The distribution of water masses in the South Shetland Islands area during FIBEX

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Observations on stratification of temperature, salinity and sound-velocity in the Weddell-Scotia Confluence area were made during the international FIBEX (First International BIOMASS Experiment) multiship echo survey between January 26 and March 1,1981. The measurements, performed from R. V. WALTHER HERWIG, during the second cruise leg between March 10 and 22,1981 were done in the area of the South Shetland Islands. By means of a water mass-analysis and geostrophic computations the areas of specific interest to krill biology are related to the sphere of influence of the Bellingshausen Sea, the Scotia Sea and the Weddell Sea, respectively. The temperature measurements during the FIBEX echo survey indicate the complex structure of the Weddell-Scotia Confluence. The interaction of waters from the Scotia Sea and the Weddell Sea leads to a meandering frontal zone. From this meandering current border a patch of "warm" Scotia water was observed to travel into the Weddell Sea. The striking coincidence in the geographical location of a meander east of 50°W with previous observations might be a reference that the bottom topography of the southern Scotia Ridge plays an important role in the formation and maintenance of the Weddell-Scotia Confluence properties. A detailed water mass analysis reveals that the Weddell Sea water effectively influences the Bransfield Strait and the Gerlache Strait. Geostrophic computations corroborate these findings.