LOS ALAMOS, NM, February 24, 2021–The Beaufort Sea, the Arctic Ocean’s largest freshwater reservoir, has increased its freshwater content by 40 percent over the past two decades, threatening global climate patterns. A rapid release of this freshwater into the Atlantic Ocean could devastatingly disrupt the delicate climate balance that governs global climate.
“A freshwater release of this magnitude into the subpolar North Atlantic could affect a critical circulation pattern called the Atlantic Meridional Overturning Circulation, which has a significant impact on northern hemisphere climate,” said Wilbert Weijer, an author of the Los Alamos National Laboratory project .
A joint modeling study by Los Alamos researchers and collaborators from the University of Washington and NOAA delved into the mechanics surrounding this scenario. The team first studied an earlier release event that occurred between 1983 and 1995, and using virtual dye tracers and numerical modeling, the researchers simulated ocean circulation and tracked the spread of the freshwater release.
“People have already spent a lot of time investigating why the Beaufort Sea’s freshwater has risen so high over the past few decades,” said lead author Jiaxu Zhang, who began the work during her postdoctoral fellowship at Los Alamos National Laboratory at the Center for Nonlinear Studies. She is now at UW’s Cooperative Institute for Climate, Ocean and Ecosystem Studies. “But they rarely care about where the fresh water goes, and we think that’s a much more important issue.”
The study was the most detailed and sophisticated of its kind, providing numerical insight into salinity decreases in specific marine areas as well as pathways of freshwater release. The experiment unexpectedly showed that most freshwater reaches the North Atlantic (the Labrador Sea) through a narrow passage between Canada and Greenland called the Canadian Archipelago.
The traditional view had mainly considered the transport of liquid fresh water in the form of sea ice across the Fram Strait (a passage between Greenland and Svalbard). Freshwater release has been shown to significantly reduce salinity levels in the Labrador Sea – an increase of 0.2 practical salinity units (psu) on the western shelves and 0.4 psu locally in the Labrador Current.
However, the modeled clearance was based on past freshwater volumes from the 1990s. Now that volume is significantly larger, more than 23,300 cubic kilometers, due to an unusually persistent circulation pattern called the Beaufort Gyre and an unprecedented decline in sea ice. If this very large amount of fresh water ends up in the North Atlantic, the impact could be correspondingly large. The exact effects are still unknown. “Our study of the previous release event provides a picture of the potential impact of a future, larger release,” Weijer said.
The model used in the study was also partially developed at Los Alamos. It is the Energy Exascale Earth System Model Version 0 (E3SMv0) that includes LANL’s Parallel Ocean Program (POP) and its powerful sea ice model CICE.
“This work is a great example of Los Alamos’ innovative ocean modeling approaches and also demonstrates the lab’s leadership in high-latitude climate science through projects such as the High-Latitude Application and Testing of Earth Systems Models (HiLAT-RASM),” said Weijer.
The paper: “Refreshing of the Labrador Sea associated with freshwater release in the Beaufort-Gyre.” nature communication. Jiaxu Zhang, Wilbert Weijer, Michael Steele, Wei Cheng, Tarun Verma and Milena Veneziani. DOI 10.1038/s41467-021-21470-3
Funding: This research was funded by the US DOE Office of Science, a LANL LDRD Award, a CNLS Postdoc Fellowship Award, and NOAA.
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