Convective and shear-induced turbulence in the deep Kane Gap

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Van Haren, H., Morozov, E., Gostiaux, Louis, Tarakanov, Roman
• Other Authors: Royal Netherlands Institute for Sea Research (NIOZ), P.P. Shirshov Institute of Oceanology (SIO), Russian Academy of Sciences Moscow (RAS), Laboratoire de Mecanique des Fluides et d'Acoustique (LMFA), École Centrale de Lyon (ECL), Université de Lyon-Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2013
• Subjects: [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph]; [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph]; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Antarctic; Kane; Antarc*
• Online Access: https://hal.archives-ouvertes.fr/hal-00880518; https://hal.archives-ouvertes.fr/hal-00880518/document; https://hal.archives-ouvertes.fr/hal-00880518/file/VANHAREN_JGR_2013.pdf; https://doi.org/10.1002/2013JC009282

International audience 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.