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Journal Articles Journal of Geophysical Research. Oceans Year : 2013

Convective and shear-induced turbulence in the deep Kane Gap

Abstract

The boundary layer above a 4569 m deep slope in the near-equatorial N-Atlantic Ocean Kane Gap, a through-flow for Antarctic Bottom Water (AABW), is characterized by two distinct turbulent regimes that differ by an order of magnitude in intensity depending on the direction of through-flow. During south- and downward flow, vertical mixing is vigorous (resulting for a representative case-study in two-day mean and 6-132 m above the bottom averaged dissipation rate of ε = 2.1±1×10-9 W kg-1 and eddy diffusivity of Kz = 7±4×10-4 m2 s-1). The mixing is across relatively large vertical overturns. During north- and upward flow, smaller overturns are more horizontal as in stratified shear flow (with representative two-day mean ε = 6±3×10-11 W kg-1, Kz = 4±2×10-5 m2 s-1). Stratification is approximately the same during both flow-directions. Although the different turbulence regimes are partially associated with frictional boundary layers of large-scale flows above sloping topography, but not with those over flat bottoms, and partially with flow across a hill-promontory, internal waves are a dominant process in promoting turbulence. In addition, internal waves are observed to push stratification towards the bottom thereby importantly contributing to the mixing of AABW.
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Dates and versions

hal-00880518 , version 1 (13-04-2016)

Identifiers

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H. van Haren, E. Morozov, Louis Gostiaux, Roman Tarakanov. Convective and shear-induced turbulence in the deep Kane Gap. Journal of Geophysical Research. Oceans, 2013, 118 (11), pp.5924-5930. ⟨10.1002/2013JC009282⟩. ⟨hal-00880518⟩
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