Recent reduced abyssal overturning and ventilation in the Australian Antarctic Basin
Recent reduced abyssal overturning and ventilation in the Australian Antarctic Basin
Dense water formed near Antarctica, known as Antarctic bottom water (AABW), drives deep ocean circulation and supplies oxygen to the abyssal ocean. Observations show that AABW has freshened and contracted since the 1960s, yet the drivers of these changes and their impact remain uncertain. Here, using observations from the Australian Antarctic Basin, we show that AABW transport reduced by 4.0 Sv between 1994 and 2009, during a period of strong freshening on the continental shelf. An increase in shelf water salinity between 2009 and 2018, previously linked to transient climate variability, drove a partial recovery (2.2 Sv) of AABW transport. Over the full period (1994 to 2017), the net slowdown of −0.8 ± 0.5 Sv decade −1 thinned well-oxygenated layers, driving deoxygenation of −3 ± 2 μmol kg −1 decade −1. These findings demonstrate that freshening of Antarctic shelf waters weakens the lower limb of the abyssal overturning circulation and reduces deep ocean oxygen content.
537-544
Gunn, Kathryn L.
5952c101-ecf3-4b62-b817-86007cdc8ce4
Rintoul, Stephen R.
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England, Matthew H.
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Bowen, Melissa M.
f037bf68-dc36-450b-a93b-ce7f6f62cc50
Gunn, Kathryn L.
5952c101-ecf3-4b62-b817-86007cdc8ce4
Rintoul, Stephen R.
ff078a21-d6cd-45bf-8c8f-f81f2e8ae410
England, Matthew H.
16ad5d6a-b9df-49f9-ad79-174e890544ef
Bowen, Melissa M.
f037bf68-dc36-450b-a93b-ce7f6f62cc50
Gunn, Kathryn L., Rintoul, Stephen R., England, Matthew H. and Bowen, Melissa M.
(2023)
Recent reduced abyssal overturning and ventilation in the Australian Antarctic Basin.
Nature Climate Change, 13 (6), .
(doi:10.1038/s41558-023-01667-8).
Abstract
Dense water formed near Antarctica, known as Antarctic bottom water (AABW), drives deep ocean circulation and supplies oxygen to the abyssal ocean. Observations show that AABW has freshened and contracted since the 1960s, yet the drivers of these changes and their impact remain uncertain. Here, using observations from the Australian Antarctic Basin, we show that AABW transport reduced by 4.0 Sv between 1994 and 2009, during a period of strong freshening on the continental shelf. An increase in shelf water salinity between 2009 and 2018, previously linked to transient climate variability, drove a partial recovery (2.2 Sv) of AABW transport. Over the full period (1994 to 2017), the net slowdown of −0.8 ± 0.5 Sv decade −1 thinned well-oxygenated layers, driving deoxygenation of −3 ± 2 μmol kg −1 decade −1. These findings demonstrate that freshening of Antarctic shelf waters weakens the lower limb of the abyssal overturning circulation and reduces deep ocean oxygen content.
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s41558-023-01667-8
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Accepted/In Press date: 3 April 2023
e-pub ahead of print date: 25 May 2023
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Funding Information:
We thank the crews and science parties of the voyages used in this manuscript as well as B. Huber, A. Gordon and S. Dye for collecting high-quality, open-access hydrographic and mooring data. We thank the Consortium for Ocean-Sea Ice Modelling in Australia ( https://cosima.org.au/ ) for making the ACCESS-OM2 suite of models available. K.L.G., S.R.R. and M.H.E. are supported by the Centre for Southern Hemisphere Oceans Research. S.R.R. also receives support from the Antarctic Science Collaboration Initiative, through the Australian Antarctic Program Partnership. M.H.E. also receives support from the Australian Research Council, including the ARC Australian Centre for Excellence in Antarctic Science (ARC grant no. SR200100008). M.M.B. is supported by the New Zealand Strategic Science Investment Fund: Antarctic Science Platform Contract ANT1801.
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Local EPrints ID: 484289
URI: http://eprints.soton.ac.uk/id/eprint/484289
ISSN: 1758-678X
PURE UUID: e99b6619-300f-4ef5-9c55-17ca3ae03c24
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Date deposited: 13 Nov 2023 18:57
Last modified: 18 Mar 2024 04:16
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Author:
Kathryn L. Gunn
Author:
Stephen R. Rintoul
Author:
Matthew H. England
Author:
Melissa M. Bowen
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