Two-decadal variation of satellite-derived chlorophyll-a concentration and sea surface temperature in the Arabian Sea and Bay of Bengal

This study presents a comprehensive satellite-based quantitative analysis spanning two decades (2002–2022) to examine daily, monthly, and annual chlorophyll concentrations (Chl-a), sea surface temperature (SST), and primary productivity (PP eu ) in the Arabian Sea (AS) and the Bay of Bengal (BoB). Utilizing MODIS-Aqua satellite data and applying standard ocean colour algorithms, we generated Chl-a, SST, and PP eu products at the scale of 1 km resolution for in-depth analyses, including long-term trends, temporal patterns, and productivity comparisons. Notable findings include elevated Chl-a concentrations in the AS during February–March and in the BoB during August–September. Chl-a in the AS peaked at 5.57 times higher than in the BoB, with primary productivity estimates ranging from 196.48 to 242.65 gC m –2 year –1 in the AS, compared to 144.15 to 172.06 gC m –2 year –1 in the BoB. This suggests that the AS fixes carbon at approximately 1.34 times the rate of the BoB, indicating its higher capacity for carbon fixation. The study highlights the AS’s heightened sensitivity to climatic variations compared to the BoB, emphasizing the importance of regional climatic impacts on marine productivity. Research highlights Comprehensive satellite-based analysis of temporal trends in chlorophyll concentrations, sea surface temperature, and primary productivity in the Arabian Sea and the Bay of Bengal over two decades. Investigation of satellite-derived ratios to study elevated chlorophyll concentrations in both seas. Arabian Sea’s Chl-a peaked at 5.57 times that of the Bay of Bengal. Arabian Sea fixes carbon at approximately 1.34 times the rate of the Bay of Bengal. Insights into long-term stability and evolving dynamics of the Arabian Sea and the Bay of Bengal. Potential trajectories of chlorophyll concentrations, sea surface temperature, and primary productivity in the coming years based on 20 years of satellite data.