Seasonal variation of the Antarctic Slope Front occurence and position estimated from an interpolated hydrographic climatology

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  • 1 Sorbonne Universités, UPMC Univ., Paris 06, UMR 7159, LOCEAN-IPSL F-75005, Paris, France.
  • 2 Sorbonne Universités, UPMC Univ., Paris 06, UMR 7159, LOCEAN-IPSL F-75005, Paris, France.
  • 3 GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany.
  • 4 Aix-Marseille Université, CNRS/INSU, Université de Toulon, IRD, Mediterranean Institute of Oceanography (MIO) UM 110, Marseille, France.
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Abstract

The Antarctic Slope Front (ASF) is a fundamental feature of the subpolar Southern Ocean that is still poorly observed. In this study we build a statistical climatology of the temperature and salinity fields of the upper 380 m of the Antarctic margin. We use a comprehensive compilation of observational datasets including the profiles gathered by instrumented marine mammals. The mapping method consists first of a decomposition in vertical modes of the combined temperature and salinity profiles. Then the resulting principal components are optimally interpolated on a regular grid and the monthly climatological profiles are reconstructed, providing a physically plausible representation of the ocean. The ASF is located with a contour method and a gradient method applied on the temperature field, two complementary approaches that provide a complete view of the ASF structure. The front extends from the Amundsen Sea to the eastern Weddell Sea and closely tracks the continental shelf break. It is associated with a sharp temperature gradient that is stronger in Winter and weaker in Summer. The emergence of the front in the Amundsen and Bellingshausen sector appears seasonally variable (slightly more westward in Winter than in Summer). The investigation of the density gradients across the shelf break indicates a Winter slowdown of the baroclinic component of the Antarctic Slope Current at the near-surface, in contrast with the seasonal variability of the temperature gradient.

Corresponding author: Etienne Pauthenet, etienne.pauthenet@locean-ipsl.upmc.fr

Abstract

The Antarctic Slope Front (ASF) is a fundamental feature of the subpolar Southern Ocean that is still poorly observed. In this study we build a statistical climatology of the temperature and salinity fields of the upper 380 m of the Antarctic margin. We use a comprehensive compilation of observational datasets including the profiles gathered by instrumented marine mammals. The mapping method consists first of a decomposition in vertical modes of the combined temperature and salinity profiles. Then the resulting principal components are optimally interpolated on a regular grid and the monthly climatological profiles are reconstructed, providing a physically plausible representation of the ocean. The ASF is located with a contour method and a gradient method applied on the temperature field, two complementary approaches that provide a complete view of the ASF structure. The front extends from the Amundsen Sea to the eastern Weddell Sea and closely tracks the continental shelf break. It is associated with a sharp temperature gradient that is stronger in Winter and weaker in Summer. The emergence of the front in the Amundsen and Bellingshausen sector appears seasonally variable (slightly more westward in Winter than in Summer). The investigation of the density gradients across the shelf break indicates a Winter slowdown of the baroclinic component of the Antarctic Slope Current at the near-surface, in contrast with the seasonal variability of the temperature gradient.

Corresponding author: Etienne Pauthenet, etienne.pauthenet@locean-ipsl.upmc.fr
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