Temperature fluctuations and current shear in Antarctic Bottom Water at the Vema Sill |
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Authors: | Walter Zenk |
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Institution: | aIFM-GEOMAR, Leibniz-Institut für Meereswissenschaften an der Universität Kiel, Düsternbrooker Weg 20, D-24105 Kiel, Germany |
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Abstract: | The Vema Channel acts as a major conduit for the equatorward spreading of Antarctic Bottom Water between the Argentine and Brazil Basins. For almost two years the thermal stratification above its saddle depth (4660 m) – called Vema Sill – was recorded by moored thermistors and current meters. The lowest 490 m of the water column was instrumented to monitor the well-developed benthic boundary layer of Antarctic Bottom Water. The latter can be subdivided into Weddell Sea Deep Water on the sea bed and lower Circumpolar Deep Water above it. The data show fluctuations on various scales including periods, each about 1–2 weeks long, when the abyssal stratification virtually disappeared. Assuming a stable ratio between density and temperature, time series of bulk Richardson numbers are estimated from temperature and current shear data. The results suggest a potential for intermittent episodes of locally generated vertical mixing. |
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Keywords: | Antarctic Bottom Water Richardson numbers Argentine Basin Rio Grande Rise Vema Channel Vema Sill |
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