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article imageBering Sea ice extent is at lowest in over 5,000 years

By Karen Graham     Sep 4, 2020 in Science
Fairbanks - Through the analysis of vegetation from a Bering Sea island, researchers have determined that the extent of sea ice in the region is lower than it’s been for thousands of years.
Without a doubt, the climate crisis has reshaped the Arctic, with one of the most dramatic events occurring in the winter of 2018, when the sea ice extent set the record for the least amount being recorded, dating back to 1850, according to NOAA data.
In 2019, there was a near-repeat of the record-breaking low sea ice extent as the Earth continued to sweat in unrelenting heat, making October 2019 the second-hottest October ever recorded, just behind 2015, while Arctic sea ice coverage shrank to its smallest size yet for October.
To explain what has been happening in the Bering Sea, scientists at the University of Alaska, Fairbanks have been studying the changes in sea ice extent due to the higher temperatures associated with global warming. The findings were published in the journal Science Advances on September 2, 2020.
Field camp on St. Matthew Island  Alaska  1984.
Field camp on St. Matthew Island, Alaska, 1984.
Angell Robert, U.S. Fish and Wildlife Service
The study describes how a peat core from an island in the middle of the Bering Sea - St. Matthew Island - is providing a look back in time, while providing an estimate of how sea ice in the region has changed dating back thousands of years.
"It's a small island in the middle of the Bering Sea, and it's essentially been recording what's happening in the ocean and atmosphere around it," said lead author Miriam Jones, a research geologist with the U.S. Geological Survey. Jones worked as a faculty researcher at the University of Alaska Fairbanks when the project began in 2012, reports Science Daily.
Two isotopes of Oxygen
There are three known stable isotopes of the element oxygen - oxygen-16, oxygen-17, and oxygen-18.. The ancient sea ice record can be ascertained by analysing the changes in the relative amounts of two isotopes — oxygen-16 and oxygen-18.
Main isotopes of oxygen
Main isotopes of oxygen
NASA
According to the study, the ratio of these two isotopes changes depending on patterns in the atmosphere and ocean, reflecting the different signatures that precipitation has around the globe. More oxygen-18 makes for an isotopically “heavier” precipitation, more oxygen-16 makes precipitation “lighter.”
Using a model that tracks atmospheric movement using the isotopic signature of precipitation, the researchers found that heavier precipitation originated from the North Pacific, while lighter precipitation originated from the Arctic. What does this mean, you may ask?
View of Saint Matthew Island  Bering Sea  Alaska  taken on  April 16  2007 by David Hyrenbach  BEST ...
View of Saint Matthew Island, Bering Sea, Alaska, taken on April 16, 2007 by David Hyrenbach, BEST Project Office, NSF.
NOAA/NSF Bering Sea Ice Expedition
A "heavy" ratio means there is a seasonal pattern that causes a decrease in the amount sea ice, while a "light" ratio signals just the opposite, a season with more sea ice. This connection was confirmed though sea ice satellite data collected since 1979.
UAF’s Alaska Stable Isotope Facility analyzed isotope ratios throughout the peat layers, providing a time stamp for ice conditions that existed through the millennia.
The study concludes that modern ice conditions are at remarkably low levels, based on the isotopic history. “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 to Earther. “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.”
More about Bering sea, sea ice extent, over 5000 years, St Matthew Island, isotopes of oxygen
 
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