Vertical structure of mesoscale eddies and their impact on the modulation of tracer fields in the eastern Arabian Sea
Abstract
The present study utilises a combination of observation and ocean reanalysis data to comprehend the vertical structure of mesoscale eddies and their influence on the modulation of tracer properties (temperature, salinity, and chlorophyll) in the Eastern Arabian Sea (EAS). Mesoscale eddies in the EAS are surface intensified, with the geostrophic anomaly concentrated in the upper 100 m and with a surface thermohaline anomaly core in general. However, significant spatial variation in the composite eddy structure is observed within the study region, with the eddy core being shallower in the south than in the northern parts of the EAS. The temperature anomalies induced by eddies are found to be weak and shallow in summer compared to spring/winter. The salinity structure also exhibits a strong seasonality, with the strong surface salinity core changing to a diffused one from spring to summer. Mesoscale eddies play a significant role in modulating the vertical distribution of temperature, salinity and chlorophyll in the EAS. The depth of subsurface salinity and chlorophyll maximum is deeper (shallower) in the presence of anticyclonic (cyclonic) eddies. Eddies contribute about 30% (26%) of the intraseasonal salinity (temperature) variability in the upper 200 m in the EAS. This study also highlights that mesoscale eddies play an important role in redistributing the warm and low-saline water carried by the West India Coastal Current into the deeper areas of EAS, and this leads to horizontal inhomogeneity of thermohaline properties in the region, particularly in winter and spring.
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