You are currently browsing the monthly archive for September 2008.

On a new weather and climate site, Totally weather and climate, someone wrote the comment below to me:
I am watching the rise in the arctic ice very carefully as I think it really does resememble watching the signals from a life support machine. If we see significantly higher ice levels this time next year a lot more people will be asking a lot more questions. Two years in a row and possible will have become probable. It woul dbe interesting to see all of the explanations.
I live in hope.


To which I replied:

As a student of Arctic sea ice conditions, I’d advise caution over this approach. The interannual variability is huge and the signal-noise ratio small. There is only so much we can garner from any one or two seasons of watching.

As I said elsewhere, climate change needs thinking of on longer timescales to be meaningful.

Take 2008’s melt season, now apparently over; it was slightly less than record-breaking, but not by much. If there was a surprise in ice conditions this year, it was the rate of recovery over the Winter, followed by the relatively slow start to the melt season, which was probably unexpected.

Are we likely to see significantly higher ice levels (I presume here you mean the Summer minimum) next year? Given the state of the multi-year ice, I’d say no. But I’d also look at the ENSO predictions for the next six-twelve months, and try to factor this in, too. Then I’d want to look at the AO and factors such as the Bering and Fram inflow/outflow numbers, and the coming seasons’ NH snow cover (Albedo!), the general sea circulation, and areas of potential forcing such as the north Pacific, Labrador and the GIS ridge.

Taking these into account, then looking at the long term trend, a conservative estimate would be that 2009’s melt season is likely to be comparable to 2008’s, with a 25% chance of it becoming like 2007’s, or worse (though 07 and 08 were very similar, in the end).

If people see two consecutive years of summer minima close to the long term average, they might be inclined to speculate whether we really understand enough about the Arctic to use it as a benchmark for GW. Technically, they’d be wrong to do so, though it is easy to see why the temptation is there. Realistically, there is no reason, at the moment, to think that next year will be any better than any one of the last ten, ie, well below the long-term average. My predicion is that the minimum will be exceeded in the first Summer season following the next el-nino, if not before.

I’d be interested to know who agrees/disagrees with my ‘predictions’, and why; am I missing something?

The Old Man stayed out of this Spring’s sea-ice betting spree, but has been keeping an eye open nonetheless.

The average day for minimum sea-ice level in recent years has been September 8th. Last year it was around the 16th. This year, it looks like it may be a little later (late thaw, rapid August decline, no sign of strong cooling yet).

Cryosphere Today gives as its most recent number a sea ice extent of 3.08M km2. This is very, very close to last year’s absolute low level.

There is a lot of ice floating in the Greenland Sea, which looks like its being flushed out of the Fram Strait (see recent research from RV Polarstern from the AWI and others); this is not great news. But this may not have an effect on the final minimum level, as it is unlikely to be lost to the Arctic Ocean in time for the days of minimum.

This year there is more ice in the central Arctic zone, but less along the Russian coast. I haven’t looked at the atmospheric conditions in detail, but with the general flow still moving counter-clockwise and broadly outwards, it is reasonable to expect some losses still in these areas.

Interested viewers should look, in addition to the pages recommended on Uncle Eli’s site, at the Internation Arctic Buoy Program Page, The excellent AARI/AANI English language pages of the Russian Arctic research program (which show drift analyses and predictions, along with other useful data), the State of the Canadian Cryosphere’s 30 day forecast maps, and, in particular, the Polarview/DAMOCLES/IOMASA combined web pages, which also contains excellent links to other sources.

Along with Eli, I also strongly recommend Bob Grumbine’s outstanding NCEP/MMAB sea ice analysis pages.

And for those, like Antony Watts, who think there is something amiss with the difference between the outputs of different research programmes, I suggest you ask Bill Chapman, or Bob, or Julienne Stroeve/Walt Meier, to give you the twopenny tour of the differences, whcih is openly available to anyone who asks and is relatively straightforward: they use different criteria for determining what is to count as ‘ice-covered’, and slightly different methodologies and averaging processes to determine the ice extent. The matter of which you choose to take as definitive is up to the individual, but in truth they all have good reasons to use the metrics and the processes of their choice. It doesn’t make any difference, since the results in each and every case are the same; the Arctic Summer Sea Ice level is in long-term, rapid decline; a record on one system is very likely to be a record on the other.

My conclusion? There is still a 30% chance that sea-ice will continue to decline until beyond the 20th September and a new record low will be recorded this year. We should know by the end of the month. It will also be interesting to compare this year’s recovery rate with last year’s; remember, the record anomaly came in mid-October, a month after the actual minimum.


POSTSCRIPT: I see after the event that tamino has beaten me to it; interesting that our conclusions seem to concur. Sorry, tamino.


Blog Stats

  • 67,186 hits
September 2008