Spatiotemporal Variability of Chlorophyll a in the Atlantic and Indian Sectors of the Southern Ocean during February-April of 2000 According to Satellite and Expeditionary Data

In February and April 2000, in the Southern Ocean between Africa and Antarctica, the concentration of chlorophyll ( C sub(chs)) in the surface layer was not high (0.1-0.3 mg/m super(3)). The zones of increased C sub(chs) values (0.6-2.0 and over 2.0 mg/m super(3)) were located between the Southern Subtropical and Subantarctic fronts, near the Polar front, and to the south of the Antarctic Divergence. From February to April, in the open areas of the Southern Ocean, a general C sub(chs) decrease was observed. A similar trend was also noted in the near-shore seas of the East Antarctic. At the shelf of the Sea of Cosmonauts, within the upper mixed layer, the content of chlorophyll amounted to 0.34-0.37 mg/m super(3). In the area of the continental slope, we registered the formation of a subsurface chlorophyll maximum (0.52- 0.56 mg/m super(3)) at a 20-m depth, which deepened to 70 m when passing to the deepwater area. The positive correlation with a high coefficient ( r = 0.939) between the field and satellite data ( C sub(chs) and C sub(sat), respectively) allows one to conclude about the applicability of the SeaWiFS algorithm for the estimation of the chlorophyll content within the surface layer in the Antarctic areas studied. In the course of the ice formation in Prydz Bay, during five days, the content of chlorophyll in different phases of the new ice increased by a factor of 2.9, whereas the values of this parameter in the surrounding waters remained quite invariable. The C sub(sat) values were 6.3 times as high as those obtained experimentally for the sludge ice. Because of the large areas occupied by floating ice, the sole usage of satellite data may cause great errors in the productivity estimation of the East Antarctic seas.