Warmth on the Kuskokwim

Western Alaska's exceptionally warm weather is in the news again today, as open water on the Kuskokwim River has forced a change of plans for the Kuskokwim 300 sled dog race that begins this Friday:

https://www.adn.com/outdoors-adventure/2018/01/16/unprecedented-open-water-causes-route-change-for-kuskokwim-300-sled-dog-race/

I mentioned the warmth in Bethel a few days ago, but it really is remarkable: since October 1, the total number of freezing degree days is easily the lowest in the modern record (1930-present).  As a reminder, freezing degree days are a simple measure of accumulated "freeze units"; we just sum up all positive daily differences between 32°F and the daily mean temperature.  So far this winter the freezing thermal units have amounted to less than 40% of the 1981-2010 normal for the same period.

The previous lowest FDD total for October 1 - January 15 was in winter 2000-2001, which turned out to be Bethel's warmest winter on record overall (November - March).  It was an analogous winter in some respects, with a weak La Niña and without a negative PDO phase to match.  The absence of a negative PDO this winter is the most obvious reason for the lack of colder weather that some of us expected to accompany the La Niña episode.

As another illustration of just how warm it's been in Bethel, consider that more days so far this winter (since November 1) have had a high temperature above freezing (37 days) than below freezing (32 days).  This too is unprecedented for 1930-present.