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Horizontal mixing in the Southern Ocean from Argo float trajectories


Roach, CJ and Balwada, D and Speer, K, Horizontal mixing in the Southern Ocean from Argo float trajectories, Journal of Geophysical Research: Oceans, 121, (8) pp. 5570-5586. ISSN 2169-9275 (2016) [Refereed Article]


Copyright Statement

Copyright 2016 American Geophysical Union

DOI: doi:10.1002/2015JC011440


We provide the first observational estimate of the circumpolar distribution of cross‐stream eddy diffusivity at 1000 m in the Southern Ocean using Argo float trajectories. We show that Argo float trajectories, from the float surfacing positions, can be used to estimate lateral eddy diffusivities in the ocean and that these estimates are comparable to those obtained from RAFOS floats, where they overlap. Using the Southern Ocean State Estimate (SOSE) velocity fields to advect synthetic particles with imposed behavior that is "Argo‐like" and "RAFOS‐like" diffusivity estimates from both sets of synthetic particles agreed closely at the three dynamically very different test sites, the Kerguelen Island region, the Southeast Pacific Ocean, and the Scotia Sea, and support our approach. Observed cross‐stream diffusivities at 1000 m, calculated from Argo float trajectories, ranged between 300 and 2500 m2 s−1, with peaks corresponding to topographic features associated with the Scotia Sea, the Kerguelen Plateau, the Campbell Plateau, and the Southeast Pacific Ridge. These observational estimates agree with previous regional estimates from the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) near the Drake Passage, and other estimates from natural tracers (helium), inverse modeling studies, and current meter measurements. These estimates are also compared to the suppressed eddy diffusivity in the presence of mean flows. The comparison suggests that away from regions of strong topographic steering suppression explains both the structure and magnitude of eddy diffusivity but that eddy diffusivities in the regions of topographic steering are greater than what would be theoretically expected and the ACC experiences localized enhanced cross‐stream mixing in these regions.

Item Details

Item Type:Refereed Article
Keywords:Southern Ocean
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Physical oceanography
Objective Division:Environmental Management
Objective Group:Management of Antarctic and Southern Ocean environments
Objective Field:Antarctic and Southern Ocean oceanic processes
UTAS Author:Roach, CJ (Dr Christopher Roach)
ID Code:132285
Year Published:2016
Web of Science® Times Cited:15
Deposited By:Oceans and Cryosphere
Deposited On:2019-05-01
Last Modified:2019-06-20
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