Spatial and temporal scales of variability in the Meghna estuary from ocean remote sensing

Abstract

Meghna Estuary is a very complex and dynamic estuarine system because of its irregular shape, wide seasonal variation and the changing role of tides. Every year, a major portion of the flow laden with high amount of sediments from the Ganges-Brahmaputra-Meghna river system are transferred through this estuary to the Bay of Bengal (BoB). The purpose of this analysis is to extract the dominant patterns of satellite Chlorophyll-a (CHL), Total Suspended Matter (TSM) and Sea Surface Temperature (SST) variability off the Meghna Estuary. CHL and TSM data were downloaded from GlobColour Project (http://globcolour.info/) and SST data were downloaded from Ocean Colour Project (https://oceancolor.gsfc.nasa.gov) using the monthly, 4km resolution of the global earth domain over eleven years (April 2002-April 2012). A temporal Empirical Orthogonal Function (EOF) analysis was performed to all the variables. The results revealed that the mean spatial distribution of the selected environmental variables in the Meghna estuary and its adjacent area during the study period showed clear latitudinal patterns in case of CHL and TSM, with higher values around the northern coast and a gradual offshore decreasing gradient. The SST map showed the same spatial pattern but with lower temperature values around the northern coastal fringe and higher values offshore. Only the first EOFs mode was found to be relevant, representing 25.55%, 15% and 89.43% of the CHL, TSM and SST variance, respectively, and depicted that the seasonal variability is the dominant pattern in this complex estuarine environment.