The salinity of the Arctic Ocean is at risk, a new model shows
DOE / LOS ALAMOS NATIONAL LABORATORY
IMAGE: DYE RELEASED FROM THE BEAUFORT GYRE REGION OF WESTERN PLASTIC INDICATES FRESHWATER TRANSPORT THROUGH THE CANADIAN ARCTIC ARCHIPELAGO TO THE WESTERN LABRADOR SEA. Show more CREDIT: FRANCESCA SAMSEL AND GREG ABRAM (UNIVERSITY OF TEXAS IN AUSTIN). HIGH-RESOLUTION VERSION LINKED HERE: HTTPS://WWW.DROPBOX.COM/S/8AD4665KZO5WM4X/FEATURED_IMAGE_HORIZONTAL.PNG?DL=0
LOS ALAMOS, NM, February 24, 2021 – The Beaufort Sea, the largest freshwater reservoir in the Arctic Ocean, has increased its freshwater content by 40 percent over the past two decades, endangering global climate patterns. A rapid release of this freshwater into the Atlantic could destroy the delicate climatic equilibrium that defines the global climate.
“A freshwater release of this size into the subpolar North Atlantic could impact a critical circulation pattern known as the Atlantic Meridional Overturning Circulation, which has a significant impact on the climate in the northern hemisphere,” said Wilbert Weijer, author of the Los Alamos National Laboratory Project.
A joint model study by Los Alamos researchers and staff from the University of Washington and NOAA looked at the mechanics of this scenario. The team first investigated an earlier release event between 1983 and 1995 and, using virtual dye tracers and numerical modeling, simulated the ocean circulation and tracked the propagation of the freshwater release.
“People have already spent a lot of time studying why the freshwater in the Beaufort Sea has gotten so high over the past few decades,” said lead author Jiaxu Zhang, who started work at the center for during her postdoctoral fellowship at Los Alamos National Laboratory nonlinear studies. She is now at the UW Cooperative Institute for Climate, Ocean and Ecosystem Studies. “But they rarely care where the freshwater goes, and we think that is a much more important problem.”
The study was the most detailed and sophisticated of its kind, providing numerical insights into the decrease in salinity in certain marine areas as well as the pathways of freshwater release. The experiment unexpectedly showed that most of the freshwater reached the North Atlantic (the Labrador Sea) via a narrow series of passages between Canada and Greenland known as the Canadian Archipelago.
The traditional view had mainly considered the transport of liquid fresh water in the form of sea ice over the Fram Strait (a passage between Greenland and Svalbard). The freshwater release has been shown to significantly reduce salinity in the Labrador Sea – a refreshment of 0.2 practical salinity units (psu) on western shelves and 0.4 psu locally in the Labrador Current.
However, the modeled release was based on past freshwater quantities from the 1990s. Now that volume is significantly larger, at over 23,300 cubic kilometers, due to an unusually sustained circulation pattern called the Beaufort Gyre and an unprecedented decline in sea ice. If this very large volume of freshwater is released into the North Atlantic, the impact could also be very large. The exact effect is still unknown. “Our study of the previous release event provides a picture of the potential impact of a future, larger release,” said Weijer.
The model used in the study was partly developed in Los Alamos. It is the Energy Exascale Earth System Model Version 0 (E3SMv0), which includes the LANL Parallel Ocean Program (POP) and the powerful sea ice model CICE.
“This work is a great example of Los Alamos’ innovative approaches to ocean modeling. and it also demonstrates the laboratory’s leadership role in high latitude climate science through projects such as the High Latitude Application and Testing of Earth System Models (HiLAT-RASM), ”said Weijer.
The paper: “Labrador Sea Refreshment Related to the Release of Beaufort Gyre Freshwater.” 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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