Over the decades, the summer melt season for Arctic sea ice has become progressively longer. However, since around 2010, this trend has surprisingly slowed. A study led by NASA researchers shows that, whilst the melting season is now significantly longer than in 1979, it has not recently exhibited any further clear trend.
Since continuous satellite observations began in 1979, the Arctic sea ice melting season has lengthened by a total of around 40 days, or 51 per cent. This trend was particularly pronounced between 2000 and 2009, when the season became about 25 days longer during this period.
Since 2010, however, a different picture has emerged. The duration of the melting season fluctuates greatly from year to year, without showing a clear trend towards further prolongation. For the period 2010 to 2023, the researchers even calculated a slight shortening, although this is not statistically significant.
Cloud cover could play an important role. During the 2000s, it decreased over parts of the Arctic, allowing more solar radiation to reach the ice surface. Since 2010, however, summer cloud cover has increased again, thereby reducing the amount of incoming solar energy.
Nevertheless, there is no sign of a recovery in Arctic sea ice. Thick, multi-year ice has declined significantly, whilst large parts of the Arctic Ocean are now covered by thinner, first-year ice. This type of ice is much more sensitive to weather, wind and ocean conditions.
The study, led by Linette Boisvert at the NASA Goddard Space Flight Centre, is based on satellite data from 1979 to 2023. It was published in Communications Earth & Environment. NASA Earth Observatory revisited the findings on 21 September 2026 with new comparative maps.
Heiner Kubny, PolarJournal