Friday, March 8, 2019

Bering Sea Meltout

The big story in Alaska climate at the moment is the near-complete loss of sea ice in the Bering Sea in recent weeks.  Unrelenting warm southerly flow has reduced Bering Sea ice extent to a record low level for the date, dropping below even last winter's remarkable ice shortfall.  The climatological peak in Bering ice cover occurs at the end of March, but the latest daily ice extent of only 150,000 km2 is more typical of about June 1st, according to the 1981-2010 normal.

With only about 20% of normal ice cover for the date, the current anomaly is the greatest percentage shortfall (relative to normal) between about mid-December and mid-April (mid-May prior to last winter), so it's safe to say that such an extreme absence of winter ice has not been observed previously in the modern satellite record.

It's also of interest to note that the last 40 days have seen a decrease of 417,000 km2 in sea ice extent, and a 40-day loss of this magnitude has not previously been observed this early in the season.  The earliest was between mid-February and late March of 2002, but that was starting from over 900,000 km2.

Here's today's ice analysis from the National Weather Service (click to enlarge).

A few days ago the NWS map was also showing considerable ice loss north of the Seward Peninsula and in Kotzebue Sound, and today's satellite imagery suggests (to me at least) that the remaining ice in this area is broken and insubstantial.  The image below (3pm AKST today) is rather obscured by clouds, but the Seward Peninsula and a dark-looking Kotzbue Sound are visible just to the right of center.

A webcam image from Kivalina this afternoon also suggests there is a lot of open water in the southeastern Chukchi Sea; note the obvious dark band along the horizon.

The Iditarod mushers will be reaching the Bering Sea coast tomorrow, but unless the teams need to cool off, it seems they'll be confined to land as they travel up to Nome.  Here's the ocean view from Shaktoolik this afternoon.  Air temperature: 37°F.

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