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Studying sub-mesoscale ocean dynamics in the Bay of Bengal and its role in ocean biology using SWOT and EOS-06/OCM-3 observations
Principle Investigator: Neeraj Agarwal (Space Applications Center, ISRO)
Co-Investigator(s): Aditya Chaudhary, Smitha Ratheesh
The Surface Water Ocean Topography (SWOT) mission is a groundbreaking endeavor that uses cutting-edge technology to provide high-resolution, synoptic observations of ocean dynamics and inland water bodies. For the first time, SWOT offers a two-dimensional view of sea level, capturing detailed data over large areas in a single pass. This high-resolution swath product has immense potential to improve our understanding of oceanic processes, particularly in regions like the Bay of Bengal (BOB), which is known for its complex dynamics.
The Bay of Bengal exhibits intricate oceanographic features, such as mesoscale eddies and strong freshwater-induced stratification due to significant river discharge and precipitation. These factors play an essential role in stabilizing the upper ocean and sustaining the oligotrophic nature of surface waters in the region. Mesoscale eddies are pivotal in influencing the region's ocean circulation patterns and marine ecosystem. Cyclonic eddies, in particular, promote biological activity by inducing upwelling and enhanced nutrient mixing, leading to increased phytoplankton growth. Consequently, mesoscale eddies are important inputs for mapping Potential Fishery Zones (PFZs), as they directly impact primary productivity and marine ecosystems.
Despite the understanding of mesoscale eddies and their role in chlorophyll variability, challenges remain in studying sub-mesoscale processes, which require higher-resolution sea level observations. SWOT’s high-resolution sea level data, coupled with ocean color data from EOS06/OCM3, presents a unique opportunity to explore the Bay of Bengal’s dynamics in greater detail. This combined dataset offers insights into ocean current behavior, eddy structures, and their influence on chlorophyll distribution through horizontal stirring processes.
The integration of SWOT data with other satellite observations, such as scatterometer winds, can provide a better understanding of ocean surface currents at sub-mesoscale levels. These surface currents also have implications for subsurface ocean dynamics, making high-resolution ocean model simulations essential. SWOT’s swath sea level data offers a new frontier for ocean data assimilation, allowing for improved representation of fine-scale current structures in ocean circulation models—one of the key challenges in ocean modeling. Previous studies have demonstrated that assimilating satellite-derived sea level data into models enhances the simulation of sea level, ocean currents, and thermal structures, which are crucial for understanding the coupled physical and biogeochemical processes that govern marine ecosystems.
To deepen the study of ocean dynamics and phytoplankton variability in the Bay of Bengal, two experimental objectives are proposed. The first is to examine the co-variability between ocean surface currents and chlorophyll using SWOT, OCM3, and scatterometer data. The second is to identify the role of horizontal stirring in chlorophyll distribution and compare the results with low-resolution satellite current analyses. Additionally, the study aims to assess the impact of assimilating SWOT-derived sea level anomalies (SLA) into coupled biogeophysical models to improve simulations of small-scale physical and biological features. To validate these simulations, data from various satellites, such as winds, sea surface temperature, and chlorophyll, as well as in situ platforms like Argo floats and buoy networks, will be used.