Friday, February 15, 2013

Arctic death spiral: sea ice volume has collapsed

Back in September, Climate Progress reported that the European Space Agency’s CryoSat-2 probe appeared to support the key conclusion of the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) at the University of Washington’s Polar Science Center: Arctic sea ice volume has been collapsing much faster than sea ice area (or extent) because the ice has been getting thinner and thinner.The sharp drop in Arctic sea ice area has been matched by a harder-to-see, but equally sharp, drop in sea ice thickness. The combined result has been a collapse in total sea ice volume — to one fifthof its level in 1980.

Now the Natural Environment Research Council (NERC), the UK’s primary agency for funding and managing environmental sciences research, has made it official. In a Wednesday press release, they report:
Arctic sea ice volume has declined by 36 per cent in the autumn and 9 per cent in the winter between 2003 and 2012, a UK-led team of scientists has discovered….
The findings confirm the continuing decline in Arctic sea-ice volume simulated by the Pan-Arctic Ice-Ocean Modelling & Assimilation System (PIOMAS), which estimates the volume of Arctic sea ice and had been checked using earlier submarine, mooring, and satellite observations until 2008.
This should be the story of the day, week, month, year, and decade. As NERC notes, sea ice volume is “a much more accurate indicator of the changes taking place in the Arctic.”
Many experts now say that if recent volume trends continue we will see a “near ice-free Arctic in summer” within a decade. And that may well usher in a permanent change toward extreme, prolonged weather events “Such As Drought, Flooding, Cold Spells And Heat Waves.”
It will also accelerate global warming in the region, which in turn will likely accelerate both the disintegration of the Greenland ice sheet and the release of the vast amounts of carbon currently locked in the permafrost.
The findings were published online in Geophysical Research Letters (subs. req’d). In a U. of Washington news release, polar scientist and coauthor Axel Schweiger said:
Other people had argued that 75 to 80 percent ice volume loss was too aggressive. What this new paper shows is that our ice loss estimates may have been too conservative, and that the recent decline is possibly more rapid.

Researchers used new data from the European Space Agency’s CryoSat-2 satellite spanning 2010 to 2012, and data from NASA’s ICESat satellite from 2003 to 2008 to estimate the volume of sea ice in the Arctic.
They found that from 2003 to 2008, autumn volumes of ice averaged 11,900 km3. But from 2010 to 2012, the average volume had dropped to 7,600 km3 - a decline of 4,300 km3. The average ice volume in the winter from 2003 to 2008 was 16,300 km3, dropping to 14,800 km3 between 2010 and 2012 – a difference of 1,500 km3.

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