Significant increase in freshwater entering Arctic Ocean through Bering Strait

August 26, 2022

A new study has confirmed that over the past 30 years the volume of freshwater flowing through Bering Strait into the Arctic Ocean has increased by 40-50%, which means that the Arctic Ocean is becoming less salty. This could impact sea ice formation, regional and global ocean circulation, and ecosystems.

“Our analysis indicates that the Arctic Ocean is becoming less salty in part because the water flowing north through the Bering Strait is becoming less salty,” said lead author Lee Cooper of the University of Maryland Center for Environmental Science. “This could have a lot of downstream implications for how the Arctic Ocean works and connects with climate and related processes, including the intensity of mixing in the North Atlantic.”   

Researchers used a new tracer approach to look at the oxygen isotope composition of water samples collected throughout the Bering and Chukchi shelves to assess the change in saltiness. The study evaluated more than one thousand water samples collected over the extensive continental shelf and the results provide a strong confirmation of increasing freshwater. The significance of the Bering Strait for freshwater is that it is the single largest point source of freshwater to the Arctic Ocean.

Less saline water is quicker to freeze and less likely to mix with deep water, resulting in less nutrient-rich deeper water being upwelled, ultimately decreasing biological productivity. Ultimately it also may interfere with deep water mixing in the North Atlantic that is climate-sensitive. 

The study, “Changes in the oxygen isotope composition of the Bering Sea contribution to the Arctic Ocean are an independent measure of increasing freshwater fluxes through the Bering Strait”, authored by Lee Cooper and Jacqueline Grebmeier of the University of Maryland Center for Environmental Science and Cédric Magen of the University of Maryland, is part of a group of papers published as a special issue in PLOS One focused on the internationally coordinated Distributed Biological Observatory, supported by the US National Science Foundation, the US National Oceanic and Atmospheric Administration, NASA and other agencies, as well as science agencies in Korea, China, Japan, and Canada.