1997년-2008년 시기 남대서양해역 엽록소 변동의 계절 및 경년변화 연구

Abstract

11-year (1997–2008) weekly and monthly time series of satellite-observed ocean color data was examined to understand the dominant temporal and spatial patterns of chlorophyll-a in the southwest Atlantic sector of the Southern Ocean. From the 11-year monthly time series of SeaWiFS/MODIS chlorophyll-a data and k-means classification, the study area was classified into eight regions, which were in good accordance with the oceanographic and topographic features. Examination of the chlorophyll-a time series in each region unexpectedly revealed that regular seasonal phytoplankton blooms were observed only in a limited region of the study area. Of the eight regions, only two regions showed typical seasonal blooms, and one region showed weak seasonality, whereas other regions exhibited irregular seasonal blooms of variable duration. The absence of regularity in seasonal blooms is attributed to relatively shallow winter mixing, which would prevent entrainment of limiting micronutrients such as iron. The higher chlorophyll-a concentrations corresponded with topographic features of the study area. In the South Georgia region, chlorophyll-a showed a significantly correlation with geostrophic current velocity, suggesting that topographic effects depend on the interaction of current strength and topographic structure. Interannual variability of the surface chlorophyll-a in some regions revealed longer periodicity (~6 years). The periodicity seemed to be related to El Niño–Southern Oscillation and to sea ice dynamics influenced by the Antarctic Circumpolar Current. In the study area, topographic effects and sea ice seem to be the most important factors controlling phytoplankton blooms. Possible implications of seasonality and limiting factors of phytoplankton in the SASSO are discussed.