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L. Hamilton

For the numerically inclined:

Cryosphere Today global area
Year | max(areaG)
1979 | 22.1967
1980 | 22.9964
1981 | 22.619
1982 | 22.5138
1983 | 22.6862
1984 | 22.2494
1985 | 23.3375
1986 | 21.9697
1987 | 22.328
1988 | 23.4132
1989 | 22.2603
1990 | 22.1872
1991 | 21.9272
1992 | 22.759
1993 | 22.8465
1994 | 23.1768
1995 | 21.5579
1996 | 22.5981
1997 | 22.1105
1998 | 22.3401
1999 | 22.2944
2000 | 22.3633
2001 | 21.1583
2002 | 21.6619
2003 | 21.6866
2004 | 22.1252
2005 | 22.0508
2006 | 21.7763
2007 | 21.2337
2008 | 22.177
2009 | 21.0034
2010 | 21.1515
2011 | 20.9022

L. Hamilton

33-year trends in global sea ice area, in round numbers (all statistically significant):
max -45,000 km^2/year
mean -41,000 km^2/year
min -35,000 km^2/year


First time below 21 million.

L. Hamilton

Remember when "global sea ice" would be raised as a talking point against global warming, with the claim that Arctic ice might be declining but global ice was not? I'm not sure what that was based on, possibly just eyeballing a monthly graph. But the yearly max, min and mean tell a pretty clear tale:


In this graph, the mean for 2011 runs just through 11/11/11. If we have indeed passed the maximum, the final mean for 2011 should be slightly lower.

Account Deleted

So, is it official that we reached maximum sea ice? Is there no possibility that ice starts to pick up again in a few days?


It's not official yet, Daneel. But personally I don't think it's going to go higher than this.


This blog is beginning to sound like a broken record ;-)



I can't help it, Hans!



BTW. Have you seen the recent NH snow cover compared to last year?


Yes, that's very interesting. Andrew Xnn posted two graphs in the October open thread. It looks like ocean effect snow kicked into action in 2007.


Ocean effect snow, sounds good.
But how to explain the increased snowfall in Oct, Nov and Dec.
Are the oceans warmer in general or just relatively warmer than the upper atmosphere over the continents?
Why did snowfall start to increase in 2007 and why not in 1998?
Or is the average over the period 1966 - 2010 abnormally low?

L. Hamilton

A few more indications that the max record might be broken:

1. Global area declined almost a century on day 315.

2. The latest previous max (in 2010) was on day 314.


Wayne Kernochan

Based on the latest Arctic figures, I anticipate the next global area figure will come in about 2 km**2 lower, putting it 40 km**2 below the 2009 maximum (previous record). If all the disrupted Bering sea ice were to refreeze today, that would still only add about 20 km**2 to the global sea ice area -- and from then on the trend is overwhelmingly down. Imho, you can put this record in the bank.


But how to explain the increased snowfall in Oct, Nov and Dec.

I'm not an expert, but we're halfway November, and there's still a lot of open water -> Barentsz, Hudson Bay. These waters still have to release their heat. So that would be a source of water vapour that could come down as snow on the continents.

Are the oceans warmer in general or just relatively warmer than the upper atmosphere over the continents?

Well, the Arctic Ocean seems to be warmer in the past couple of years, due to warmer ocean currents going into it, and also due to the albedo effect.

Why did snowfall start to increase in 2007 and why not in 1998?
Or is the average over the period 1966 - 2010 abnormally low?

My guess would be that there was so much open (and very warm) water in 2007 that we could call it a shift. Especially now that the 4 years after it have followed suit.

Maybe we can expect lots of early snow on the NH continents practically every year from now on and for a while to come.

Unfortunately it also melts out very rapidly when spring arrives.

Wayne Kernochan

@L Hamilton: I would suspect somewhere around 100% of the change in global is from the change in Arctic area. It would be interesting to chart the difference from, say 1979 in Arctic vs. global (in your copious free time :)). At any rate, that's what I seem to see in the latest Antartic figures.

One of the problems I have with the Antarctic figures is that the boundary between sea and land ice is not as clearcut. For example, it seems as if the Ross Sea sea ice may not be included, at least the way NSIDC presents it visually. As I understand it, over the last 30 years the Ross Sea ice shelf has been melting from the bottom up in the middle of the shelf, between the summer outer boundary and the land. Right now, that melting is apparently simply causing the inland glaciers to flow faster (less drag), but eventually it should surface and either (a) melt outwards to the outer shelf boundary or (b)establish a new outer shelf boundary closer to the land. Either way, at some point there should be some major additions to Antarctic (seasonal?) "sea ice" that may skew the figures.

The point of this is that I am wondering if this has not been going on all along: if the outer boundaries of Antarctic sea ice are decreasing in their amount of sea ice, but new ice from the shelves is being added at the same time, thus giving a misleading impression of there being just as much sea ice as before. This would explain why there seems to be little if any effect of Antarctic sea ice on the global total. Any thoughts?

Chris Reynolds


The Antarctic sea-ice has been growing, despite coastal warming of Antarctica. Zhang explains why this has been happening in "Increasing Antarctic Sea Ice under Warming Atmospheric and Oceanic Conditions."

I think there may be changes in the ice sheets that impact the areas from which ice is considered to be sea-ice. But I suspect that they're likely to be small in comparison to the overall area of sea ice.

Wayne Kernochan

@Chris R: I just took a brief scan, and was really put off by the fact that he was using "extent" as a proxy for "area" (volume seems irrelevant when most of the sea ice melts and then reforms each year). As the winds' energy increases, one would expect a greater extent for the same area, as the rotational motion of currents and winds pushes the ice outward more strongly, yielding lower concentration. Over the period 1979-2011, what I see is somewhat of a decrease in area until somewhere around 1993, then an increase until somewhere around 2000-2007, and then a leveling off at the same amount as at the beginning (I may be reading the area data wrong, of course; I was focused mostly on minimum data).

Now, according to his theory, what I should have seen if area is equivalent to extent is a steady if slow increase in area over that entire time period. Moreover, last fall the deniers were trumpeting the fact that global extent seemed to be approaching a record high anomaly, due to the fact that Antarctic extent was way high; but area was only slightly high and well within a couple of standard deviations, which meant, apparently, that concentration was at or near a record low. Which, to me, supports the argument I made above that as time goes on, concentration should, if anything, decrease, and therefore the right measure is area.

Of far greater significance is that recently Antarctic sea ice minimum area has been close to the record minimum. Moreover, in the last 6 or so years, most Antarctic area daily records are showing 75-85% of the days with negative anomalies, with the record being about 85% (there won't be one this year, due to some recent over-anomaly days, but until October, 2011 was leading the pack). To bring the topic back to this thread, that's why I'm anticipating another brush with the global minimum area record -- that and my bet that Arctic area will also be at or near a record low for that date (somewhere in January).

Maybe we can expect lots of early snow on the NH continents practically every year from now on and for a while to come.

Unfortunately it also melts out very rapidly when spring arrives.

I agree, the effect on the albedo will be small because of the rapid melting.
I'm more interested in the amout of heat required to make snow and melt the snow again.

More snow means more evaporation and that will cool the oceans.
And it takes more (latent) heat to melt snow on the ground, than to warm liquid water of zero degrees.
How much snow would have to melt to offset the manmade global warming?

It is a very complex insolvable puzzle.

Pete Dunkelberg

This paper although not a surprise, may add some clarity to the overall sea ice picture:

Eisenman et al. 2010 Consistent changes in the sea ice seasonal cycle in response to global warming

The Northern Hemisphere sea ice cover has diminished rapidly in recent years and is projected to continue to diminish in the future. The year-to-year retreat of Northern Hemisphere sea ice extent is faster in summer than winter, which has been identifed as one of the most striking features of satellite observations as well as of state-of-the-art climate model projections. This is typically understood to imply that the sea ice cover is most sensitive to climate forcing in summertime, and previous studies have explained this by calling on factors such as the surface albedo feedback. However, in the Southern Hemisphere it is the wintertime sea ice extent that retreats fastest in climate model projections. Here, we show that the inter-hemispheric differences in the model projections can be attributed to differences in coastline geometry, which constrain where sea ice can occur. After accounting for coastline geometry, we fnd that the sea ice changes simulated in both hemispheres in most climate models are consistent with sea ice retreat being fastest in winter in the absence of landmasses. These results demonstrate that despite the widely differing rates of ice retreat among climate model projections, the seasonal structure of the sea ice retreat is robust among the models and uniform in both hemispheres.

Chris Reynolds

Thanks Pete,

That Eisenman paper is available from Cecilia Bitz's homepage:
But I've not read it and want to before commenting further.


The paper I referenced is by Jinlun Zhang who's one of the main movers behind PIOMAS. His work is pretty sound - if the model shows what he says it does I'm biassed to go with him. However I last read that paper some years ago and want to read it again. There's also some research I vaguely recall by Corrinne Le Quere - something about an increase in the Antarctic Circum-Polar current that was drawing water away from Antarctica and allowing warmer bottom water to well up, so reducing CO2 uptake in the Southern Ocean - remember Corriolis works the other way in the southern hemisphere.

I'll reply in a day or two.

Chris Reynolds


From Zhang:
"Contrary to this warming trend, satellite passive microwave images display a significant increase in Antarctic sea ice concentration and extent since 1979 when quality space-based observations are available."

Wayne Kernochan

@Chris R: Thanks for finding that. This clearly implies that area is up -- by more than extent. Unfortunately, since early 2006 when he wrote it, the area data shows, if anything, a downward area trend. 1979-1981 all show a slightly negative anomaly (counting only the number of +s and -s), while 2006 and 2007 show a greater negative anomaly, 2008-2010 show a slight to pronounced positive anomaly, and 2011 so far shows a near-record negative anomaly. Combining them together, there is no way that 1979 to 2011 show a definite, pronounced increase in average area. Unfortunately, I don't see any extent figures, but I do know, as I've noted, that last fall extent was near a record high anomaly, while area was nowhere near that. That does not indicate to me a pronounced increase in concentration. I suspect that either the Antarctic sea ice trend evolved beyond what was going on 5 years ago -- a "tipping point", if you will, of warming -- or it was one of those statistical situations where, unlikely as it seems at the time, there is no upward trend.


I think that increased sea ice is an inevitable consequence of warming. as the Antarctic is primarily land based ice. massive melting on land will dump cold fresh water and ice into the sea negating any reduction in sea based ice created by winter freezing.

Artful Dodger

PoF, you're right. In fact, James Hansen agrees with you.

Wayne Kernochan

Actually, I think that PoF and AD are somewhat confirming my (tentative) theory, not Zhang's apparent one. My suggestion was that increased melt at the edges was being counterbalanced by receding of the boundaries of ice shelves, of which the one in the Ross Sea was the most massive. Anecdotal confirmation comes from a post in Boing Boing referenced by this blog, which stated that for the last five years at least the "melt line" in summer near McMurdo Station had been getting (overall) further and further south and closer and closer to McMurdo.

The question then becomes, how do we isolate the effect of edge melting, to get a better picture of Arctic-style sea ice decrease independent of land effects?

Mike Constable

Have noticed some persistent streaks on the Ross ice shelf images for 16 &17 November. I believe splitting of the ice shelf can produce a line of cloud which can show on satellite images.One streak in the centre of the ice shelf front (running back towards McMurdo Base) ties in with a known calving line. But now there are two more streaks south west of that one - do they show weakness in the body of the Ross ice shelf? http://amrc.ssec.wisc.edu/ice_images/icebergs/ross/new_images/LATEST_ROSS_SHELF_tempC.GIF
There is another streak running parallel to the shelf front from the island in the east that has been there for a long time (7+ years)

Chris Reynolds


The long term trend has small variations in the series it's derived from.
The above link to anomaly shows this. There is nothing going on at present as far as I can see that suggests new processes are at work. The current apparent decrease in anomaly is similar to 1988 - 1993 and 2002 - 2006.

Furthermore Zhang uses a run where precipitation (snowfall in this case) does not increase, yet the model still produces an increasing trend in Antarctic sea-ice.

I still back Zhang on this.

However as I have to read (and probably blog on) the recent IPCC report into climatic extremes and impacts I'm going to bow out of this discussion.

Rob Dekker

DMI shows 80 deg+ temps are WAY up...

Wonder what's up with that ?


Rob, I don't think it's an artifact. NOAA shows the same thing.

Rob Dekker

Thanks Neven, The warmth is spacially pictured right here :


Barely below freezing all around the North Pole, and it shows that most of the Atlantic side of the Arctic sea ice growth came to a grinding halt.

Is this due to that big low that seems to intensify over the North Atlantic ?

It's getting close to December, and you can still sail around and ice-free Svalbard... Pretty amazing..

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