A Model for the Vertical Chlorophyll-a Distribution in the Bay of Bengal Using Remote Sensing Data

Deep chlorophyll maxima (DCM) layer is the concentrated patch of phytoplankton, which occurs as a layer at a depth extending few meters vertically and spanning many kilometers horizontally. These highly productive regions of the ocean are signatures of critical physical, chemical, and biological processes in the aquatic environment. This study reports and characterizes a DCM layer observed in the Bay of Bengal during three different cruises conducted in 2015, 2016, and 2018. The relationships of the defining parameters for the DCM like the depth and maximum chlorophyll concentration are modeled with respect to the biogeochemical parameters and are validated for the region. A new approach using the density for the estimation of the vertical chlorophyll profile was formulated. The DCM characteristics and covariation with respect to the other parameters are, thus, formulated and the factors controlling the DCM in this region are characterized. The model was applied to satellite remote sensing data to derive the vertical profiles of chlorophyll layer in the Bay of Bengal waters. The results were discussed in the context of understanding of the underlying biological and physical processes as well as subsurface phytoplankton biomass and the carbon cycle in the region.