How warm sea temperatures influence our fall weather

By Rick Thoman
Alaska Climate Specialist
Alaska Center for Climate Assessment and Preparedness
International Arctic Research Center/University of Alaska Fairbanks

Late summer sea surface temperatures all around the region were significantly higher than August 2024, and this will likely play a role in how autumn weather unfolds.
For the Bering Sea, last August was exceptionally stormy, which helped keep the upper oceans well mixed, instead of the usual shallow layer of warm water right near the surface. This resulted in heat being distributed through a greater depth of water than is usually the cause in August.
This August was more typical, with sea surface temperatures near to slightly above normal overall.
In the Chukchi Sea it was a different story. Last summer there was persistent sea ice off the northeast Chukotka coast, which at times drifted in the current down into the west side of the Bering Strait. That ice did eventually melt, but it took all of September and it kept southern Chukchi Sea temperatures colder than usual. The ice in this region melted “on schedule” this year, so August sea surface temperatures are much warmer than last year, with a fairly large area having temperatures more than 10ºF higher.
How will this impact autumn weather?
Most obviously, Chukchi Sea waters will very likely take longer to cool off enough to start to form sea ice, so freeze-up is likely to be later than last year. This is important because getting ice through the Bering Strait and down to St. Lawrence Island can't really get going until the Chukchi freezes.
The impacts of water waters in the Bering Sea are probably more subtle. August ocean temperatures are not likely to affect the timing of sea ice formation in Norton Sound or the Yukon River delta. However, warmer ocean waters will provide more water to storms that come along in the next couple of months, and so storms may well be wetter than they otherwise would have been just from increased evaporation from the ocean to the air.