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Stabilization of dense Antarctic water supply to the Atlantic Ocean overturning circulation

Stabilization of dense Antarctic water supply to the Atlantic Ocean overturning circulation
Stabilization of dense Antarctic water supply to the Atlantic Ocean overturning circulation

The lower limb of the Atlantic overturning circulation is resupplied by the sinking of dense Antarctic Bottom Water (AABW) that forms via intense air–sea–ice interactions next to Antarctica, especially in the Weddell Sea1. In the last three decades, AABW has warmed, freshened and declined in volume across the Atlantic Ocean and elsewhere2–7, suggesting an ongoing major reorganization of oceanic overturning8,9. However, the future contributions of AABW to the Atlantic overturning circulation are unclear. Here, using observations of AABW in the Scotia Sea, the most direct pathway from the Weddell Sea to the Atlantic Ocean, we show a recent cessation in the decline of the AABW supply to the Atlantic overturning circulation. The strongest decline was observed in the volume of the densest layers in the AABW throughflow from the early 1990s to 2014; since then, it has stabilized and partially recovered. We link these changes to variability in the densest classes of abyssal waters upstream. Our findings indicate that the previously observed decline in the supply of dense water to the Atlantic Ocean abyss may be stabilizing or reversing and thus call for a reassessment of Antarctic influences on overturning circulation, sea level, planetary-scale heat distribution and global climate2,3,8.

1758-678X
742-746
Abrahamsen, E. Povl
fedecbff-9554-480b-a743-8ecf32fdb2f7
Meijers, Andrew J.S.
747ecd45-cdbe-47be-b952-4b724096f9d5
Polzin, Kurt L.
2424c950-d9b0-471c-95c0-b7b9d44132a1
Naveira Garabato, Alberto C.
97c0e923-f076-4b38-b89b-938e11cea7a6
King, Brian A.
960f44b4-cc9c-4f77-b3c8-775530ac0061
Firing, Yvonne L.
2518c141-9864-4b97-a9ed-adbab90dca66
Sallée, Jean Baptiste
286cb991-56c7-4468-92a7-860a23aeed7a
Sheen, Katy L.
2f10528e-d850-4a20-8685-5315605dd0cc
Gordon, Arnold L.
17579e7b-ea0c-4eeb-bab3-2cab03d701a7
Huber, Bruce A.
b759efb4-5f25-4c5f-80cf-fc707d687299
Meredith, Michael P.
25fd5f1c-f3ed-40a2-af59-5a7074a25fcd
Abrahamsen, E. Povl
fedecbff-9554-480b-a743-8ecf32fdb2f7
Meijers, Andrew J.S.
747ecd45-cdbe-47be-b952-4b724096f9d5
Polzin, Kurt L.
2424c950-d9b0-471c-95c0-b7b9d44132a1
Naveira Garabato, Alberto C.
97c0e923-f076-4b38-b89b-938e11cea7a6
King, Brian A.
960f44b4-cc9c-4f77-b3c8-775530ac0061
Firing, Yvonne L.
2518c141-9864-4b97-a9ed-adbab90dca66
Sallée, Jean Baptiste
286cb991-56c7-4468-92a7-860a23aeed7a
Sheen, Katy L.
2f10528e-d850-4a20-8685-5315605dd0cc
Gordon, Arnold L.
17579e7b-ea0c-4eeb-bab3-2cab03d701a7
Huber, Bruce A.
b759efb4-5f25-4c5f-80cf-fc707d687299
Meredith, Michael P.
25fd5f1c-f3ed-40a2-af59-5a7074a25fcd

Abrahamsen, E. Povl, Meijers, Andrew J.S., Polzin, Kurt L., Naveira Garabato, Alberto C., King, Brian A., Firing, Yvonne L., Sallée, Jean Baptiste, Sheen, Katy L., Gordon, Arnold L., Huber, Bruce A. and Meredith, Michael P. (2019) Stabilization of dense Antarctic water supply to the Atlantic Ocean overturning circulation. Nature Climate Change, 9, 742-746. (doi:10.1038/s41558-019-0561-2).

Record type: Letter

Abstract

The lower limb of the Atlantic overturning circulation is resupplied by the sinking of dense Antarctic Bottom Water (AABW) that forms via intense air–sea–ice interactions next to Antarctica, especially in the Weddell Sea1. In the last three decades, AABW has warmed, freshened and declined in volume across the Atlantic Ocean and elsewhere2–7, suggesting an ongoing major reorganization of oceanic overturning8,9. However, the future contributions of AABW to the Atlantic overturning circulation are unclear. Here, using observations of AABW in the Scotia Sea, the most direct pathway from the Weddell Sea to the Atlantic Ocean, we show a recent cessation in the decline of the AABW supply to the Atlantic overturning circulation. The strongest decline was observed in the volume of the densest layers in the AABW throughflow from the early 1990s to 2014; since then, it has stabilized and partially recovered. We link these changes to variability in the densest classes of abyssal waters upstream. Our findings indicate that the previously observed decline in the supply of dense water to the Atlantic Ocean abyss may be stabilizing or reversing and thus call for a reassessment of Antarctic influences on overturning circulation, sea level, planetary-scale heat distribution and global climate2,3,8.

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Accepted/In Press date: 25 July 2019
e-pub ahead of print date: 2 September 2019
Published date: 2 September 2019

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Local EPrints ID: 434793
URI: http://eprints.soton.ac.uk/id/eprint/434793
ISSN: 1758-678X
PURE UUID: 025ff054-148a-4aa5-bd73-5bfa2fe28c6e

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Date deposited: 09 Oct 2019 16:30
Last modified: 07 Oct 2020 06:39

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Contributors

Author: E. Povl Abrahamsen
Author: Andrew J.S. Meijers
Author: Kurt L. Polzin
Author: Brian A. King
Author: Yvonne L. Firing
Author: Jean Baptiste Sallée
Author: Katy L. Sheen
Author: Arnold L. Gordon
Author: Bruce A. Huber
Author: Michael P. Meredith

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