The image below shows how much the older, thicker sea ice has declined over the years. This decline doesn't become apparent when focusing on sea ice extent; volume measurements are needed to reveal this decline.
|Old versus new ice in Arctic: The maps show the median age of sea ice in March 1985 (left) and March 2011 (right).|
Overall, the proportion of old ice has decreased. By March 2011, ice over 4 years old accounts for less than
10% of the Arctic ice cover. Credit: National Snow and Ice Data Center, University of Colorado, Boulder.
The European Space Agency's CryoSat promises to deliver an even clearer picture. One of the scientists analyzing the CryoSat data, Dr Seymour Laxon, said in April 2012 that CryoSat's volume estimate is very similar to that of PIOMAS, the model developed at the Polar Science Center at the University of Washington.
In a recent interview, Dr Laxon said that if the current trend continues, the Arctic could be ice-free at the height of summer by the end of the decade.
John Nissen, Chair of the Arctic Methane Emergency Group (AMEG), comments: "Dr Laxon failed to mention the data on sea ice thickness that has been collected over many years by sea ice expert Professor Peter Wadhams of the University of Cambridge, who now considers that the Arctic Ocean will be seasonally free of sea ice most probably by September 2016. PIOMAS sea ice volume data suggest that a collapse in sea ice area could occur even sooner, as discussed on the AMEG blog posting."
The Godiva2 data comes from the GHRSST data, if it is coming from CRYOSAT, can you give me a source? I have been posting Godiva2 data for a few weeks on my website.
You are correct, Ben, I've amended the post's text to clear up confusion about that. Your site gives an excellent overview of recent changes in sea ice concentration and thickness. Let me know if you hear more on how CrySat compares with Godiva2 and PIOMAS, or any further relevant news.Delete
'John Nissen, Chair of the Arctic Methane Emergency Group (AMEG), comments: "Dr Laxon failed to mention the data on sea ice thickness that has been collected over many years by sea ice expert Professor Peter Wadhams of the University of Cambridge'ReplyDelete
The original Observer Article on this story (http://www.guardian.co.uk/environment/2012/aug/11/arctic-sea-ice-vanishing) makes explicit reference to Wadhams work with submarines and their relevance to volume changes over a longer period...
Thanks for commenting, Seymour. The article in the Guardian says that CryoSat data indicate that sea ice volume in 2004 was ~13,000 cubic km, while "in 2012, there is 7,000 cubic km". The article does also mention Peter Wadhams, adding that, compared to 30 years ago, summer sea ice has lost ~70% of volume. PIOMAS staff mention a 75% reduction in September volume from 1979 to 2011.Delete
PIOMAS data show a 2011 minimum of 4,000 cubic km. Some projections for 2012, based on PIOMAS data, point at a 3,000 cubic km minimum. You say volume was 7,000 cubic km in 2012, Seymour. What month in 2012 does your figure apply to? What do you think will the minimum be for 2012?