We knew that observations by the CryoSat-2 satellite were by and large confirming the modeled data from the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) at the Polar Science Center, because of the recent publication in GRL of Laxon et al.'s CryoSat-2 estimates of Arctic sea ice thickness and volume,
but now it's official.
Here's the press release from the National Environment Research Council:
CryoSat-2 mission reveals major Arctic sea-ice loss
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.
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.
"The data reveals that thick sea ice has disappeared from a region to the north of Greenland, the Canadian Archipelago, and to the northeast of Svalbard," says Dr Katharine Giles, a NERC-funded research fellow at the Centre for Polar Observation & Modelling (CPOM) at UCL (University College London), who co-authored the report, published online in Geophysical Research Letters.
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.
Other satellites have already shown drops in the area covered by Arctic sea ice as the climate has warmed. Indeed, sea-ice extent reached a record minimum in September 2012. But CryoSat-2, launched in April 2010, differs in that it lets scientists estimate the volume of sea ice - a much more accurate indicator of the changes taking place in the Arctic.
"While two years of CryoSat-2 data aren't indicative of a long-term change, the lower ice thickness and volume in February and March 2012, compared with same period in 2011, may have contributed to the record minimum ice extent during the 2012 autumn," says Professor Christian Haas of York University, Canada Research Chair for Arctic Sea Ice Geophysics, co-author of the study and coordinator of the international CryoSat sea ice validation activities.
Well, I'll be damned, it looks like someone notified the BBC before me! Jonathan Amos writes:
The data gathered so far by Cryosat were compared with information compiled by the US space agency's (Nasa) Icesat spacecraft in the mid-2000s.
For autumn (October/November), the analysis found the Icesat years from 2003 to 2008 to have recorded an average volume of 11,900 cubic km.
But from 2010 to 2012, this average had dropped to 7,600 cu km - a decline of 4,300 cu km - as observed by Cryosat.
For winter (February/March), the 2003 to 2008 period saw an average of 16,300 cu km, dropping to 14,800 cu km between 2010 and 2012 - a difference of 1,500 cu km.
The smaller relative decline in winter volume highlights an interesting "negative feedback".
"Thin ice grows more quickly than thick ice in the winter. Ice acts as an insulator - the thinner the ice, the more heat can be lost to the atmosphere and the faster the water beneath the ice can freeze," Dr Giles told BBC News.
"But even with an increased ice growth during the winter, we can see from the Cryosat data that it's still not fully compensating for the deep summer melt."
Cryosat's altimetry observations agree well with independent measures of sea-ice thickness derived from aircraft surveys and under-ice moorings.
They also look very similar to the simulations coming out of Piomas (Pan-Arctic Ice-Ocean Modelling and Assimilation System), an influential computer model that has been used to estimate Arctic sea-ice volume and which has been the basis for several predictions about when summer sea ice might disappear completely.
"The decline predicted by Piomas is slightly less in the autumn and slightly more in winter, but broadly speaking there's good agreement," said Dr Giles.
I guess we keep an eye on PIOMAS, eh?
In memoriam: Dr. Seymour Laxon, lead author of this very important study