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Mixing on the continental slope of the southern Weddell Sea

Daae, Kjersti L.; Fer, Ilker; Abrahamsen, E. Povl. 2009 Mixing on the continental slope of the southern Weddell Sea. Journal of Geophysical Research, 114 (C09), C09018. 13, pp. 10.1029/2008JC005259

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Abstract/Summary

Shipboard hydrography and current profiles collected in 2003 and time series from moored current meters deployed in late 1990s are analyzed to study the variability of mixing in the southeastern Weddell Sea. Profiles of eddy diffusivity Kρ are inferred from finescale shear (vertical derivative of horizontal velocity) and strain (vertical derivative of isopycnal displacement) variance using parameterizations which relate the internal wave energy to the dissipation rate at small scales. The highest mixing rates are seen near the bottom where the eddy diffusivities are elevated by one order of magnitude from those in the interior and exceed 10^−4 m^2 s^−1. The observations show latitudinal variability in Kρ, particularly near the bottom, where Kρ significantly increases near 74° 28' S, the critical latitude for lunar semi-diurnal (M2) tides. In this region, the critical latitude coincides with near-critical topography on the upper continental slope, a situation which favors generation of M2 internal waves. Consistent with the results from finescale shear and strain parameterizations, which indicate highest bottom diffusivities near the critical latitude, independent analysis of current time series from moored instruments shows a thickening of the frictional bottom boundary layer near the critical latitude. Semidiurnal tidal dynamics at the upper continental slope together with the critical latitude effects lead to mixing that might significantly affect the regional heat budget and the circulation in the study area.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1029/2008JC005259
Programmes: BAS Programmes > Global Science in the Antarctic Context (2005-2009) > Antarctic Climate and the Earth System
ISSN: 0148-0227
Additional Keywords: turbulence, mixing, Weddell Sea, microstructure, finescale parameterization
NORA Subject Terms: Marine Sciences
Earth Sciences
Date made live: 11 Feb 2010 14:48
URI: http://nora.nerc.ac.uk/id/eprint/7616

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