Impacts of the Red Sea and Persian Gulf on the Northern Indian Ocean in Numerical Simulations

Warm saline water masses emanating from the Persian Gulf (PG) and the Red Sea (RS) spread across a large area of the northern Indian Ocean upper layers, affecting the thermocline stratification, the circulation, and the air-sea exchanges over the Arabian Sea (AS) and Bay of Bengal (BoB). To explore the significance of these waters, we use numerical simulations to investigate the impact of isolating (closing) the RS and PG. The results show that the differences between the model runs, with and without the RS and PG, have marked effects on the AS and BoB seasonal variability. As expected, the major differences are concentrated in the surface mixed layer and thermocline of the AS. However, differences are also found further east in the BoB, mainly during the boreal summer. Significant differences are present in the air-sea freshwater and heat fluxes calculated by the model. In addition to the seasonality, there are significant interannual variability, with possible correlation with the El Nino-Southern Oscillation. Results of the experiments suggest that the upwelling in the Sri Lanka Dome, in the southwestern Bay of Bengal, would have responded differently to the 2009-2010 El Nino-La Nina in the absence of PG and RS input.

Automated summary

Warm saline water masses from the Persian Gulf and the Red Sea have a significant impact on the upper layers of the northern Indian Ocean, affecting thermocline stratification, circulation, and air-sea exchanges. By simulating the closure of the Red Sea and Persian Gulf, it is found that there are marked differences in the seasonal variability and air-sea fluxes in the Arabian Sea and Bay of Bengal. The experiments suggest that the upwelling in the southwestern Bay of Bengal would have responded differently to the El Nino-La Nina event in the absence of the Persian Gulf and Red Sea input.