Bering Sea Ice Hasn’t Been This Low in at Least 5,500 Years

Bering Sea Ice Hasn’t Been This Low in at Least 5,500 Years

The Arctic has seen some weird happenings as the climate crisis reshapes the region, but among the most dramatic was what happened in winter 2018 in the Bering Sea. Despite the inky black days, ice began to peel back from the coast in February. By May, the sea ice cover was basically completely gone a month ahead of schedule.

That alone is disturbing enough, but new research shows the event was even more bizarre than we thought. According to the findings, published in Science Advances on Wednesday, the Bering Sea hasn’t seen a winter like 2018 in at least 5,500 years. The study also shows that the world may have locked in irreversible changes that will leave the sea completely ice-free this century.

Miriam Jones, a paleoclimate researcher at the U.S. Geological Survey, led the new research, but it came about thanks to a whole other line of inquiry. St. Matthew Island sits smack dab in the middle of the Bering Sea and is home to a population of Arctic foxes. David Klein, an emeritus professor at the University of Alaska, Fairbanks, had been studying the foxes and their impact on the island’s bird population for years, occasionally hitching a ride to the island with wildlife managers from the Alaska Maritime National Wildlife Refuge.

The island’s location makes it a perfect place to get a long-term history of the area’s weather by taking samples of the peat-rich soil. Jones convinced Klein to take samples in 2012 when he went out with wildlife managers for their five-year bird survey and again in 2018.

“It’s essentially like a little weather station,” Jones said. “It’s just sitting in the middle of the Bering Sea recording what’s going on all around it.”

Jones analysed those cores for levels of a certain isotope of oxygen that can tell researchers about conditions around that location. They compared it to data on sea ice and found that high concentrations of the isotope were common with low levels of sea ice. The highest concentrations were found in 2018, the year with the lowest sea ice. Using that information, she reconstructed 5,500 years of climate over the region and found nothing that stacked up to 2018’s bizarre behaviour.

“The loss of winter sea ice is pretty alarming, because you expect the ice to be there in the wintertime and be there pretty reliably,” she said. “That’s what’s so shocking for 2018, and it created a lot of problems for Indigenous communities that live along the Bering Sea and rely on that sea ice to fish. With the lack of sea ice with big storms coming out of Pacific, there was also a lot of coastal erosion happening that was also impacting these coastal communities.”

No reflective sea ice also means the dark oceans can absorb more heat as the Sun does come up, locking in further changes for the region already under siege. Climate change has increased the odds of major summer Arctic cyclones — themselves a huge threat to sea ice — and warm water is seeping up from lower latitudes in both the Pacific and Atlantic sides of the region, stirring the ecological pot in ways scientists are racing to understand. Wildfires, rapid heating on land, and basically everything else are also creating unprecedented conditions for sea ice and the region at-large.

“This study gives us an appreciation for how far outside of the norm the recent conditions represent,” Seth Danielson, an ocean researcher at the University of Alaska, Fairbanks, said in an email. “As temperatures continue to rise, we are entering a realm that lacks prior analogues so we likely do not well understand the full ramifications for the ecosystem.”

Perhaps the most shocking part of Jones and her team’s analysis is the tie between Bering sea ice and carbon dioxide. The group looked at how well the sea ice trends mirrored carbon dioxide levels in the atmosphere and found there was a 100-year lag with how sea ice reacted to changing carbon dioxide. By looking at the more distant past sea ice and then what’s happened after the huge glug of carbon pollution humans have dumped in the atmosphere, the results suggest that it’s possible today’s sea ice is coming into equilibrium with carbon dioxide levels from 100 years ago.

“The alarming potential conclusion from this is that sea ice in 2018 is responding to warming conditions from previous decades,” Jones said. “And so if we just extrapolate that relationship, we essentially already locked in a complete loss of winter sea ice in the Bering Sea.”

The best-case scenario is that winter sea ice has adjusted to the rapid rise in emissions while still trending downward. Instead of a rapid loss of winter ice in the coming few decades, it could be completely lost by the end of the century if we don’t get our act together. So uh, we might want to do that.

Update, 3/9/20, 4:40 a.m. AEST: This post has been updated with comments from Seth Danielson.

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