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The Weddell-Scotia Confluence

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  • 1 Department Of Oceanography, Texas A&M University, College Station 77843
  • | 2 Instituto Hidrografico the la Armada, Valparaiso, Chile
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Abstract

The Weddell-Scotia Confluence is the zone separating the waters of the Weddell Sea from those of the Scotia Sea. Available historical hydrographic station data were examined to improve the description of this boundary zone from its western limit near the northern tip of the Antarctic Peninsula (∼55°W) to 20°W. Vertical sections of potential temperature, salinity, oxygen and density, as well as horizontal property distributions, confirm that the waters in the western part of the Weddell-Scotia Confluence are more homogeneous in the vertical than the surrounding waters and that, at depth, this zone is characterized by relatively low temperatures and salinities and high oxygen values. Near the sea surface, on the other hand, the confluence is characterized by relatively high salinities and low oxygen values. The distinguishing characteristics attenuate toward the east. Previous speculation has been that the relative homogeneity of this zone is due to vertical convection driven during winter by ice formation and air/sea interaction. Here we propose that the unusual properties of this zone may be due instead to vertical mixing processes occurring within the oceanic lateral boundary layer which, while acting to homogenize the water column, incorporate into the water column cold, fresh meltwater from the ice (principally that of continental origin) which is nearly always present in this area. The influence of such a process would not be restricted to the winter season.

Abstract

The Weddell-Scotia Confluence is the zone separating the waters of the Weddell Sea from those of the Scotia Sea. Available historical hydrographic station data were examined to improve the description of this boundary zone from its western limit near the northern tip of the Antarctic Peninsula (∼55°W) to 20°W. Vertical sections of potential temperature, salinity, oxygen and density, as well as horizontal property distributions, confirm that the waters in the western part of the Weddell-Scotia Confluence are more homogeneous in the vertical than the surrounding waters and that, at depth, this zone is characterized by relatively low temperatures and salinities and high oxygen values. Near the sea surface, on the other hand, the confluence is characterized by relatively high salinities and low oxygen values. The distinguishing characteristics attenuate toward the east. Previous speculation has been that the relative homogeneity of this zone is due to vertical convection driven during winter by ice formation and air/sea interaction. Here we propose that the unusual properties of this zone may be due instead to vertical mixing processes occurring within the oceanic lateral boundary layer which, while acting to homogenize the water column, incorporate into the water column cold, fresh meltwater from the ice (principally that of continental origin) which is nearly always present in this area. The influence of such a process would not be restricted to the winter season.

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