Seasonality of the vertical distribution of chlorophyll-a in the sublatitudinal zones of the Antarctic part of the Atlantic according to direct and remote sensing data

The article discusses the results of the analysis of 469 chlorophyll a profiles obtained from the buoys of the project Biogeochemical-Argo from May 7, 2015 to May 14, 2018 in the Drake Passage and the open part of the Scotia Sea between 53–65° S, 40–70° W. Profiles led to standard horizons. It was noted that during the period under review it became possible to trace the dynamics of seasonal changes in the concentration of chlorophyll-a in four sublatitudinal zones. In the area under consideration, phytoplankton reached its highest development in December, in the SFZ (Secondary frontal zone) the maximum values reached 4.11 mg / m3, the lowest concentration of chlorophyll-а was observed in August, while the lowest values of the maximum were also observed in the SFZ and were 0.16 mg/m3. According to the dynamics of the variability of the curves of chlorophyll values, the similarity between the SASM (sub-antarctic surface water mass) and SPFZ (South polar frontal zone) zones and between AZ (Antarctic zone) and SFZ is highlighted. In the areas of SASM and SPFZ, the range of values of the chlorophyll-а maximum during the year was less (0.22–3.45 mg/m3) than in the southern regions, the second peak was in May. AZ and SFZ had similar pronounced seasonal differences, the values of chlorophyll content in the maximum zone ranged from 0.09–8.02 mg/m3, the second peak was observed in February. Surface maxima were observed in 33.9% of cases, mainly in the winter period in the area of the SASM. The difference between the surface values and the values in the layer of the maximum in the winter period for all zones was 5–12%, in the summer period in the SASM and AZ reached 48%. As a trend, an increase in the average maximum depth from February (37 m) to October (15.5 m) was observed.