When the observed Arctic ice cover hit a record low last summer, I reviewed the last 20 years or so of ice coverage data, which showed a clear long(ish)-term decrease in both winter and summer ice cover, and concluded:
At this stage, then, it is difficult to know if this year’s record low represents an acceleration of the long-term shrinkage of Arctic sea-ice, or is merely part of the variability in a fairly dynamic system (as witnessed by the large changes in coverage over the annual cycle). Only time will tell: the figures for this winter could be very interesting.
Well, here is the coverage map for last month, courtesy of the National Snow and Ice Data Center:
At first glance then, all that extra open ocean observed last September has made very little difference to the winter coverage; Arctic sea ice actually has a slightly greater extent than it did in March 2007 (15.2 million square km, as opposed to 14.7 million last year). But this year, a much greater proportion of the ice sheet consists of newly formed ice, which is much thinner, and more vulnerable to summer melting, than thicker ‘perennial’ ice that has survived and grown over a few seasonal cycles. If we could measure ice volume rather than ice area, I suspect the story would be different – and more worrying. Others seem to agree.
Nice plan for content warnings on Mastodon and the Fediverse. Now you need a Mastodon/Fediverse button on this blog.