Physical oceanographic setting of the Siedlecki January 1987, South Shetland Island data set
In the vicinity of the northern tip of the Antarctic Peninsula, the Bransfield Straits and South Shetland Islands, cold polar waters from the Weddell Sea meet warmer circumpolar water from the Pacific Ocean. A series of fronts form which are collectively referred to as the Weddell-Scotia Confluence. Within the Confluence region the Weddell Gyre water is separated from the Pacific or Scotia Sea water by a zone of varied width (10 to 100 km) of water which can best be considered as continental margin water, advected into the region along the extreme western edge of the Weddell Gyre. It is relatively cold and low in salinity throughout the water column and prone to deep reach convective events, even as far north as the Bransfield Straits. Along the northern boundary of the Weddell-Scotia Confluence (the Scotia Front), where the Pacific water is encountered, there are indications of vigorous mixing processes of Bransfield Straits water (derived from the Weddell, with further local modification): an intrusive layer of Pacific derived relatively warm-salty water near 300 meters depth and deeper intrusions (500-1 500 meters; e.g. Siedlecki stations 217, 226, 231, 235, 236 and 250) of Pacific water, as the Scotia Front protrudes to the south, perhaps associated with mesoscale structures.
The Weddell-Scotia Confluence in the Bransfield Straits is associated with abundant krill populations. It is speculated that mixing of Weddell and Pacific waters near the tip of the Antarctic Peninsula is an important environmental feature related to this abundance.