Winter sea ice in the Bering Sea hit its lowest levels in thousands of years in 2018 and 2019, scientists reported in a new study. While much attention has been given to the rapid loss of summer ice in the Arctic Ocean and surrounding seas, the new research indicates that ice formation in the cold season is also being drastically reduced by rising global temperatures and shifting atmospheric and ocean circulation patterns.
“What we’ve seen most recently is unprecedented in the last 5,500 years,” Matthew Wooller, director of the Alaska Stable Isotope Facility and a coauthor of the paper, said in a statement. “We haven’t seen anything like this in terms of sea ice in the Bering Sea.”
Satellite data has allowed scientists to closely track sea ice extent over the past four decades. But for the new study, published in the journal Science Advances, researchers analyzed a peat core taken on St. Matthew Island, located in the middle of the Bering Sea in Alaska. Scientists were able to reconstruct atmospheric and ocean conditions dating back thousands of years by analyzing oxygen molecules from sediment and plant debris trapped within the peat. Talking to Reuters, Wooller described the peat core as a “book going back in time.”
Summertime sea ice in the Arctic is expected to hit its second-lowest extent this month in 40 years of satellite observation. Sea ice, however, typically builds up again each winter. The new study suggests this critical time for ice recovery has been compromised. The scientists also found that the changes in sea ice lag several decades behind changes in greenhouse gases. That means that the low ice extents being recorded today are the result of emissions from decades ago, and that ice loss is built into the system for decades to come.