Decadal Freshening of the Antarctic Bottom Water Exported from the Weddell Sea

Loïc Jullion National Oceanography Centre, University of Southampton, Southampton, United Kingdom

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Alberto C. Naveira Garabato National Oceanography Centre, University of Southampton, Southampton, United Kingdom

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Michael P. Meredith British Antarctic Survey, Cambridge, and Scottish Association for Marine Science, Oban, United Kingdom

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Paul R. Holland British Antarctic Survey, Cambridge, United Kingdom

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Peggy Courtois National Oceanography Centre, University of Southampton, Southampton, United Kingdom

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Brian A. King National Oceanography Centre, Southampton, United Kingdom

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Abstract

Recent decadal changes in Southern Hemisphere climate have driven strong responses from the cryosphere. Concurrently, there has been a marked freshening of the shelf and bottom waters across a wide sector of the Southern Ocean, hypothesized to be caused by accelerated glacial melt in response to a greater flux of warm waters from the Antarctic Circumpolar Current onto the shelves of West Antarctica. However, the circumpolar pattern of changes has been incomplete: no decadal freshening in the deep layers of the Atlantic sector has been observed. In this study, the authors document a significant freshening of the Antarctic Bottom Water exported from the Weddell Sea, which is the source for the abyssal layer of the Atlantic overturning circulation, and trace its possible origin to atmospheric-forced changes in the ice shelves and sea ice on the eastern flank of the Antarctic Peninsula that include an anthropogenic component. These findings suggest that the expansive and relatively cool Weddell gyre does not insulate the bottom water formation regions in the Atlantic sector from the ongoing changes in climatic forcing over the Antarctic region.

Current affiliation: Geophysical Fluid Dynamics Institute, The Florida State University, Tallahassee, Florida.

Corresponding author address: Loïc Jullion, Geophysical Fluid Dynamics Institute, The Florida State University, Tallahassee, FL 32306. E-mail: l.jullion@fsu.edu

Abstract

Recent decadal changes in Southern Hemisphere climate have driven strong responses from the cryosphere. Concurrently, there has been a marked freshening of the shelf and bottom waters across a wide sector of the Southern Ocean, hypothesized to be caused by accelerated glacial melt in response to a greater flux of warm waters from the Antarctic Circumpolar Current onto the shelves of West Antarctica. However, the circumpolar pattern of changes has been incomplete: no decadal freshening in the deep layers of the Atlantic sector has been observed. In this study, the authors document a significant freshening of the Antarctic Bottom Water exported from the Weddell Sea, which is the source for the abyssal layer of the Atlantic overturning circulation, and trace its possible origin to atmospheric-forced changes in the ice shelves and sea ice on the eastern flank of the Antarctic Peninsula that include an anthropogenic component. These findings suggest that the expansive and relatively cool Weddell gyre does not insulate the bottom water formation regions in the Atlantic sector from the ongoing changes in climatic forcing over the Antarctic region.

Current affiliation: Geophysical Fluid Dynamics Institute, The Florida State University, Tallahassee, Florida.

Corresponding author address: Loïc Jullion, Geophysical Fluid Dynamics Institute, The Florida State University, Tallahassee, FL 32306. E-mail: l.jullion@fsu.edu
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