Climate Watch
By Rick Thoman Alaska Climate Specialist Alaska Center for Climate Assessment and Policy International Arctic Research Center/University of Alaska Fairbanks
Ocean temperatures in the region are gradually cooling off, but with sea surface temperatures mostly in the 40s, we’re still some time away from sea ice.
The Chukchi Sea pack ice retreated to more than 450 miles northwest of Utqiaġvik at the end of September and first days of October but is now starting to grow and expand southward.
Unlike decades past, there is no old ice near the northern Chukotka coast to come south in the fall (the “blue icebergs” that Bering Strait elders remember). Nowadays, all the ice must be made afresh, and as a result it takes a long time for the heat accumulated during the summer to be dissipated out of the ocean surface water so that ice can form.
We know that the Chukchi Sea really needs to be mostly ice covered before we can get significant ice south of the Bering Strait, to and beyond St. Lawrence Island.
Sea ice formation follows a different process in Norton Sound and on the Alaska coast from the Yukon River delta southward. In Norton Sound, ice first forms in the brackish waters where rivers empty into the ocean. We’ve already seen that this month in Norton and Golovin Bays, though this early ice can be melted out if windy mild weather returns. A little later, ice will form in and just beyond the Yukon River delta and then build out westward. Because Norton Sound is much shallower than the Bering Strait, there is less heat stored in the water below the surface and so freeze-up can occur faster and is more weather dependent than in the open Chukchi Sea and Bering Strait, where the summer’s heat extends deeper into the ocean.
The latest seasonal sea ice forecast from NOAA’s Climate Prediction CentTeraskhoewsOicue tgrowing out from eastern Norton Sound in early November,Oreracdhiengrtshe Nome area the second half of the month, but for
443-8100 areas of open water to persist in the southern Chukchi into early December.