Climate Watch

Sea ice in the Bering Sea has melted away quite rapidly in the past few weeks. While the ice extended unusually far south at the end of March, briefly reaching St. George in the Pribilof Islands, sea ice in most of the northern and eastern Bering was thin and broken up, at least in part because of the repeatedly strong east winds in February and March.

So, it’s not very surprising that even with a modestly mild April, the ice has rapidly melted, though the speed of the melt is still shocking to see unfold. For example, in the two weeks between April 10 and April 23, about 120,000 square miles of the eastern Bering Sea, more than three times the area of the Seward Peninsula, transitioned from at least partially ice covered to open water. The only spring in the modern era with daily sea ice estimates (since late 1978) that had a similarly extensive sea ice decline in mid-April was back in 2004.

A significant decline in sea ice extent by late April is not new in recent years but has become much more common. One way we can consistently look at this is to examine how much ice has been lost to this point in the spring from the maximum extent. The maximum extent of Bering Sea ice is typically reached in March but has been as early as January 11 (2000) and as late as April 13 (2005). Historically, in some years, ice extent was still not much lower than the maximum, while in a few years it had retreated quite a bit. However, as you can see in the graphic, in each year since 2016, ice extent has declined by more than 20 percent from the maximum level by April 23. While individually there are similar years in the past, the lack of any years since 2016 with the ice extent still close to the maximum level for the season by the fourth week of April, is first in the 44-year satellite record.