Mesoscale Variability of the Ocean in the Northern Part of the Weddell Sea

Abstract—Results of a mesoscale survey in the Powell Basin in the northern part of the Weddell Sea are analyzed. The survey included 24 CTD casts (6 × 4) with an interval of six nautical miles. Measurements of water transparency, fluorescence, and plankton catches using the Bongo and Jedy nets were performed. The survey covered a region of an oceanographic front. The front is manifested by sharp horizontal gradients of temperature and chemical properties. The front exists due to the differences in the water properties typical for the entire Weddell Sea and water from the western part of the sea, which is formed in a shallow region covered with ice and icebergs that prevent warming of the upper layer of water by the solar irradiance. The front in the region of the mesoscale survey appears due to the separation of meanders from the large-scale front in the northern part of the Weddell Sea and displacement of the ring with cold water from the bottom elevation to the region of the survey. The differences in the water structures north and south of the front are also pronounced in chemical properties, optical characteristics of the upper layer, and different concentrations and species of phytoplankton, zooplankton, and pelagic fish.