Climate Watch
By Rick Thoman Alaska Climate Specialist Alaska Center for Climate Assessment and Policy International Arctic Research Center/University of Alaska Fairbanks
Sea ice conditions in the northern Bering Sea looked promising: Cold weather starting in late October and a very cold November without any major storms set the sea ice early. Mid-winter brought a wide variety of weather, including excessive precipitation in December but that was followed by drier than average conditions after New Year’s Day. Even the sustained strong winds in early February only slightly moved ice around. However, all that unraveled during late February and early March as persistent east winds opened up large areas of open water,
especially between the Yukon Delta and St. Lawrence Island and in much of Norton Sound.
There were some hints that all was
not well with Bering Sea ice. Despite very favorable conditions for ice
growth and spread during the autumn and early winter, the ice pack was only at St. Paul about a week before retreating north —as recently as 2013 sea ice was at or beyond St. Paul for three months.
Satellite based sea ice thickness estimates in early February indicated that sea ice in much of the Bering Sea was thinner than last winter. The graphic highlights areas that had open water (less than 15 percent sea ice concentration) on one or more days in early March in the daily high-resolution satellite derived sea ice concentration dataset.
While much of this area that had open water has seen new ice growth with the turn to colder weather in recent days, it’s too late in the season for this new ice to approach the thickness and consistency of ice that formed months ago and can be expected to melt out much earlier than otherwise would have been the case. It’s not entirely clear what happened that resulted in this early appearance of open water. The frequent strong east winds likely contributed, and all the precipitation in December may have been a factor in insulating the ice. It may very well be that ocean water under the ice was warmer than might have been expected past on just the end of summer surface temperatures. Regardless of the combination of causes, it’s yet another sign our environment is changing right before our eyes.