ENSO와 남극해 북서대서양해역의 엽록소 변동

Abstract

11-year (1997-2008) weekly and monthly time-series of satellite ocean color data have been examined to understand the dominant temporal and spatial patterns of chlorophyll-a in the southwest Atlantic sector of the Southern Ocean (SASSO). Using empirical orthogonal function analysis and K-means classification, we classified the study area into 8 regions, which is in good accordance with the oceanographic and topographic features. Examination of the time-series of chlorophyll-a in each region revealed that contrary to our expectation, regular seasonal phytoplankton blooms were observed only in a limited area. Interannual variability of the surface chlorophyll in some regions revealed longer periodicity (~6 years). The periodicity seemed to relate to ENSO and is thought to be related to sea ice dynamics influenced by the Antarctic Circumpolar Current. More recently, the high-latitude atmospheric ENSO response appeared to have intensified. Since the second component of EOFs was interpreted to be related to blooms associated with ice-retreat, we checked the relationship between PC2, and the SOI (Southern Oscillation Index) and SAM (Southern Annular Mode). PC2 shows a similar trend with the SOI until 05/06. Spearman correlation coefficient for the period up to 05/06 was significant at probability of 5% (p=0.013). However, the correlation coefficient between PC2 and the SAM for the same period was not significant. After 05/06, PC2 behaved differently from the SOI or SAM. PC2 was dominant in sDP, wSC, and eSC region implying that ENSO signals primarily propagate east through the ACC and may affect sea-ice dynamics particularly in the south of PF. However, the change after 05/06 is not clear.