On the consumption of Antarctic Bottom Water in the abyssal ocean

de Lavergne, Casimir; Madec, Gurvan; Le Sommer, Julien; Nurser, A.J. George; Naveira Garabato, Alberto C.. 2016 On the consumption of Antarctic Bottom Water in the abyssal ocean. Journal of Physical Oceanography, 46 (2). 635-661. 10.1175/JPO-D-14-0201.1

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Text © Copyright 2016 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act September 2010 Page 2 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108, as revised by P.L. 94-553) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a web site or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. Additional details are provided in the AMS Copyright Policy, available on the AMS Web site located at (http://www.ametsoc.org/) or from the AMS at 617-227-2425 or copyrights@ametsoc.org. jpo-d-14-0201%2E1.pdf - Published Version Download (3MB) | Preview

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Text © 2015 American Meterological Society. Permission to place a copy of this work on this server has been provided by the AMS. The AMS does not guarantee that the copy provided here is an accurate copy of the published work. jpo-d-14-0201%2E1.pdf - Accepted Version Download (2MB) | Preview

Abstract/Summary

The abyssal ocean is primarily filled by cold, dense waters formed around Antarctica and collectively referred to as Antarctic Bottom Water (AABW). At steady state, AABW must be consumed in the ocean interior at the same rate it is produced, but how and where this consumption is achieved remains poorly understood. Here, we present estimates of abyssal water mass transformation by geothermal heating and parameterized internal wave-driven mixing. We use maps of the energy input to internal waves by tidal and geostrophic motions interacting with topography combined with assumptions about the distribution of energy dissipation to evaluate dianeutral transports induced by breaking internal tides and lee waves. Geothermal transformation is assessed based on a map of geothermal heat fluxes. Under the hypotheses underlying the constructed climatologies of buoyancy fluxes, we calculate that locally-dissipating internal tides and geothermal heating contribute respectively about 8 and 5 Sv of AABW consumption (upwelling), mostly north of 30°S. In contrast, parameterized lee wave-driven mixing causes significant transformation only in the Southern Ocean, where it forms about 3 Sv of AABW, decreasing the mean density but enhancing the northward flow of abyssal waters. The possible role of remotely-dissipating internal tides in complementing AABW consumption is explored based on idealized distributions of mixing energy. Depending mostly on the chosen vertical structure, such mixing could drive 1 to 28 Sv of additional AABW upwelling, highlighting the need to better constrain the spatial distribution of remote dissipation. Though they carry large uncertainties, these climatological transformation estimates shed light on the qualitative functioning and key unknowns of the diabatic overturning.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1175/JPO-D-14-0201.1
ISSN:	0022-3670
NORA Subject Terms:	Marine Sciences
Date made live:	28 Jan 2016 13:24 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/512784

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