Estimation of Salt and Fresh Water Transports in the Bay of Bengal

The importance of Indian Ocean circulation dynamics to regional and global weather is increasingly recognized due to improved ocean observations in the last few decades. Observational and modeling efforts are directed towards understanding the impact of intraseasonal variability and interannual variability on monsoon variability. A key component to better understanding these interactions is understanding salt transport within a dynamic freshwater flux environment. Freshwater influx leads to intense salinity stratification in the Bay of Bengal (BoB) and helps to maintain a warmer surface temperature. The specific objectives of this study are as follows: (1) to estimate the inter-basin exchange of salt in the tropical Indian Ocean and to delineate pathways of high/low salinity water masses, and (2) to study the role of salinity on barrier layer dynamics in the Bay of Bengal. We used the global HYbrid Coordinate Ocean Model (HYCOM) with a horizontal resolution of 1/12 degrees and 32 hybrid layers in the vertical. The hybrid coordinate system is isopycnal in the open, stratified ocean, but smoothly reverts to a terrain-following coordinate in shallow coastal regions, and to a pressure coordinate in the mixed layer and/or unstratified seas. This is an advantage because no single coordinate system is optimal everywhere. A fine resolution global model is needed for this work because of the global nature of the problem we plan to study, and because recent research has shown the importance of high horizontal resolution for the accurate representation of many key features of the Indian Ocean, features which can and do impact ocean salinity. The model is configured on a Mercator grid from 78 degrees S to 47 degrees N, with a bipolar grid used north of 47 degrees N. Daily global HYCOM simulations were used to estimate salt and fresh water transports in the Indian Ocean.