Atmospheric Interactions and Marine Productivity: Assessing Chlorophyll-a Responses to Dust, AOD, and Humidity in the Arabian Sea

Marine chlorophyll-a plays a crucial role in marine ecosystems worldwide and is essential for photosynthesis in certain plankton and aquatic plants. The Arabian Sea is vital for biodiversity and climate regulation. Hence, remote sensing techniques are employed to monitor chlorophyll-a and understand the spatiotemporal fluctuations of phytoplankton and biomass in these waters. This research investigates the spatiotemporal trends of relative humidity acquired from AIRS, MERRA-2 model’s dust column density, and MODIS retrieved Aerosol Optical Depth (AOD) and Chl-a across the Arabian Sea (4ᵒN-26ᵒ N to 50ᵒE-78ᵒE) spanning from 2003 to 2023. Cross-wavelet analysis and correlation of Chl-a with relative humidity, dust, and AOD over the AS are also analyzed in this research. An anti-phase and phase lag state has been found between Chl-a and these variables, showing a negative correlation. Correlation maps reveal that Chl-a in the Arabian Sea has a negative correlation with dust (-0.6 to -0.1) across most areas, suggesting that dust deposition may inhibit phytoplankton growth due to reduced light penetration or other factors. Similarly, the negative correlation with relative humidity (-0.9 to -0.1) could reflect adverse climatic conditions during humid periods. In contrast, the positive correlation with AOD (0.1 to 0.9) in the southern region implies that aerosols might enhance phytoplankton productivity through nutrient deposition, while negative values in the northern region (-0.9 to -0.4) highlight contrasting dynamics. While dust column mass density and Chl-a show decreasing trends, aerosol optical depth and relative humidity are increasing. Moreover, the highest variability of Chl-a has been observed in DJF close to the shores of Oman, Iran, and Pakistan.