I'll probably update this post tomorrow (updated now, see below), but Timothy Chase writes in to say that the Guardian has an article today with news related to CryoSat-2, the satellite that has been launched to measure the thickness of Arctic sea ice (among others). So I'm putting this out now, even though it hides the latest ASI update from view, which is also well worth a read if I say so myself.
Rate of arctic summer sea ice loss is 50% higher than predicted
New satellite images show polar ice coverage dwindling in extent and thickness
Sea ice in the Arctic is disappearing at a far greater rate than previously expected, according to data from the first purpose-built satellite launched to study the thickness of the Earth's polar caps.
This rate of loss is 50% higher than most scenarios outlined by polar scientists and suggests that global warming, triggered by rising greenhouse gas emissions, is beginning to have a major impact on the region. In a few years the Arctic ocean could be free of ice in summer, triggering a rush to exploit its fish stocks, oil, minerals and sea routes.
Using instruments on earlier satellites, scientists could see that the area covered by summer sea ice in the Arctic has been dwindling rapidly. But the new measurements indicate that this ice has been thinning dramatically at the same time. For example, in regions north of Canada and Greenland, where ice thickness regularly stayed at around five to six metres in summer a decade ago, levels have dropped to one to three metres.
"Preliminary analysis of our data indicates that the rate of loss of sea ice volume in summer in the Arctic may be far larger than we had previously suspected," said Dr Seymour Laxon, of the Centre for Polar Observation and Modelling at University College London (UCL), where CryoSat-2 data is being analysed. "Very soon we may experience the iconic moment when, one day in the summer, we look at satellite images and see no sea ice coverage in the Arctic, just open water."
Dr. Seymour Laxon is obviously very busy right now, but nevertheless made time to send me some clarifications:
1) The numbers are PROVISIONAL but are our best estimates right now. We are working hard to finalise (i.e. check the details of) the numbers at which point a paper will be submitted which will hopefully be published in due course. At that point everyone will have access to the whole story/figures etc.
2) The trends are from the period 2004 to 2012 and are obtained by combining CryoSat ice volume with ice volume from NASA's ICESat mission for years 2003-2008 (see Kwok et al, JGR, 2009).
3) The trends are for the two campaign periods which ICESat operated in each year that overlap with the times of year when CryoSat-2's provides data. That is a month during October/November (ON) and February/March (FM).
4) The numbers refer only to the central Arctic (the ICESat domain) and cannot always be compared with the PIOMAS "whole arctic domain" available on the PIOMAS website (i.e. there are times of year when some ice lies outside the central Arctic).
5) Both ICESat and CryoSat-2 measurements have been validated (checked) against data gathered by aircraft and undersea moorings.
6) IF the trends we appear to be seeing continue then the Arctic may become (largely) ice free within a decade. HOWEVER to make a "prediction" of the date at which the Arctic might become ice free it will be necessary to get our data into models which are capable of making such a prediction. We are working on that also with colleagues.
7) From point 3) you may assume that our last data points are for ON11 and FM12. For the current condition of the sea ice there are many websites which show the current extent of the ice (CS-2 cannot measure thickness at this time of year with our current processing).
That's all I can say right now, but I hope that helps and I would encourage all now to wait for the paper where all of the data, methods and uncertainties will be clearly laid out (though for those who can't wait see [Giles et al., GRL, 2008] and [Kwok, et al., 2009] where measurements derived in a similar way are presented).
Thank you, Dr. Laxon, and good luck with the paper!