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Rapid mixing and exchange of deep-ocean waters in an abyssal boundary current

Rapid mixing and exchange of deep-ocean waters in an abyssal boundary current
Rapid mixing and exchange of deep-ocean waters in an abyssal boundary current
The overturning circulation of the global ocean is critically shaped by deep-ocean mixing, which transforms cold waters sinking at high latitudes into warmer, shallower waters. The effectiveness of mixing in driving this transformation is jointly set by two factors: the intensity of turbulence near topography and the rate at which well-mixed boundary waters are exchanged with the stratified ocean interior. Here, we use innovative observations of a major branch of the overturning circulation—an abyssal boundary current in the Southern Ocean—to identify a previously undocumented mixing mechanism, by which deep-ocean waters are efficiently laundered through intensified near-boundary turbulence and boundary–interior exchange. The linchpin of the mechanism is the generation of submesoscale dynamical instabilities by the flow of deep-ocean waters along a steep topographic boundary. As the conditions conducive to this mode of mixing are common to many abyssal boundary currents, our findings highlight an imperative for its representation in models of oceanic overturning.
0027-8424
13233-13238
Naveira Garabato, Alberto C.
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Frajka-williams, Eleanor E.
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Spingys, Carl P.
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Legg, Sonya
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Polzin, Kurt L.
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Forryan, Alexander
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Abrahamsen, E. Povl
fedecbff-9554-480b-a743-8ecf32fdb2f7
Buckingham, Christian E.
dba7c776-a8c6-4617-ad40-7919dd4ab3dc
Griffies, Stephen M.
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Mcphail, Stephen D.
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Nicholls, Keith W.
b89f0b06-278b-4666-9049-c0ba9c9960a6
Thomas, Leif N.
d071b068-5666-4a43-a885-fea71487f935
Meredith, Michael P.
25fd5f1c-f3ed-40a2-af59-5a7074a25fcd
Naveira Garabato, Alberto C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Frajka-williams, Eleanor E.
da86044e-0f68-4cc9-8f60-7fdbc4dc19cb
Spingys, Carl P.
8afecaad-9a5a-4713-949c-b47501498363
Legg, Sonya
0776c349-d632-4db5-ba26-8348473cddae
Polzin, Kurt L.
2424c950-d9b0-471c-95c0-b7b9d44132a1
Forryan, Alexander
55d366ed-42ab-4b4e-8a2c-b00959ecc823
Abrahamsen, E. Povl
fedecbff-9554-480b-a743-8ecf32fdb2f7
Buckingham, Christian E.
dba7c776-a8c6-4617-ad40-7919dd4ab3dc
Griffies, Stephen M.
bcc53ed0-1893-46cf-ac21-56259f8722f6
Mcphail, Stephen D.
58ac4bcd-26a6-4845-8e81-6d6a8f18aed7
Nicholls, Keith W.
b89f0b06-278b-4666-9049-c0ba9c9960a6
Thomas, Leif N.
d071b068-5666-4a43-a885-fea71487f935
Meredith, Michael P.
25fd5f1c-f3ed-40a2-af59-5a7074a25fcd

Naveira Garabato, Alberto C., Frajka-williams, Eleanor E., Spingys, Carl P., Legg, Sonya, Polzin, Kurt L., Forryan, Alexander, Abrahamsen, E. Povl, Buckingham, Christian E., Griffies, Stephen M., Mcphail, Stephen D., Nicholls, Keith W., Thomas, Leif N. and Meredith, Michael P. (2019) Rapid mixing and exchange of deep-ocean waters in an abyssal boundary current. Proceedings of the National Academy of Sciences, 116 (27), 13233-13238. (doi:10.1073/pnas.1904087116).

Record type: Article

Abstract

The overturning circulation of the global ocean is critically shaped by deep-ocean mixing, which transforms cold waters sinking at high latitudes into warmer, shallower waters. The effectiveness of mixing in driving this transformation is jointly set by two factors: the intensity of turbulence near topography and the rate at which well-mixed boundary waters are exchanged with the stratified ocean interior. Here, we use innovative observations of a major branch of the overturning circulation—an abyssal boundary current in the Southern Ocean—to identify a previously undocumented mixing mechanism, by which deep-ocean waters are efficiently laundered through intensified near-boundary turbulence and boundary–interior exchange. The linchpin of the mechanism is the generation of submesoscale dynamical instabilities by the flow of deep-ocean waters along a steep topographic boundary. As the conditions conducive to this mode of mixing are common to many abyssal boundary currents, our findings highlight an imperative for its representation in models of oceanic overturning.

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Accepted/In Press date: 26 May 2019
e-pub ahead of print date: 18 June 2019

Identifiers

Local EPrints ID: 433389
URI: https://eprints.soton.ac.uk/id/eprint/433389
ISSN: 0027-8424
PURE UUID: bbfdee7d-177d-47af-aebb-d28eec535f59
ORCID for Eleanor E. Frajka-williams: ORCID iD orcid.org/0000-0001-8773-7838

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Date deposited: 16 Aug 2019 16:30
Last modified: 17 Aug 2019 00:34

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