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Robert S

Looks to me like the extent maximum may be in. As you say, Neven, the game now is all about snow cover and melt season dynamics. Going to be interesting.

Rob Dekker

Very nice update, Neven, thank you !

Regarding that PIOMAS-CryoSat divergence issue, Your theory makes a lot of sense ; that thick snow cover may fool the Cryosat freeboard measurements into believing there is thicker ice (and thus more volume) than there really. If so, PIOMAS is likely more accurate than Cryosat for years when there is a lot of snow on the ice.

However, just yesterday I read this paper :

They note that is snow load on the ice is so large that the weight of the snow pushes the ice under the water level, then sea water will creep into the snow and form what they call snow-ice. The snow layer does not get thinker after that, since for every kg of snow that falls, an almost equal amount of snow-ice will be formed.

They note that this effect of snow-ice formation occurs with heavy snowfall, and is actually the main reason of ice formation over second-year ice,

If the PIOMAS does not account for that effect (of snow-ice formation under snow), then it may actually be Crysat that is more accurate.

Something to keep in mind.

the weight of the snow pushes the ice under the water level

This is actually the normal in the Antarctic (as the paper you linked to mentions), and not so often, perhaps rarely, in the North.

If the PIOMAS does not account for that effect (of snow-ice formation under snow), then it may actually be Crysat that is more accurate.

Assuming that Cryosat under such circumstances has any accuracy left.

I have always suspected that the reason Cryosat never (AFAIK) showed any analysis for the Antarctic was just this fact.


Thanks for that paper, Rob. I didn't know about snow-ice formation, although I have often wondered about what goes on where the snow touches the ice.

John Christensen

On snow-ice,

It would appear that DMI's polar portal ( http://polarportal.dk/havis-og-isbjerge/havisens-tykkelse-og-volumen/ ) also does not recognize the snow-ice formation, as February volume growth was low, even with decline towards end of the month.

However, for March with lower temps in the central Arctic basin, DMI's volume measure has gone up again, maybe due to snow-ice turning into a more solid state?

Historically on snow-ice: Even the accounts of the Fram voyage 1893-96 mentions examples of ice being submerged by snow, but also that it was rare and that winters were dominated by high pressure, dry climate, less wind and ice primarily being formed due to pressure ridges and in open lanes.

Clueless FM

Eric Holthaus eating some delicious winter max crow today, while pondering whether or not to appear as a guest star on his own ‘Warm Regards’ Green BAU–sponsored climate podcast for the first time in 2018, and, looking back through his archives, for the first time since October 2017. So he’s been on holiday / sick leave for a full five months.


The part about the max crow is funny, because the max is notoriously deceptive and hard to call. You could've left out the rest. Eric Holthaus is a great climate journalist.

Robert S

One effect of increased (but still below freezing) Arctic temperatures that I hadn't considered before was the amount of sublimation from snow. A good study of these effects (https://www.igsoc.org/annals/49/a49a050.pdf) shows that there is a significant increase in sublimation rates with increased temperature, as well as with increased wind. These effects will both result in snow mass loss, but also in crystal structure change within the snow, which will interact with the snow ice formation process discussed above. I don't know how much models like PIOMAS take sublimation into account.

Robert S

Sorry, the reference should be https://www.igsoc.org/annals/49/a49a050.pdf


Indeed Robert !

How about Gigatonnes??

"Overall, our results show that the 2006–2016 Antarctica average integrated blowing snow sublimation is about 393 ± 196 Gt yr−1, which is considerably larger than previous model-derived estimates. "

"Blowing snow sublimation and transport over Antarctica from 11 years of CALIPSO observations (PDF Download Available). Available from: https://www.researchgate.net/publication/320994814_Blowing_snow_sublimation_and_transport_over_Antarctica_from_11_years_of_CALIPSO_observations [accessed Mar 13 2018]."

Note figure 4 sublimation below -30 C.

"For the same time period, our computed CALIPSO based average blowing snow sublimation is about 50 mm yr−1. This means that on average, over one-third of the snow that falls over Antarctica is lost to sublimation through the blowing snow process. "

In a practical sense the greater the winds the more snow sublimates....

Robert S

Makes sense, Wayne. So the variables in the sublimation equation will be temperature, wind speed, and probably snow compaction/cementation (i.e. snow doesn't blow as much because it is cemented). Temperature will have both + and - impacts, since internal sublimation and recrystalization, resulting in more cemented snow layers, will occur faster at higher temperatures up to some temperature. Growing up in Saskatchewan I've certainly seen that effect at work! It'd be interesting to know how this theoretical equation would interact with the expected impacts of global warming in the arctic.

John Christensen

Back to Arctic temps:

Interesting to see how the recent SSW event caused a subsequent stabilization of the Arctic vortex with a stable central Arctic high and DMI 80N reaching seasonable levels for the first time in many months:


If my memory serves me right we saw a similar return to stable cold Arctic temps in early 2013 following another significant SSW event.


Correct Robert

As spring progresses top of snow hardens and shines with frozen water vapor from sublimation...

A couple of important events are occurring, I believe a strong La-Nina is in the cards again, Arctic Ocean Atmosphere is finally "drying" out, as we can see with satellite pictures enormous leads spanning great distances.

First Melt, an exotic refraction optical effect occurred on the 14th, repeated on the 20th with quite a showing of persistence, principally meaning the sea ice is very thin :


The earliest date for First Melt in history (2010-2018) could not have come without a much warmer and moist Arctic atmosphere throughout winter, I expand on this clear air moisture topic with an article called:



Worldview seems to show a fairly shattered Atlantic side and Beaufort Gyre that's already in action.

I say this year is going to be bad!

John Christensen

For an early prediction of the coming melt season, I would see 2018 as a continuation of recent relatively low-melt seasons, due to:

1. NH hemisphere continents (Especially Alaska and Siberia) are heating up quickly

2. Significant cold (-25C and lower) area is confined to northern Greenland, CAA, Siberian coastline and the Arctic Ocean:


3. We have at least 1000km3 more sea ice within the same area compared to last year due to thicker sea ice cover in the Arctic Ocean:


These factors all indicate a high difference between the rising temps on the continents against the cold Arctic Ocean, which tends to increase occurrence of summertime quasi-constant lows over the AO.

Susan Anderson

For anyone making predictions based on current events, I'd recommend waiting a couple more weeks for all traces of the recent SSW (Sudden Stratospheric Warming) event to be assimilated into the global system. It has, in my amateur opinion (based on an inadequate sample, which is why scientists are not committing), caused a lot of cold weather in Europe and the US (and possibly elsewhere, I wouldn't have any direct knowledge about that) when it's occured in the past few years. While I know we all know that weather is local and climate about global weather trends over time, it's impossible not to view climate through the lens of local weather. I'm not suggesting we are incapable of objectivity, only that we are human!

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