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Mixing variability in the Southern Ocean

Citation

Meyer, A and Sloyan, BM and Polzin, KL and Phillips, H and Bindoff, NL, Mixing variability in the Southern Ocean, Journal of Physical Oceanography, 45, (4) pp. 966-987. ISSN 0022-3670 (2015) [Refereed Article]


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DOI: doi:10.1175/JPO-D-14-0110.1

Abstract

A key remaining challenge in oceanography is the understanding and parameterization of small-scale mixing. Evidence suggests that topographic features play a significant role in enhancing mixing in the Southern Ocean. We use 914 high-resolution hydrographic profiles from novel EM-APEX profiling floats to investigate turbulent mixing north of the Kerguelen Plateau, a major topographic feature in the Southern Ocean. We apply a shear-strain finescale parameterization to estimate diapycnal diffusivity in the upper 1600m of the ocean. Our indirect estimates of mixing match direct microstructure profiler observations made simultaneously. We find that mixing intensities have strong spatial and temporal variability, ranging from O(10-􀀀6) m2 s􀀀-1 to O(10􀀀-3) m2 s-􀀀1. We identify the topographic roughness, the current speed, and the wind speed as the main factors controlling mixing intensity. Additionally, we find strong regional variability in mixing dynamics and enhanced mixing in the Antarctic Circumpolar Current frontal region. This enhanced mixing is attributed to dissipating internal waves generated by the interaction of the Antarctic Circumpolar Current and the topography of the Kerguelen Plateau. Extending our mixing observations from the Kerguelen region to the entire Southern Ocean, we infer a large water mass transformation rate of 17 Sv (1 Sv = 106m3s􀀀-1) across the boundary of Antarctic Intermediate Water and Upper Circumpolar Deep Water in the Antarctic Circumpolar Current. This work suggests that the contribution of mixing to the Southern Ocean overturning circulation budget is particularly significant in fronts.

Item Details

Item Type:Refereed Article
Keywords:Southern Ocean, mixing, internal waves, EM-APEX, SOFINE, Kerguelen, Antarctic Circumpolar Current, ACC
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Physical Oceanography
Objective Division:Environment
Objective Group:Climate and Climate Change
Objective Field:Climate Variability (excl. Social Impacts)
UTAS Author:Meyer, A (Dr Amelie Meyer)
UTAS Author:Phillips, H (Dr Helen Phillips)
UTAS Author:Bindoff, NL (Professor Nathan Bindoff)
ID Code:99057
Year Published:2015
Funding Support:Australian Research Council (DP0877098)
Web of Science® Times Cited:14
Deposited By:IMAS Research and Education Centre
Deposited On:2015-03-12
Last Modified:2017-11-01
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