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Peter Ellis

The Maslanik image shows that Most of the "extra" MYI in the ASCAT radar images is second-year ice, which is sometimes classified as "perennial" ice instead of MYI. That seems to be the simplest and most logical explanation for the AARI/Comiso maps. They align quite nicely with the green pixels (and not the cyan ones).


Yes, that could also be it, Peter. A matter of definition.

One thing is certain: that ice looks less white than the rest of the MYI, and so shouldn't be as thick.


Another matter of definions. SST is widely interpreted as sea surface temperature but it might more properly refer to surface skin temperature esp if you are getting temperatures for sea ice covered areas.

(As there don't appear to be temperatures for land, perhaps this is sea skin temperature though I have never heard of that term.)

Chris Biscan

Those bottom maps are a joke and are embarrassing that they are put out.

Cryosat, air borne data, in situ measurements, piomas were all far thinner in April of 2011, and it's not even close.

I am sure it's much of the same. And for being thicker this season so far we have this from the Beaufort region:

ITP56 was deployed on a 1.5 m thick icefloe in the Transpolar Drift on April 15, 2012 at 89° 19.5 N, 1° 54.8 E as part of the North Pole Environmental Observatory (NPEO) . On the same icefloe, a Naval Postgraduate School Arctic Ocean Flux Buoy (AOFB), an US Army Cold Regions Research and Engineering Laboratory (CRREL) Ice Mass Balance Buoy , and an US-IABP Polar Area Weather Station (PAWS) were deployed. The ITP is operating on a fast sampling schedule of 4 one-way profiles between 7 and 760 m depth each day.

ITP63 was deployed on a 1.27 m thick icefloe in the Canada Basin on April 20, 2012 at 83° 26.9 N, 115° 50.0 W at the Russian NP-39 drifting ice station. The ITP is operating on a fast sampling schedule of 4 one-way profiles between 7 and 510 m depth each day.


ID Code: 300034012994830
Date: April 12, 2012 - Present
Type: First year ice
Initial Location: Beaufort Sea
Deployment: SIZONET
Co-located Instruments:

Initial ice thickness: 153 cm
Initial snow depth: 25 cm

Last Buoy Data:
Iridium ID: 994830

Lat: 71.511 deg
Lon: -154.690 deg
Air Temp: -14.86 C
Air Pres: 1020.90 mb

I dunno, it doesn't look to good. But we will see, HP patterns already taking hold and continue to show up on long term models.


crandles: As there don't appear to be [surface] temperatures for land

They do exist and are similarly called LST, Land Surface Temperature.

The are easily measured by the infrared instruments on weather satellites, provide there are no clouds.


Aaron Lewis

Ice thickness is not what counts. What counts is ice mass and ice temperature. Porous ice tends to float higher and look thicker to an eye in the sky.

I think we are at the point where the bulk of the sea ice is at or near its melting point, and much of the ice is so porous and weak that any wind moves it. A feedbace is that it floats higher with less mechanical strength, and tends to get blown around more. This results in internal work that adds energy to the volume of the ice. Such heat is only slowly convected to the surface in the winter. In the winter a thin (1.5 meter) surface layer cools, but ice is not a very good conductor. The porousity of the bulk ice also allows melt water and condensate to rapidly advect heat into the volume of the ice. Such ice with wind, waves and tides, tends to back-fill any areas that melt. This spreads the ice out and allows faster melt. The ice is floating in and over warmer water. And, heat has been advected into its volume during the last few melt seasons. Thus, after a few years, there is “multi-year ice”, that is no better than first year ice. This is a new state of things. It looks to the eyes in the sky that there is more ice. The truth is that the ice has gained heat, and lost bulk density.

Thus, for the next while, we will see high numbers for ice area, followed by an astonishingly abrupt melt off.


Hi Aaron

I completely agree with your conclusions. When the (summer)ice disappear it will more or less happen over nite, and even the so called experts will be surprised.

Regards Espen

Hans Verbeek

SST in the Northern Pacific is colder than normal for the end of april.

Good news in my opninion.

Arctic seaice extent is still very close to the normal for 1979 - 2000

Bob Wallace

Extent is only a two dimensional measurement of a three dimensional entity, Hans.

The small fish pond outside my window reaches 100% extent several times every winter. It does not develop enough thickness to survive the next warm day.

Patrice Monroe Pustavrh

Hans: That same reasoning was heard in 2010, when extent at some point in April reached "almost normal" values. But, as it showed up in 2010, the extent quickly decreased that year. Late freeze up usually means early melt down. And in April, there is much more variability. As Bob has explained to you: Extent does not show you everything. Pretty normal would be reached when throughout the couple (meaning at least five or even more) of years, we would measure normal extent/area. Which I seriously doubt it will happen.


I think it is worth noting how even the most simple of predictions can be confounded by the behaviour of the sea-ice.

For example, at the beginning of this month I would have expected relatively rapid sea-ice retreat on the Atlantic side, particularly behind Novaya Zemlya - where the ice formed relatively late and sea surface temperatures are high.

Instead, during April the ice has retreated quite rapidly from the Pacific side, where SSTs are anomalously cold, yet the sea-ice anomaly in the Bering sea has halved, while there has been little change in sea-ice in the Barentsz and Kara seas.

All this is a roundabout way of saying that I am not so confident in the assertion

a conclusion that was reached a while back already: sea ice on the Atlantic side of the Arctic looks vulnerable, sea ice on the Pacific side should be thicker.
I am not so sure! All I am willing to say with certainty is that there is a greater than 50% chance of there being less sea-ice this summer than last year, because of the long-term decline.


Misfratz, with 'sea ice on the Pacific side that should be thicker' I'm mostly referring to the Chukchi and Beaufort Seas (maybe I should be more sPacific wrt the Pacific ;-) ). On top of that, the relatively large amount of ice in the Bering Sea could act as a small barrier. But I agree, it seems to be vanishing fast.

Right now, I'd like to see what PIOMAS will have to say in a couple of days. Will volume still be the same as last year, or more, or less?


Misfratz the temperatures in the SOO and Bering sea have been warm during April. the kind of temperatures that melt ice while the Kara sea has not been that warm and is further north. Things appear to be happening pretty much as one would expect. South Kara sea has fresh very thin ice near the coast and the whole of the south Kara is going to start melting very soon. when that happens the extent will drop like a stone.
Greenland sea is doing what one would expect with a thinner more mobile pack and stays at a high extent. the Barentsz costal ice has melted off and the northern Barentsz ice is being topped up from the movement of ice from the central arctic. All very normal and predictable.
the Bering sea and SOO ice still visible is very shattered and thin looking for the most part. huge extent drops on the way in May.


"Arctic seaice extent is still very close to the normal for 1979 - 2000"

Hans Verbeek ther is a huge difference between the meanings of average and normal.

the size of the average woman in the UK is now close to being clinically obese. welcome to a new "normal". the reality of course is that the new normal is fat.
the same applies in the artic.

To suggest that the average figure represents normal is suspect.

Even if this year is close to but below being average then it is still in the bottom 50% of all years included in the average.
there appear to be 1-2 million square kilomeres of ultra thin ice spread around the arctic. nominally first year ice but in truth only days or weeks old. there is your illusion of extent. And that will vanish in the Arctic sun.


Philiponfire - What makes you say that the temperatures in the Bering sea have been warm during April? I'm looking at the anomalies on the OSTIA SST analysis, and all I see is a ribbon of large negative anomalies where the sea-ice edge is further south than normal, and a larger area of ~1K negative anomalies further south. See: http://ghrsst-pp.metoffice.com/pages/latest_analysis/sst_monitor/ostia/anom_plot.html?i=17&j=2


Misfratz, I think Philiponfire is referring to air temps. See here for the last week.

South Kara sea has fresh very thin ice near the coast and the whole of the south Kara is going to start melting very soon. when that happens the extent will drop like a stone.

Yes, SIA is artifically high there because open water is till freezing over. As soon as temps go up, SIA and SIE will drop very fast for a couple of days.


Ah, thanks Neven, and my apologies to Philiponfire.

Naively I would have expected that surface air temperatures would follow the ice edge and sea surface temperatures quite closely, because of the larger heat capacity of the ocean, and the energy required to melt ice, but there are some fairly large differences.

Kevin McKinney

"...during April the ice has retreated quite rapidly from the Pacific side, where SSTs are anomalously cold..."

Just a thought, but this makes sense if you turn the causality around. In other words, rather than be surprised that there's rapid retreat where low SSTs would not be expected to cause it, one might say, "Aha! The retreating ice is leaving cold meltwater in its 'wake.' That makes sense."

I don't know if that's what's actually happening in situ, mind you, but it would be logical. Melting soaks up a lot of heat, as we all know.

Chris Biscan

The Bering sun is high.

On top of that the last time the sia was that high in the bering CO2 ppm were in the 340s, its at 395 now.

This is far to often overlooked.

Al Rodger

Kevin. Re Low SSts.
The SST anomalies in the Bering/Okhotsk Sea area were dropping well before the melt started so the cold is from something else. It's actually been the coldest start to the year for those SSTs since before 1981 when the NOAA OISSTA data started, something which took my interest.
I was just messing with the data to see if it matched any phenomenon that I had data for & I think the PDO looks a likely suspect although it goes a bit odd in places. (The odd bits are a bit off to be volcano events.)
I post a temporary graph to illustrate the point.
Graph of SSTs North Pacific.


That's an interesting graph, Al, thanks a lot. I wonder if there will be an effect when the PDO reaches the heights it did in the 80's and 90's.

Nick Barnes

OT, really, but on the subject of ice movement, I see from recent MODIS that the ice is moving away from the NW archipelago coast in a really striking way.


Nick, my answer wrt the movement itself is in the ASI update thread.

With regards to the winter analysis: It looks quite spectacular, but does it mean anything with regards to the ice thickness there? Should ice let itself be moved so willingly, or is this normal?





not exactly tropical I know. but not cold enough to keep freezing the sea.

Michael Fliss

Nick, Neven: That lead off Banks Island is part of the Circumpolar Flaw Lead System that is recurrent. The U of Manitoba has studied it and the following article has a good map of the lead system and polynyas in the northern hemisphere where one might begin to look for the expansion of openings in the ice:


This is a link to the Centre for Earth Observation Science at the U of M and the studies that were conducted:



Circumpolar Flaw Lead System...

Sounds good to me!

Rob Dekker

Neven said :

How thick is the ice on the North American and Pacific side of the Arctic?
Will it be able to fend off the attacks from the west, just like in 2010 and 2011?
How fast will the ice on the Atlantic side disappear?
What will the effect of that be on local SSTs and the adjacent ice edge?

Very good summary, Neven.
Regarding the ice thickness on the West side of the Arctic (Chuchki and Beaufort and Bering), it's been a very harsh winter out there, with ice extent was larger than in (satellite) recorded history.

In fact, an interesting feature called an 'ice arch' appeared in the Bering sea, when these Northern winds stacked up ice in the shallow Bering to the point where it was actually 'choked' with sea ice.

Now, to give an idea on how bad these 'ice arches' can get, in early June 1959, the "Nautilus met a mile-long ice floe that projected more than 60 feet below the surface in the Chukchi Sea."


I doubt that ice stacked up that much this time, and even if it did, the much warmer Arctic nowadays will surely melt out that ice faster than in June 1959, but I would seriously be surprised if the West Arctic will melt out as fast as it did last year or any time in the past decade...

The East (North Atlantic side)...well, as Neven points out, is the complete opposite...

Hans Verbeek

"Late freeze up usually means early melt down"
I'll have to take your word for that.
In Holland we say: results from the past don't guarantee the future.

It takes heat (energy) to melt the ice. I sincerely hope that the sun will give the normal amount of light this summer to melt the usual amount of ice.


Agreed, Hans. But the ocean is also a source of heat, and the wind can blow ice floes to places where the sun does shine.

Although I have severely underestimated the potential of the late freeze-up and the start date for the melting season, I still think we're going to see a very rapid decrease in extent/area in the coming weeks. All the trend lines of the past several years will be huddled together. Whether 2012 follows in the footsteps of 2010 and 2011 with their very sharp drops in June and July, remains to be seen.

But early melt down of ice that froze up late? Definitely. We're already witnessing it in the Bering Sea and Okhotsk. Kara and Baffin are next. Somehow I don't think the ice in the Laptev Sea is very solid either, and I'm curious to see what the Hudson Bay has in store this year.


Neven, I'm just wondering where that heat source will be, the Northern Pacific looks pretty cold at the moment.


Some of that cooling will be due to the melting ice, but the rest?

As for the other side of the Arctic, my money has always been on the effects of weather, rather than climate, on ice extent, with some underlying ocean cycles thrown in for good measure. But whatever the cause, thanks for all your hard work on this site. It is great to have a such a reliable source of information (even if I don't always agree with all of the commentary!).


Thanks, Karl!

Ned Ward

Chris Biscan writes:

And for being thicker this season so far we have this from the Beaufort region [actually, not all in the Beaufort region - Ned]:

ITP56 was deployed on a 1.5 m thick icefloe in the Transpolar Drift on April 15, 2012 at 89° 19.5 N, 1° 54.8 E [...]

ITP63 was deployed on a 1.27 m thick icefloe in the Canada Basin on April 20, 2012 at 83° 26.9 N, 115° 50.0 W [...]

ID Code: 300034012994830
Date: April 12, 2012
Type: First year ice
Initial Location: Beaufort Sea [...]
Initial ice thickness: 153 cm
Initial snow depth: 25 cm [...]
Lat: 71.511 deg
Lon: -154.690 deg

OK, that's just three points. So take this all with a large grain of salt. But I followed Neven's link to the ACNFS ice thickness maps, downloaded a map from 2012 April 18 (more or less in the middle of the observations Chris copied & pasted in his comment above), georeferenced it, and checked the pixel values at those three locations.

Here are the reported model ice thickness estimates from ACNFS:

ITP56: ~2.5 m (ACNFS) vs 1.5 m (observed)

ITP63: ~3.75 m (ACNFS) vs 1.27 m (observed)

300034012994830: ~3.1 m (ACNFS) vs. 1.5 m ice + 0.25 m snow (observed)

So, for three of three points, the modeled ice thickness seems to be overestimated, by around 1 to 1.5 meters.

Three is a small sample size, however.


ACNFS definitely isn't perfect, as was mentioned last year by someone from the Naval Research Laboratory. I'm sure they're working on it.

Chris Reynolds

Hi Karl,

The water temperatures in the Bering sea seem within normal range. Once the ice starts to recede we'll at least see a summer extent typical of the post 2007 era.
e.g. AMSRE for April 2009.

Chris Reynolds

Ned Ward,

Using this page:

I took the initial thicknesses and plotted them by month and region. No persuasive change in thickness over the period concerned. This might seem odd, but the placement of bouys is specifically done on thicker floes. So it's quite possible that this data could miss significant thinning and 'rotting' of ice.

On a related note, this might be of interest.

Barber, 2009, "The perennial pack ice in the southern Beaufort Sea was not as it appeared in the summer of 2009."
Apologies if I came across it here, I can't recall how I came across it.


Recently I calculated some yearly means, using monthly data from NSIDC.
Mean NH extent over the year 2011 was 10.66 million km2, a record low (a little bit lower then 10.68 in 2007).
Mean NH+SH extent in 2011 was 22.51 million km2, also a record (22.72 in 2007).

Perhaps this is old news? Didn't read much about it.

Daniel Bailey

Climate Progress picked this up as a repost here.


Thanks to you guys at SkS reposting this blog post here. :-)

Artful Dodger

Neven wrote:

it would seem to me that satellites can’t measure SSTs when the sea is covered by ice"

By convention when the sea surface is more than 50% ice covered, then the sea surface temperature (SST) represents the freezing point of the water. This in turn is a function of its salinity.

There is an important physical transition that occurs in sea water cooling when its salinity is above about 30 psu. Water this salty will sink as it cools, as opposed to fresher water will just freeze on the surface. When cooler water sinks, it is replaced by deeper warmer water, and the surface remains unfrozen until the entire homogeneous water column cools to the freezing point. This may not occur in a single season, especially when heat content is augmented by meridional heat transport. This of course is enhanced as the pack ice retreats.

This is one reason why the saltier waters of the North Atlantic do not freeze over Winter, even though SSTs can be as low as -4C. Mechanical turbulence is the rest of the story. As ice retreats in the Arctic basin, and storm-induced mixing of the surface layer becomes wide spread, a dramatic and perhaps permanent loss of sea ice cover may occur.

Seke Rob

Time to revive the "days per million lost / gained chart". Hope it will not be too off, moving forward / backward, but the talk indicates we're heading for new step melt records. Onset was late, so some are bound to go / have gone faster.

(Can't get access to photobucket at this time, so it will be later.)


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