Physical Oceanography (Feb 2023)
Features of Seasonal Variability of Chlorophyll a Concentration in Different Regions of the Southern Atlantic Based on Satellite Data
Abstract
Purpose. Based on the long-term satellite optical measurements, the work is to study seasonal variability of the chlorophyll a concentration on the sea surface in different regions of the Southern Atlantic, determine its spatial features, identify the areas where the values of the chlorophyll a concentration are maximum, and to analyze the reasons for its increase in these regions. Methods and Results. The data on the chlorophyll a concentration obtained from the MODIS-Aqua measurements for 2002–2019 in the region 30°–80°S, 70°W – 25°E were used. Spatial variability of the surface chlorophyll a concentration, its seasonal dynamics and the time of the seasonal peak occurrence were studied. Four zones of local maxima of the chlorophyll a concentration were identified (the Argentinean shelf, the islands of South Georgia, the area of water removal from the Antarctic Peninsula and the Antarctic shelf east of the Weddell Sea); for each of them the features of seasonal variability were analyzed in details. Conclusions. In agreement with the previous papers, the peak chlorophyll a concentration and the beginning of bloom in the regions under study are observed later than in the high latitudes: in the northern part – in November – December, and in the southern one – in January – February. The exception consists in the quite extensive areas to the east of the nutrients powerful sources (islands, shelf waters), where the time of occurrence of the chlorophyll a concentration peak values is related to the advection impact, that results in its arising with a delay which is required for transferring the nutrients by the currents. The basic factors promoting appearance of the areas with the increased chlorophyll a concentrations are the interaction between the topography features and the Antarctic Circumpolar Current fronts, and ice melting in the marginal zone.
