Dynamics of subsurface chlorophyll maxima in the northern Indian Ocean

Subsurface chlorophyll maxima (SCM) significantly contributes to oceanic primary productivity, emphasizing the need to study its dynamics and governing mechanisms. We used datasets from various platforms to investigate relationships between the SCM characteristics (SCM depth (Z_SCM), SCM magnitude (Chl_max), SCM thickness (T_SCM)) and environmental variables modulated by various physical processes in the Northern Indian Ocean (NIO). In the Arabian Sea (western NIO), seasonal processes like convective mixing and upwelling, primarily regulated the SCM characteristics. In the Bay of Bengal (eastern NIO), SCM characteristics were jointly influenced by fresh water influx, barrier layer formation, presence of eddies, and the propagation of Kelvin and Rossby waves. Any changes in these oceanic processes, potentially driven by climate change, could therefore impact oceanic primary production. Additionally, a positive association obtained between Chl_max and downward CO₂ flux, while a shallower Z_SCM, associated with higher concentrations of DMS, indicated SCM's role in regulating atmospheric gases.