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Andrew Xnn

Here is what the anomalies look like as of today:
June 30 2011 6z

Considering that we are looking at a ice/water mixture which isn't going to deviate much from freezing, it's somewhat exceptional to see such a large positive anomaly over the central basin. Far more common to see such positive anomalies when the average temperature is significantly below freezing.

Also, while missing the last 4 days may not make that much of a difference, it should probably not be ignored and comparisons between years should be consistent.

Still Neven, many thanks for putting up a great comparison of temperatures. With the right winds, 2011 can easily set all types of records.

Neven

Thanks, Andrew. In a couple of days I'll replace that image, once data until the end of the month has been processed.

Harvey Puca

The first oil tanker is heading out to China via the north east passage:

http://www.barentsobserver.com/seasons-first-oil-tanker-sails-northern-sea-route.4939088-116320.html

Bfraser

Yes, there's a mixture of ice and water, which is near freezing, but is that true of the baseline? In other words, I'm guessing that the baseline was solid ice at this time of the year (hence -4C).

Andrew Xnn

Here is a view of temperatures north of 80N for 1958:

and here is 2011:

Big difference between 1958 and 2011 for ice coverage, but the summer temperature ceiling looks to be about the same. After the melting point is reached, temperature rises are muted. Suspect the difference is dew point.

Images from the DMI site: http://ocean.dmi.dk/arctic/meant80n.uk.php

Rob Dekker

Great post again Neven !

Note that the nice clear weather from the past week(s) also occurs during the highest solar irradiance period. With clear skies, the SW (sunlight) input can be as high as 275 W/m^2. That's brutal.

Even conservative radiation balance calculations show that over ice, during this (end of June/start of July) SW input at clear skies should let the ice absorb some 50 W/m^2 of "melting power". That's enough to melt some 10 cm ice per day off the pack resulting in melting ponds and cracks opening quickly.

And open water (notably the Kara sea and the Chukchi sea) should absorb at least 200 W/m^2 over clear skies (due to the gap in albed) That's enough power to heat that water 1 C in one day, 4 meter deep. No wonder we see that water warm so fast.

Open skies right now are futile later on...

Patrice Pustavrh

Rob, I think you have missed a decimal point in stating in melting 10 cm per day (that would mean melting 3 m of ice per month, which obvious is not happening). Let me clear out:
50 W per m2 is good measure of energy absorbtion (500 W/m2 is actually little bit less than max solar insolation at NP during solstice). But that makes 50*24*3600 Joules of energy per day. Which is enough to melt about 12 kg of ice per day. But, 12 kg is not 12 cm, but 12 mm. Note that 1 kg is about 1 dm3 of ice. 1 dm 3 is 0,001 m3, which gives us at surface of 1 m3 0,001 m of height, which is 1 mm and not cm (which is 0,01 m). Anyway, I can agree with you that in areas with less than 50% of ice, melt and warming should be drastical, and increase of water temps can be easily addressed to sunlight warming.

Derek

While desperately trying to avoid the physics, the ice isnt just melting. Sublimation consumes a lot more energy than melting and the melt ponds will evaporate. This evaporation also takes more energy out of the system.

Artful Dodger

Derek: How has this energy left the system?

Rob Dekker

Thanks Derek. I always thought that at 0 C, very little energy goes to sublimation/evaporation versus simply melt, but I readily admit that I have not studied that at all. Do you have any info on that ?

Andyborst

Off topic for the blog. But I have noticed through the graphs page that Antarctic temperatures have been running hot for months now. Maybe this will strongly affect global sea ice anomalies and you will have to rename the blog, Neven :)

Neven

What can I say? Global Sea Ice blog does sound better. :-)

BTW, I don't know if the SATs have anything to do with it, but the anomaly for Antarctic sea ice area is anomalously low: -0.256 million square km.

If Arctic SIA keeps plummeting, things will get interesting at a very weird time.

Patrice Pustavrh

Derek, I do think that sublimation/evaporation is really non issue. Note first that for both effects, a molecule should have significally more energy to escape the ice/water than just to melt away (a few hundred times) and that the probability that molecule gets so much more energy is even smaller (note that probability decreases with difference from balance energy). And yet another effect, if evaporation or sublimation effect, the equilibrium point (e.g. 100% relative humidity is reached and the water in the air should start to condense and actually the energy lost would be returned back). I am just sorry, but it is about 20 years since I finished studying and doing physics (and I was never very strong in thermodynamics either) and I cannot provide you really correct application of physics required (and yes I sometimes just wish I would learn more, but, hey, I've been stuck with computer programming and it feels me good too. Darn, there is always so many interesting things to learn, and there are also so many other good things to do, and I sometimes I really wish I would have some more time, but anyway, it is exciting and I am very cool with that)

Janne Tuukkanen

During springtime in Nordics the sublimation effect is quite strong. If it rains, snow melts fast, of course. But if you get strong winds, snow packs will collapse also quickly, without any melt water at all. I live in mid-Sweden, and sometimes we get those weird Föhn winds from Norwegian mountains in middle of winter. Effect is astonishing.

Patrice Pustavrh

Well, Janne, I won't object your observations. But, comparing snow and ice is a tricky bussiness. Snow can be compacted by getting wetter a great deal (think of the nice powder some skiers really dream about, and that nice powder would collapse soon as it gets warmer - yes, snow can collapse and loose thickness a great deal. But, if you want to compare effect to ice loss, think about spring and effect of same winds to snow at that time - densities are much more similar and there is no way snow gets compacted much more). Anyway, thanks for sharing observations. But, I'll be glad if you tell me that rapid snow melts without ponds happen in late spring in Foehn effects or not, or if these effects are more significant during high winter.

Derek

I did a quick google search, as I dont know the answer.

http://www.ldeo.columbia.edu/res/div/ocp/pub/tremblay/amsbudget.pdf

"According to Dery and Yau (2002), the combination of surface and blowing snow sublimation (E +Qs) re-moves 122 mm a−1 swe (99 and 23 mm swe a−1 swe,respectively) or more than half of the annual precipitation falling over the Arctic Ocean."

I will admit to having not read the whole paper and have probably missed something.

Janne Tuukkanen

You are definitely right. Loss of snow depth is far greater than the loss of mass. I only argue that direct phase transition from ice crystals to water vapor is considerable, and something you should account for. On ice the strongest effect could be that snow over ice will come more compact, and lose its insulating effect.

Patrice Pustavrh

Janne, I could not agree more with your observation. You just added another piece to the great puzzle. And I personally do think that a melt water puddles and blueish hue of the ice in satellite images are just confirming what you have written :)

Patrice Pustavrh

UUfff.. I what really read what from Janne's post is what I wanted to see and not what he was saying. But, in fact, I do believe he has find me a great clue and a great connection. The warm winds can wreak havoc with ice covered with snow, as thinning it and allowing much more sunlight absorbtion and thus enhancing melt).
Well, I am remebrering Lodger's post from a year behind, and I was not so convinced about a bottom melt and sunlight absorbtion. Now, after year, I am more than sure his points were valid (and yet still cannot accept all of them, but, hey, I still have time either to make a valid argument against - which I haven't, or to accept his point's as valid - which I am close to, but yet, and without any valid scientific study, I just cannot be sure enough - except for having my mouth shut with an exception of personal aplogy, which, by the some mercy of innocent soul not knowing enough I am allowed to have).
Anyway, thank you Neven and all the contributors. What I really like about this blog is that it forces you to learn more.

Janne Tuukkanen

I've lived whole of my life in Nordics. And I thought that I knew enough about snow and ice as anyone. When I started to read Neven's, I realized I knew nothing. Especially salt water ice behaviour is something totally different from small lakes I'm used to.

But you know you're learning, when you understand how little you know.

Andrew Xnn

Sublimation is an important consideration for melting of ice & snow. I say this from experience.

Have noticed that in late winter/early spring as temperatures rise above freezing, that not much snow will melt as long as the dew point is below freezing. However, as the dew point rises above freezing, then the melting is much faster.

This is why temperatures in the arctic are not as important as the dew point.

During the summer, if the atmosphere is calm and clear, then temperatures can quickly rise above 0C. However, there won't be much melting if the dew point is still low. That's because there is so much evaporative cooling.

Derek

Artful Dodger "Derek: How has this energy left the system?"

Blowing in the wind, as humidity in the air, that once was ice.

Wayne Kernochan

Another delurk:
@andyborst - I had raised a similar point about high Antarctic temps early this month, and Gas Glo pointed out that (a) according to global warming theory the temps should be especially higher than normal during winter in polar regions, and (b) that those land temps remained below freezing, while sea temp anomalies nearby averaged zero anomalies, so there was no clear reason for Antarctic sea ice to melt unusually.

However, the pattern (admittedly, I have not been following it as long as I'd like) is even more puzzling. Last fall, Antarctic sea ice extent positive anomalies spiked to nearly record levels, while area anomalies were positive. The low area at minimum of Antarctic sea ice was back in 1993, iirc, although the low in 2011 was somewhat close. And, despite the fact that area in the Antarctic is close to its yearly maximum, the ice as shown by NSIDC appears unusually "pea soupy" (low concentration).

I have only a tentative explanation for this. Studies show that a warm underwater circumpolar current continues to move southward, and is affecting the latitude of Pine Island Glacier. Warmer than usual temps on land may be causing stronger than usual winds, which move the ice about faster and therefore both make it less concentrated or move it northwards to the point of melt, like a whirligig. Also, at the same time, the warm underwater current moving further south could be moving the ice faster from below, which could be causing the same effect. I am not really convinced of either explanation, since I don't see why the winds from the land should have that much effect on sea ice movement, and I find it hard to believe that current movement southward could have been that great.

However, I view the potential current movement, right now, as much more serious. What I believe we're all really worried about is the possibility that the loss of West Antarctic land ice will continue to accelerate. The recent studies suggest that the key to the process is the current eating away at the attachment of land glaciers to the ocean floor, resulting in much less "friction" as the land glaciers slide into the sea. If this is an indication that current movement is happening, we should perhaps expect stability or even further negativity in the anomalies as sea ice area in the Antarctic levels off at its maximum. And in that case, it may be that the combination of Arctic and Antarctic sea ice reaches its greatest anomaly ever (I believe -2.1 sq km) this month, and perhaps its lowest maximum ever in October.

Just some thoughts ...

Gas Glo

Artful Dodger "Derek: How has this energy left the system?"

Derek Moran "Blowing in the wind, as humidity in the air, that once was ice."

What happens to the water vapour? It rains out at some point. Perhaps it could have travelled out of the Arctic circle area before that happens but such air is likely replaced with other moist air. When it rains out, the energy is given up to the atmosphere and it is easier for the energy to be lost to space from there than from the ocean.

That loss of energy is subequent to condensation. The energy isn't lost through the process of evaporation or sublimation. The energy is still there just not as a temperature effect.

If the energy had remainer there as a temperature effect energy is slowly lost through warmer body radiating more energy. But which loses more energy? A slow loss over ~11 days that water remains in the air (or is average residence time different in Actic?) or avoiding that slow loss of energy but then getting a big hit though the temperature effect reappearing some time later possibly high in the atmosphere which is a good location for losing heat rapidly? ?o)

Derek

Gas Glo. Thanks for the clarification. I only really wanted to point out that sublimation did happen, rather than get too involved in the artic energy balance. As water moving from a solid to a gas requires a lot of enegy, then there is less available to just melt the ice.

As for evaporation from melt ponds? Is that happening here?

http://www.arctic.noaa.gov/latest/noaa1.jpg

The water in the ponds could be lower than the surface due to volume contraction when ice melts, water being more compact than ice?, lots of other reasons I cant comprehend.

Andrew Xnn

On the July 2nd image from NOAA1 cam of the arctic; the skys are mostly clear and there are sparkles in the snow. So, the snow is still crystalline and has not begin to transform significantly. Temps may be above freezing, however dew point is probably well below.

The albedo of snow will rise as it begins to melt and become saturated with water and less crystalline, but right now it is still fairly low.

Rob Dekker

Patrice, thanks for pointing out the calculation mistake I made. I simply missed one digit in the heat of fusion. I should have known better.

Either way, it turns out that the 50 W/m^2 for melting is ultra-conservative. Serreze et al 2007 mentions that the July net surface flux is 100 W/m^2 (towards melting and ocean heat gain). That means 2 mm/day average melt. If that's the average, then a clear day should cause even more heat to go to melting.

Here is a quick estimate of the 'upper' bound in early July : Clear day SW down flux 375 W/m^2, albedo of sea ice 0.6, gives heat absorption of some 225 W/m^2. That would be close to 5 mm ice melting per (clear) day. That makes more sense.

In fact, unusual number of clear sky days and associated high direct solar irradiance has been mentioned as a lead cause of the 2007 extreme extent loss. In 2010, bad weather at the end of July saved a repeat and probably new record setting.

I wonder if this year will show a similar July pattern as 2010, or if it will be more like 2007. If the latter, then, combined with the sharply reduced ice thickness (much less multi-year ice than in 2007), then 2011 minimum extent could easily drop far below 2007 record.

Rob Dekker

Sorry guys, I seem to be off with math these days. At 0.6 albedo and 375 W/m^2 SW input, 150 W/m^2 is absorbed.
Of course, that's not the whole picture and I'll do a bit more analysis on the exact numbers.
For one, we need to count in atmospheric energy transport (some 91 W/m^2 and IR balance) before claiming excessive melting amounts for clear days.

Arcticio

There is a heat flux variable within in the Global Forecasting System. The scripts to extract are here. The author states: "1 MJ/m² can melt about 3.25 mm ice"

Rob Dekker

Arcticio,
Thank you for posting this image !
I'll look through the details of the scripts in a bit, but for now, I think that this image also shows only a part of the overall heat flux picture on sea ice.

The fact that the surface heat flux over most of the Arctic Basin is close to zero suggests that flux does not include direct melting due to SW (solar) radiation.

I suspect that this image shows only the atmospheric (temperature) interaction with the sea ice, which would have to added to the direct melting by SW radiationa and local IR inbalance.

Patrice was right that 50 W/m^2 irradiance can melt 1 cm of ice per day. The Serreze et al's average irradiance of 100 W/m^2 would thus suggest 2 cm / day average July sea ice melt, and the upper bound for albedo-adjusted direct solar sea ice melt I calculated (150 W/m^2) would suggest melting of 3 cm/day directly over ice on a clear day.

This excersize (calculations and the GrADS scrip image) suggests that direct melt is predominant over the ice pack, while lateral heating (due to transport of warm air and ocean water) dominates melting at the edges of the pack.
Interesting stuff.

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