Tag: Arctic sea ice

Cracking up

Wilkins2009422.gif

With the “pin” to Charcot Island gone, big cracks that first formed in 2008 are are opening up in the Wilkins ice shelf, and a new break up is taking place close to Latady Island. The animation above uses ESA “webcam from space” images captured on April 18 and 21 (the latter has black corners). Latady Island is bottom left. Judging by the scale on the NASA image below, the big crack above bottom right has opened up by a couple of kilometres, and the whole assemblage of chunks of shelf are moving northwards. It’ll be interesting to see if new cracks form deeper into the shelf (bottom right) as the new bergs move away. Meanwhile, NASA’s Earth Observatory helpfully provides a new photo-like image of what was the base of the ice bridge, captured by the Terra satellite on April 12:

NASAWIlkins200904.jpg

And while we’re on the subject of ice, the Earth Observatory has just posted an excellent new feature article on sea ice, covering both ends of the planet and illustrated with some spectacular imagery. Well worth a read for anyone wanting an in-depth introduction to the state of play before the Arctic melt season really gets underway.

[Nick Lowe]

Melt away

NSIDC20090406thumb.jpg As winter turns to spring and the melt season begins, the Arctic sea ice looks to be primed for another bad summer. Multi-year ice is down to only 10% of the total extent — down from 40% during 1979-2000, and new work on ice thickness suggests that the ice cover is thinner than at any point in the recent past. At a NASA/NSIDC press conference discussing the new data, UC Boulder scientist Walt Meier commented:

“We’re not set up well for summertime,” ice data center scientist Walt Meier said Monday. “We’re in a very precarious situation.” [Associated Press]

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Come a little bit closer

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Estimates of when the Arctic will be substantially ice free in summer used to be out towards the end of this century. In 2007, the IPCC’s fourth report suggested that there would still be a fair amount of summer ice in the 2080-90s, but the record minima of recent summers have been forcing a rapid review of that expectation. We’ve had “rough” estimates of perhaps the 2030s, and even a suggestion it could happen as early as 2013 (follow the sea ice tag for earlier posts). A new paper by Wang and Overland in this week’s Geophysical Research Letters takes a more quantitative approach, by using six models and priming them with the sea ice state after the dramatic melt seasons of 2007 and 2008 (NOAA press release):

The area covered by summer sea ice is expected to decline from its current 4.6 million square kilometers (about 2.8 million square miles) to about 1 million square kilometers (about 620,000 square miles) – a loss approximately four-fifths the size of the continental U.S. Much of the sea ice would remain in the area north of Canada and Greenland and decrease between Alaska and Russia in the Pacific Arctic.

You can see the ice distribution in the small image at the top of the post (click on it for the larger original). The paper’s abstract tells us when this might happen:

Using the observed 2007/2008 September sea ice extents as a starting point, we predict an expected value for a nearly sea ice free Arctic in September by the year 2037. The first quartile of the distribution for the timing of September sea ice loss will be reached by 2028.

I interpret that to mean that the central expectation is 30 years, but some models suggest it could be a decade earlier. I wonder what effect that might have on the permafrost and methane hydrates… AP coverage here. Meanwhile, the NSIDC has declared this winter’s maximum extent was reached on February 28th, at 15.14 million km2 — the fifth lowest winter maximum in the record. They note:

The six lowest maximum extents since 1979 have all occurred in the last six years (2004 to 2009).

The betting season is now open. I’m on double or quits with Stoat (aka wmconnolley when he shows up here), but as he’s offering 2-1 to newcomers, I might be back to evens. I think I’m also betting with malcolm (Vibenna) again… I won’t offer any sort of form guide until later in the season, but (as ever) I’m hoping to lose, but at least half expecting not to.

[Jay & The Americans]

We can run, but we can’t hide…

earthhour.jpg This article appeared in the Perspectives section of The Press yesterday, as part of the paper’s build up up to Earth Hour this weekend. I haven’t seen the letters page today, but I expect the usual suspects will be out in force… 😉

The news isn’t good. Since the Intergovernmental Panel on Climate Change (IPCC) advised two years ago that the evidence for global warming was unequivocal, the pace of change has speeded up. Summer sea ice in the Arctic Ocean has seen a dramatic decline, and in a worrying foretaste of what may be to come, methane — a much more powerful greenhouse gas than carbon dioxide — has been found bubbling out of the ocean floor off Siberia. Down south, analysis of a core drilled into the seabed under the Ross Ice Shelf by a team including scientists from New Zealand (using Kiwi drilling expertise), demonstrates that the West Antarctic Ice Sheet is unstable and likely to collapse if warming continues as we expect over the coming century. Experts are revising their projections of sea level rise upwards with each piece of bad news. A metre or more by the 2090s is now a real possibility.

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Nutted by reality

homer.jpgGerrit van der Lingen, a local crank, NZ CSC member and self-styled “climate change consultant” who comprehensively lost a magazine “debate” with a local scientist last year, was mightily exercised by a recent article in my local paper, The Press (one of New Zealand’s big four dailies), covering Lovelock’s latest ruminations. So incensed, in fact, that he was moved to regurgitate a few crank tropes for an op-ed in the paper last Wednesday. It’s not available on the web, sadly, so I’ll just confine myself to pointing out where he gets his facts wrong.

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