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

Naveira Garabato, Alberto C, Frajka-Williams, Eleanor, Spingys, Carl P, Legg, Sonya, Polzin, Kurt L, Forryan, Alexander, Abrahamsen, Povl, Buckingham, Christian, Griffies, Stephen M, McPhail, Stephen, Nicholls, Keith, Thomas, Leif N and Meredith, Michael. 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. https://doi.org/10.1073/pnas.1904087116

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Abstract/Summary

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.

Item Type: Publication - Article
Digital Object Identifier (DOI): https://doi.org/10.1073/pnas.1904087116
ISSN: 00278424
Additional Keywords: ocean mixing, overturning circulation, submesoscale instabilities, turbulence
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Date made live: 20 Jun 2019 12:54 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/520649

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