The effect of freshwater discharge from the Godavari river on the occurrence of local upwelling off the east coast of India

Abstract

A numerical model is described and applied to investigate the combination of the wind- and estuarially-driven circulation of water off the east coast of India. A previous numerical modelling study has shown that the estuarial discharge from the Hugli and Mahanadi Rivers may, consistently with an interpretation of observational data, inhibit the occurrence of coastal upwelling as far south as Visakhapatnam. Further south of this location, there is a substantial discharge of freshwater during the monsoon season into the Bay of Bengal from the Godavari River that might possibly have a similar suppressive effect on the coastal upwelling dynamics. In a process-orientated evaluation, it is shown that a representative rate of discharge from the Godavari River leads to a marked cross-shelf spread of a plume of relatively low-salinity water and that the associated dynamical structure is then correspondingly modified so as to weaken the local coastal upwelling tendencies in the surface layers of the ocean that would exist in the sole presence of south-westerly wind-stress forcing and the northern estuarial outflow.