Increased Arctic sea ice volume after anomalously low melting in 2013

Changes in Arctic sea ice volume impact on regional heat and freshwater budgets, on patterns of atmospheric circulation at lower latitudes and, potentially, on global climate. Despite a well-documented ~40% decline in summer Arctic sea ice extent since the late 1970’s, it has been difficult to quantify trends in sea ice volume because detailed thickness observations have been lacking. Here, we assess changes in northern hemisphere sea ice thickness and volume using five years of CryoSat-2 measurements. Between autumn 2010 and 2012, there was a 14% reduction in Arctic sea ice volume, in keeping with the long-term decline in extent. However, we observe 33% and 25% more ice in autumn 2013 and 2014, respectively, relative to the 2010-2012 seasonal mean, offsetting earlier losses. The increase was driven by the retention of thick sea ice northwest of Greenland during 2013 which, in turn, was associated with a 5% drop in the number of days on which melting occurred – conditions more typical of the late 1990’s. In contrast, springtime Arctic sea ice volume has remained stable. The sharp increase in sea ice volume after just one cool summer indicates that Arctic sea ice may be more resilient than has been previously considered.