Since the NSIDC produced its press release on the first of October, with the end of the ‘melt season’, there have been some comments on the blogs about the past season, but nobody seems to have noticed this.
The sea ice area anomaly exceeded -2.3 million km2 in September, during the period of minimum cover. But in the past couple of days, it seems to have gone even lower than that; the current anomaly is as great, if not greater, than it was last month.
The sea ice is returning, with some areas seeing reasonable refreezing rates, but overall, there is a lower ice area relative to the long-term date average than ever before, or so it looks. The simple explanation is that it is taking longer than usual for the refreeze to happen, which under the circumstances is not a great surprise.
It’s only a few weeks into the Arctic cold season yet, so what the Winter will bring is unknowable (seasonal variation really is a very strong signal) , but the start does not augur well. My suggestion is that we keep our eyes on the progress of the refreeze for a while yet. Historically, the Winter anomalies have been less extreme than the Summer ones, so we should expect, on average, to see that area anomaly rise, sooner or later. But that ‘sooner or later’ is also significant, as the final level of recovery will likely be affected by the timing of the refreeze.
Keeping my eyes on this one…
Old man in a cave 
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October 11, 2007 at 4:36 pm
john
Two questions: all the ice regrowth this year will obviously be single year ice, so presumably the record melt has removed a lot of multi-year ice. Significance?
And secondly, this has been so startling that there’s not been a lot on noise on Greenland seasonal melt. How’s that going, so to speak?
October 11, 2007 at 6:41 pm
fergusbrown
If you look at the animation on the NSIDC pressroom page, you can see a simplified model of the loss of multi-year ice over the past 20 years or so.
There are a great many reasons why this is potentially significant, but sticking with the areal measurement, it implies that, come the Spring, ice melt will be more rapid and more extensive than previously, for comparable conditions. Whether we get comparable conditions to this year is another matter entirely.
There’s some information on Greenland’s year so far here: http://www.nasa.gov/vision/earth/environment/greenland_recordhigh.html
but quite a few people are a bit annoyed by the presentation of the information, which is not very clear. Basically, the GIS continues to melt at ever increasing altitudes during the Summer.
One possible consequence of the changing sea ice and snow conditions in the Arctic is the rate of glacier outflow. I believe that this generally slows to a near halt if the sea is frozen beyond the glacier; this year, several of the key glaciers may not see this happen until very late in the Winter, suggesting an increase in the net contribution of these glaciers to sea level. (No, not even in inches).
October 11, 2007 at 9:01 pm
tamino
Another impact of the disappearance of thicker multi-year ice is that the thinner annual ice is more easily pushed around by winds. According to NASA research, this is one of the reasons for the astounding record lows this year; thinner ice was easily pushed out of place, into more southerly warmer waters where it was quickly melted.
Next year we’ll have even less multi-year ice, and may see even more dramatic lows. Is the polar ice cap the canary in the coal mine?
October 11, 2007 at 9:59 pm
Gareth
Well, I did point out something similar in a comment at Eli’s warren yesterday… 😉
Every year the atmosphere and ocean are pumping more heat into the Arctic than the region can lose to space over winter. This is a cumulative process, with a positive feedback – the albedo effect. In this respect the shape of the curve at CT is very interesting. I emailed them to ask if they could put the current data “on top” of last years, but no dice (or no reply..). If you look at the shape of the graph, you can clearly see the impact of warm and cold (normal?) months on the freeze. Last November was very mild.
Fergus, on the synoptics point we touched on a few days ago, you might find this page (and the presentation linked to in the text) interesting.
October 11, 2007 at 11:16 pm
fergusbrown
The thing I know little about (add it to the list) is fast ice, or landfast ice. I got the impression from slimming the ACIA that its a pretty darned important thing in some way or another. As far as I can recall, at some stage during the course of this year or another, about the only places where the sea ice permanently ‘touched’ the land was at the extreme tip of Greenland and the far north of Ellesmere Island.
As I say, I need to go and find out about this, but I am fairly sure it worries me. The other thing that worries me is the glacial outflow from Alaska Northern Canada and Siberia, which may have been quite rapid this year.
TBH, the scale of the whole thing is really rather difficult to comprehend, whatever analogy or comparison you try to use.
October 12, 2007 at 3:19 pm
J
I’m not sure what you mean by worrying about “glacial outflow from Alaska Northern Canada and Siberia”. Are you still referring to the effects of Arctic sea ice, or just general melting of glaciers in the region? Because I don’t believe there are any sea-level glaciers on the Arctic coast of Alaska, and there are relatively few Siberia (basically, just in Severnaya Zemlya I believe, and Novaya Zemlya if you count that as Siberia).
October 12, 2007 at 4:08 pm
Hank Roberts
Gee, the line actually fell off the bottom of the chart.
That’s embarassing. I wonder if they’ll expand the white space on the bottom to catch up with the falling number being charted.
Looking at papers on plankton in the Arctic Ocean I find a lot of info about life under the ice, and mentions that there’s been a layer of a few meters of low-salinity cold water on top of more salty water.
I’d guess this is now being mixed where there’s open water exposed to the wind, and we know the wind’s been different — I wonder if the layer of fresher water actually gets either mixed in and/or moved sideways by the wind, changing the rate at which the surface can refreeze.
October 12, 2007 at 4:19 pm
fergusbrown
I was thinking about the glaciers, both in terms of accelerated motion/mass loss, and contribution to runoff. There is a recent paper on BC glaciers here (yes, it’s not the high Arctic): http://www.agu.org/pubs/crossref/2007/2007GL030780.shtml
but this can be looked at in the light of work by Carter, Dyurgerov, Serreze and others. You are right about the Siberian glaciers, but then you can add Svalbard and Norway. Alaska has relatively few ‘North-facing’ glaciers, but very many ‘around the corner’ (West + South). There are, however, a fair number of glaciers in Canada, eg. Ellesmere Island and, of course, Greenland. I included the three main areas to be inclusive, rather than to imply comparable significance, however, the glacial contribution to runoff applies to all the major river basins in the region feeding the ocean.
Thanks for the correction.
October 12, 2007 at 4:25 pm
fergusbrown
Hi Hank. If they do add some more white space, that’ll be the second time this year. A couple of months ago, CT expanded its anomaly graphics from -2M km2 to -2.5, to accommodate the rate of decline. Which is kind of poignant in itself.
The layering of water types is a complex subject. I believe it is effected by the rate and timing of runoff from the major river basins as well as the wind and drift patterns. Don’t know what happens in the Autumn/Winter, though; accelerated vertical mixing?
October 16, 2007 at 11:38 pm
Steve Bloom
More white space was added today, although only to about 2.7 rather than all the way to 3.