Bio-physical Changes in the Eastern Arabian Sea due to Ocean-Atmospheric Teleconnections

Abstract

Arabian Sea is in general biologically most productive region in the North Indian Ocean, in particular eastern Arabian Sea. However, there is a lack of pre-existing studies performed to reveal the seasonal and interannual variability of the primary production. The potential role of atmospheric and oceanographic events on promoting the distinct development of phytoplankton in the northern and southern parts of eastern Arabian Sea regions was investigated in this article. In order to study the temporal variability of the bio-physical parameters, we used 12 years (1998-2009) of Sea WiFS chlorophyll-a data and 10 years (2000-2009) of QuickSCAT wind stress data (zonal and meridional) as two important forcing parameters. Relative impacts of the Indian Ocean Dipole (IOD), associated with the global climatic event of El Nino Southern Oscillation (ENSO) on biophysical parameters of eastern Arabian Sea during the study period have been analyzed at the two regions. Seasonal and interannual variabilities are clearly observed in both chlorophyll-a and wind stress time series. The overall seasonal variation for chlorophyll-a were 0.17 and 2.29 mg m-3 with a standard deviation of 0.03 and 0.54 mg m-3 for the northern and southern regions, respectively, and the coefficient of variation was 8-65%. The relationship between chlorophyll-a and multivariate ENSO index was negative at northern and southern regions in all seasons, and the IOD also showed negative relation except pre monsoon sea.