Spatially mapped reductions in the length of the Arctic sea ice season

Satellite data are used to determine the number of days having sea ice coverage in each year 1979–2013 and to map the trends in these ice‐season lengths. Over the majority of the Arctic seasonal sea ice zone, the ice season shortened at an average rate of at least 5 days/decade between 1979 and 2013, and in a small area in the northeastern Barents Sea the rate of shortening reached over 65 days/decade. The only substantial non‐coastal area with lengthening sea ice seasons is the Bering Sea, where the ice season lengthened by 5–15 days/decade. Over the Arctic as a whole, the area with ice seasons shortened by at least 5 days/decade is 12.4 × 10 6 km 2 , while the area with ice seasons lengthened by at least 5 days/decade is only 1.1 × 10 6 km 2 . The contrast is even greater, percentage‐wise, for higher rates.