Watson, AJ, Ledwell, JR, Messias, M-J et al. (5 more authors) (2013) Rapid cross-density ocean mixing at mid-depths in the Drake Passage measured by tracer release. Nature, 501 (7467). pp. 408-411. ISSN 0028-0836
Abstract
Diapycnal mixing (across density surfaces) is an important process in the global ocean overturning circulation1, 2, 3. Mixing in the interior of most of the ocean, however, is thought to have a magnitude just one-tenth of that required to close the global circulation by the downward mixing of less dense waters4. Some of this deficit is made up by intense near-bottom mixing occurring in restricted ‘hot-spots’ associated with rough ocean-floor topography5, 6, but it is not clear whether the waters at mid-depth, 1,000 to 3,000 metres, are returned to the surface by cross-density mixing or by along-density flows7. Here we show that diapycnal mixing of mid-depth (~1,500 metres) waters undergoes a sustained 20-fold increase as the Antarctic Circumpolar Current flows through the Drake Passage, between the southern tip of South America and Antarctica. Our results are based on an open-ocean tracer release of trifluoromethyl sulphur pentafluoride. We ascribe the increased mixing to turbulence generated by the deep-reaching Antarctic Circumpolar Current as it flows over rough bottom topography in the Drake Passage. Scaled to the entire circumpolar current, the mixing we observe is compatible with there being a southern component to the global overturning in which about 20 sverdrups (1 Sv = 106 m3 s−1) upwell in the Southern Ocean, with cross-density mixing contributing a significant fraction (20 to 30 per cent) of this total, and the remainder upwelling along constant-density surfaces. The great majority of the diapycnal flux is the result of interaction with restricted regions of rough ocean-floor topography.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2013 Macmillan Publishers Limited. This is an author produced version of a paper published in Nature. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | Physical oceanography |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Earth Surface Science Institute (ESSI) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 10 Aug 2016 14:15 |
Last Modified: | 16 Jan 2018 07:16 |
Published Version: | http://dx.doi.org/10.1038/nature12432 |
Status: | Published |
Publisher: | Nature Publishing Group |
Identification Number: | 10.1038/nature12432 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:90314 |