2013; Bock and Burkhardt 2016b; Grewe et al. 2017)."

5
Science / Re: Contrails & artificial clouds
« on: April 28, 2020, 08:58:10 PM »

Contrail cirrus is an interesting problem. Soot from contrails can produce more and wider cloud, and it's particularly prevalent in cooler air.

Current LCA models do not allow for contrail cirrus. If they did they are estimated to increase the GWP 2x to 4x the amount of other emissions.

Contrails act to warm the earth, not cool it.

6
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.


7
Antarctica / Re: PIG has calved
« on: February 11, 2020, 08:02:49 PM »
The relative size of the ice to the water it needs to displace is significant.

Eureka.
The water you need to displace is one to one to the volume of ice under the water. Same mass according to Archimedes.
You would also see significant eddying around the perimeters if the forces of tension from the calving were responsible for the movement. I see mostly  uniform movement rather than the chaos you would expect from internal forces acting at different vectors.


If a 100km iceberg moves 10km, how much water is displaced relative to the size/mass of the ice?  Not 100%!

100% of the mass if the ice is floating, size wise its Volume*(density of freshwater)/(density of seawater).


8
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.


9
Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: February 01, 2020, 01:03:36 AM »

That's what's meant by 'blast past'?

I'm sure he meant February...

10
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.

11
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....

12
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.

13
Antarctica / Re: PIG has calved
« on: January 25, 2020, 06:10:49 PM »
Confirmation from Sentinel-1 that the tip fell off.

That's just the tip of the iceberg from the upcoming calving.

(Sorry. I'm a Dad.)

14
Arctic sea ice / Re: The 2019/2020 freezing season
« on: January 25, 2020, 06:08:22 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.

My guess is that, based on my understanding of thermodynamics, more heat is lost in areas with combinations of highest temperature and lowest relative humidity (e.g. deserts, which typically have the highest spread between high and low temperatures on any given day). In such areas there is the greatest differential between the heat source (earth) and heat sink (outer space), coupled with the lowest combination of greenhouse gases (water being by far the most important).

If the poles were the only places to lose heat then nights wouldn't be cooler than days anywhere except the poles. All the surface of Earth is losing heat all the time, more rapidly where the Earth is warmer.

To illustrate FTBs point: From Wikipedia - on diurnal temperature ranges:

...diurnal temperature variations typically range from 10 or fewer degrees in humid, tropical areas, to 40-50 degrees in higher-elevation, arid to semi-arid areas, such as parts of the U.S. Western states' Intermountain Plateau areas...

Illustrating how daytime heating from insolation is lost to space, and how humidity (water vapor acting as a GHG) slows down that heat loss.


15
Arctic sea ice / Re: MOSAiC news
« on: January 21, 2020, 06:51:55 PM »
Close up on 2019O4 ctr
Added overview of temperature at 100m and whoi itp102 profile contours. cffr

Why is the salinity decreasing with time? The thickness of the low salinity layer is increasing - I'm going to assume that the ice is thickening and expelling brine so I'd expect the salinity of the water below the ice to increase. Am I missing something obvious? Does it take all year for freshwater input from the rivers to reach equilibrium under the ice?

16
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.

17
Antarctica / Re: PIG has calved
« on: January 14, 2020, 06:50:10 PM »

Seriously. I check this thread every day. it's a real (ice) cliff hanger.

18
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.

19
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.

20
Arctic sea ice / Re: The 2019/2020 freezing season
« on: January 08, 2020, 05:53:02 PM »
Great animation!

I'm still wondering what has changed to increase the ice in the Barent Sea over the last year. For the previous few of years it barely made it over the Nansen Basin continental shelf with incursions up the St Anna Trough. This year it's filling up the sea between FJL and Svalbard.

Is this a worrying indication of less heat transport from a slowing AMOC? Nothing else seems to have changed.

21
Arctic sea ice / Re: The 2019/2020 freezing season
« on: January 07, 2020, 06:24:12 PM »
If warmth can't enter the Arctic Ocean through the Strait then at other times cold can't exit the Arctic into the North Pacific. The Bering Sea would likely heat up even faster - perhaps large parts of Alaska and far East Russia too, accelerating permafrost melt and thus methane and CO2 emissions.

I actually think that by stopping hot water to enter from the Bering sea, that the cooling of the Arctic would help to protect the permafrost.

The flow of the water is always into the Arctic ocean, and so no cold water ever flows from the Arctic Ocean into the Bering Sea, unless there is a southern wind. (this needs a fact check) So by stopping hot water to enter the Arctic, you keep it cool, which will help to keep our planet cool.

AGW will indeed still continue. It needs to be stopped. But maybe we can stop a disaster by doing this. It's cheap, easy, and low impact on marine life IMHO. Although I'm sure a lot more educated people than me will have something to say about this...

Blocking the Bering is more akin to putting a blanket over your air conditioner heat exchanger, rather than closing your fridge door. The AC heat exchanger gets really cold: The rest of the room heats up until equilibrium is reached.

22
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?

23
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?

24
Arctic sea ice / Re: The 2019/2020 freezing season
« on: October 27, 2019, 09:53:24 PM »
A Polar Vortex Split is coming in about a week.
This is again, very bad news, coming earlier Year by Year.
The Oceans are just spewing out Heat, relentlessly.

Why is the release of heat a bad thing since it can now radiate back into outer space? I am confused when the complaint is that heat is being trapped in the ocean and also when heat is not being trapped. I just want consistency.

Yup, it's better to release that heat. I guess the worse conditions for ice formation are a good thing when the energy balance is for heat loss. It's a worrying feeling though, hoping for less ice so the Earth can lose its excess heat. The problem is that the ocean just shouldn't be that warm.

25
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).


 

26
Arctic sea ice / Re: The 2019/2020 freezing season
« on: October 24, 2019, 10:29:35 PM »

I think I'm missing the point. I'll try stating this in a different way to try and understand.

If there is, say, typically, 0.5m of ice, then there is less transmission of heat out of the ocean to the atmosphere because of the ice's insulating properties. If there is no ice, the ocean heat can freely escape to the atmosphere. If there is more heat coming out of the ocean the air will be warmer than over sea ice. It doesn't take much of a drop in water temperature to warm the air to the same temp. Of course, there may well be more water vapor to trap heat from the ocean, but that would also correlate with lack of ice, as one would expect both the temp and the frost point to be higher than average.


27
Arctic sea ice / Re: "Stupid" Questions :o
« on: October 24, 2019, 10:00:19 PM »
Have you all forgot the basics of sea ice formation? RoxTheGeologids, macid, slow wing?

Sea ice is densest at freezing point, and thus does not freeze in the same way that lake ice does. So slow wings "model" is patently wrong, and the increased density of surface waters as they cool and sink create enough convection to stir up the top tens of meters of ocean, getting all that heat to the surface.

Which is not to say that wave action will also create turbulence.

The current ice-free areas have a fair amount of wind according to NullSchool, but more importantly, the air temps are nowhere near low enough to start freezing.

I think that's what I said. I don't understand where I went wrong with my statement. Please edify!

28
Arctic sea ice / Re: The 2019/2020 freezing season
« on: October 24, 2019, 08:56:40 PM »
I think the corresponding shape of ice-covered areas on the one hand and higher surface temperature anomalies on the other hand can be easily explained. If in the long term (e.g. median 1981-2010) a certain area of the Arctic Ocean has been usually covered with ice at a certain date and this year it is not, the difference in surface temperature (ice-covered = well below - 2°C; ice-free = above -1.8°C, maybe above 0°C) must be clearly visible in the SST anomaly map.

Exactly. That's a much better explanation than I gave. The air has a much lower specific heat capacity than water, so water is the temperature 'buffer'. Once ice forms the ocean can no longer transfer heat to the air as effectively, and the temperatures will tend to the long term average.
 

29
Arctic sea ice / Re: The 2019/2020 freezing season
« on: October 24, 2019, 06:43:18 PM »
I suggest that no matter how we got here, there is a connection between
- where the ice is and is not,
- SST anomalies,
- Surface temperature anomalies.

Warm water stops the ice forming and heats up the air... if the air warn't warm then, I guess, the ocean wouldn't be losing heat....

30
Arctic sea ice / Re: The 2019/2020 freezing season
« on: October 24, 2019, 05:36:04 PM »
Forum members will recall that earlier this year the discussion was largely about conditioning the ice. In particular heat transfer from water vapor just above the ice was seen as key to creating melt ponds that would drive melt. Low humidity, clear skies would not do this.  Solar energy impacting the system was not seen as a key driver of sea ice melt.

Thus, when significant low humidity clear skies occurred over substantial areas in the arctic basin many predicted a non record breaking melt. Which is exactly what transpired.

But what is the significance of the heat that entered the Arctic Sea system?  Is this added energy now affecting the re-freeze?

I thought that the discussion was around this hypothesis; cloudy weather reduces heat loss and/or increases melting until around mid may depending on latitude. As the days lengthen insolation becomes the main source of heat and clearer days would transfer more heat to the ice. Melt ponds are the first indicator of  melting, and dramatically reduce albedo. I don't recall individuals saying clear skies would reduce ice melt in the high insolation months.

More heat in the ocean from decreased ice cover will slow down refreeze, particularly if that heat has been mixed in at depth. Cooling the surface water will induce convection if the salinity profile allows. However, a slow refreeze would be better in many ways for cooling the earth. When the ice forms it will insulate the mixed layer. Surface temperatures will fall further, because less heat is being transferred to the atmosphere from the ocean; it traps more heat in the ocean, and, presumably, slows down ice thickening. Putting a layer of insulation between the relatively warm ocean and the very cold Arctic night is not conducive to cooling the ocean

The best analogy I can think of is coffee, Putting a thin lid on it is a VERY effective way of stopping it cooling, as long as the lid doesn't melt, which makes the whole analogy rather disappointing for coffee drinkers.




31
Arctic sea ice / Re: "Stupid" Questions :o
« on: October 22, 2019, 06:46:10 PM »
Good questions, thank you Macid.

...

The background to my post above has been the common narrative on this forum that excess heat gets stored in the water column over the course of the melt season, together with the assertion that the refreeze cannot proceed to any great extent until that excess heat has first been removed by extraction to the atmosphere.

I've never been comfortable with that explanation because, given the situation of relatively calm water, I can't see how that trapped heat -- which I presumed to extend down by at least several meters and probably tens of meters or more, depending on whether it was sourced from ocean currents or direct sunlight -- can get to the surface to influence the refreeze.
....


As ice forms the ice is fresher than the seawater, the salts partitioning into the water. The denser cold, salty water sinks, creating convection. This causes the upper mixed layer to, well, mix, and deepen.  My guess is that it slows down the ice formation, but the mechanism needs ice to be growing before heat starts to move up from deeper layers.

I hope that the current expedition will show how this happens in real time! It's a really interesting theory.. lets see if the real world works that way.




32

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.

33
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?



34
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: October 22, 2019, 05:33:24 PM »
And, as if by magic, the Siberian seas freeze. The ESS is late this year, it typically freezes over very quickly. I wonder if there will be a pause as there was in 2016, or it'll be super fast like 2012. My guess is the former. In 2012 some of the heat had been sucked out of the mixed layer by the GAC. In 2019? I'd take odds (not very good odds though, it is the Arctic) that there is enough heat in the upper layers of the ocean to slow down refreeze, particularly over the deeper parts of the sea.

35
Arctic sea ice / Re: The 2019/2020 freezing season
« on: October 18, 2019, 12:06:59 AM »
In the last week or so....
- The Central Arctic Sea (North of 80) is freezing quickly,
- Most other seas are freezing very slowly,

Perhaps the persistent high +ve SSTs and the Arctic temperature anomalies (-ve near the pole, mostly +ve or very +ve elsewhere) have something to do with it.

Click gif to start - repeats 4 times

The arctic temperature anomalies are more likely the result of the SSTs, not causing them. water has a vastly larger specific heat capacity than air.

36
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.

37
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: October 10, 2019, 06:32:54 PM »
It's going to be interesting to see the effect that the open water is going to have on the weather in the North over the next few weeks/months.

For the first time in a number of years, we're seeing a 'normal' start to our cold season where I live.   Although it's still disgustingly more humid than it used to be.   A wet cold is nastier than a dry cold.  :(

Where are you?

38
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...






39

The vast majority of the continent has experienced no net change in ice.  All the melt is concentration on a small section along the western coastline.  The ice rebound is likely to be  less than 10%, as so little area is affected.

First, the 10% increase in ice mass loss, calculated based on GRACE satellite data, only applies to the WAIS and not to the EAIS.


Note also that there has to be corresponding reduction in height in from surrounding areas. The location and amount depending on the viscosity and topography of the asthenosphere. I don't see where the rock is coming from mentioned in the paper (my guess is along the rift axis). If the grounding line is the point of the most ice loss, then i would think that it would act to increase the angle of slope to the interior as that is proportionally pushed down. The wavelength of any elastic response is short in rift zones as the lithosphere is elastically weak, on the orders of 5-20 kms. Uplift of the grounding line coupled with decreasing bedrock elevation in the interior does not sound like a recipe for stabilizing West Antarctica to me.

40
Arctic sea ice / Re: MOSAiC news
« on: October 07, 2019, 06:24:10 PM »

I find the water temp line very satisfying for some reason. It's good to know the universe is working as intended.

Thank you A-Team and Uniquorn. It's going to be a very exciting winter for all scientists, including those of us firmly seated in our armchairs.



41
Arctic sea ice / Re: The 2019/2020 freezing season
« on: October 02, 2019, 04:50:32 AM »

The ice extent reaching Svalbard after a few years of it melting out, even in winter, suggests a change in where the warm currents are going rather than variations in wind direction. Perhaps it's some oscillation in the turbulent mixing that goes on in the Fram Strait. My own theory is that the warm water has to go somewhere, and my guess is to the north coast of Greenland and from there to the Nares strait. It'll be interesting to see if the Nares stays open all year.

42
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


43
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.

44
Arctic sea ice / Re: Accuracy of poll predictions
« on: September 23, 2019, 11:08:52 PM »

My typical method is to pick the bin above the median.




45
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

46
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.

47
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.

48
Permafrost / Re: Northern Hemisphere Winter 2019-2020 Snowcover / Misc Obs
« on: September 18, 2019, 06:48:46 PM »

Hmm... Won't snow act to trap heat in the ground? I think the best analogy is when you burn yourself. The first thing you want to do is run lots of cold water over the burn.

Heat flow of a spike on the surface (say summer insolation) is best reduced by applying lots of cold to the the surface as quickly and for as long as possible. Having a nice snow cover reduces the heat loss dramatically compared to emissive heat loss from the ground itself. You have to conduct that heat through all those nice insulating air bubbles in the snow rather than just through a couple of meters of soggy ground.

Of course it depends on the timing, but I think there would be a good thermodynamic argument that deep and early snow cover is really bad for permafrost and sea ice retention. Snow on sea ice effectively reduces the FDDs buy elevating the temperature of the ice compared to having no snow. That snow cover persisting into the high insolation months has the opposite effect. Raising albedo when the sun should be warming the ground has the opposite effect.

As the Earth warms, perhaps we will go through a phase of increased snowfall as the amount of water in the atmosphere increases, but that snow will melt out faster in the spring. The worst of both worlds for ice and permafrost.

49
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.

50
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.



 

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