Arctic & Antarctica
This spring, temperatures in Alaska and northern Canada have been significantly higher than usual. (Red indicates areas warmer than average while blue indicates colder than average. The darker the red, or blue, the greater the deviation from average.) Image by NASA Earth Observatory

Alaska's Bering Sea is feeling the effects of warm winters

This year in Alaska, an abnormal rise in temperature has, like in much of the north, disrupted communities and the environment

The Bering Sea and its coastal communities are feeling the effects of a pair of recent warm winters. Biologists and others who are following the changes closely are still working to understand what the long-term consequences might be.

"There is an ecosystem-wide shift in the northern Bering Sea," said biologist Gay Sheffield, of Nome, speaking during the Alaska Eskimo Whaling Commission meeting in Utqiagvik this week.

Sheffield initially had been billed as speaking on research from the region, but said she'd like to focus instead on the recent winters and other trends in her area.

The winter of 2018 was very, very warm, she said.

"We thought that was so strange. That couldn't possibly happen again," she said.

But then, it did. This year was comparably warm and that's important for a number of reasons. First of all, there's sea surface temperature. When there's less sea ice, there's less reflective surface and more dark water absorbing the heat.

"We have the sun. We just don't have ice," she said. "And the sun is very strong in the spring. And instead of melting the ice, it's just heating the water."

There's been a spike in sea surface temperatures in recent years, with the majority of the 10 warmest sea surface temperatures since 1900 happening in the last decade.

Departures from normal temperatures are also staggering, she said. For example, the water outside Kotzebue reached 12 to 14 degrees Fahrenheit higher than normal this year.

"In the past, the way people used to talk about sea surface temperature is you would have an anomalous year if the temperature was 3 degrees above normal," she said.

These enormous departures have left many scratching their heads about what the long-term effects could be.

Then, there's the sea floor temperatures. The northern Bering Sea is complex in that there tend to be cooler temperatures away from the coast, with warmer water along the coast. That warm water is often a result of outflow from mainland rivers, she explained.

The very cold water favors small, fatty cold water fish that feed seabirds, seals, whales and more. The warmer water favors the larger fish popular in the commercial fisheries of the Bering Sea.

In a nutshell, the lack of sea ice means the cooler channel away from the coast isn't cooling as much as it historically has. So, there's less difference between the near-coastal waters and the more central waters. Both are warmer than usual.

These changes seem to be heralding population spikes and downturns for a number of species. The largest increases have been seen in larger predatory species, like walleye pollock and Pacific cod, while the decreases have been more pronounced in the small, fatty forage species.

"This has had dramatic effects," she said.

As Sheffield discussed other observations people in Nome and throughout the region have made this winter, spring and early summer, many audience members nodded in agreement.

She talked about the seabird die-offs that have happened across the state, and the unusual stranding and mortality events with seals and other marine mammals in recent years.

"We don't know what happens next," she said. But she, and others who spoke at the conference, stressed the importance of trying to find out what's going on and how to deal with it.

The Sounder will continue to bring you coverage from the Alaska Eskimo Whaling Commission meeting.

See Arctic Sounder article . . .

See also Feeling the Heat in Winter