A new study published in the journal Science Advances says that researchers have determined that the extent of sea ice in the region of St. Matthew Island is lower than it has been for thousands of years.
Researchers reached their conclusions through analysis of vegetation on the small, uninhabited island, part of the Alaska Maritime National Wildlife Refuge.
Their report describes how a peat core rom St. Matthew Island, when analyzed for its chemical composition, identified plant remains from 5,500 years ago to the present, allowing for an estimate of how sea ice in the region has changed over all those years.
The study from the University of Alaska Fairbanks on Tuesday, Sept. 1, was also released in EurekAlert, the online publication of the American Association for the Advancement of Science.
Miriam Jones, a research geologist with the U.S. Geological Survey, and lead author of the study, said that the island has essentially been recording what’s happening in the ocean and atmosphere around it. Jones was formerly a faculty researcher at UAF.
“Our study did not investigate impacts to Bering Sea ecosystems, but the disappearing winter sea ice is the product of warming ocean and changing circulation patterns, which we suspect would lead to a change in marine ecosystem,” Jones said. “Our study is unique in that it shows sea ice changes in the Bering sea over the last 5,500 years, which stretches what we know about Bering Sea ice extent well beyond the period observed by satellites.”
By analyzing data from a model that tracks atmospheric movement using isotopic signatures of precipitation, researchers found that heavier precipitation originated from the North Pacific, while lighter precipitation originated from the Arctic.
Researchers at the University of Alaska Fairbanks’s Alaska Stable Isotope Facility analyzed isotope ratios throughout the peat layer samples, providing a time stamp for ice conditions that existed through the millennia.
According to Matthew Wooler, director of the Alaska Stable Isotope Facility, and a contributor to the study, their observations on sea ice in the Bering Sea are unprecedented over the last 5,500 years.
The long-term findings also affirm that reductions in Bering Sea ice are due to more than recent higher temperatures associated with global warming, Jones said. Atmospheric and ocean currents, which are also affected by climate change, play a larger role in the presence of sea ice, she said.
