Science Meetings

Basin-Scale Exchange of Salt and Fresh Water Between the Araban Sea and the Bay of Bengal During Monsoons
D'Addezio, J., Subrahmanyam, B., Nyadjro, E., and Murty, V. (11-Nov-14)

The Northern Indian Ocean (NIO) presents a unique dipolar sea surface salinity (SSS) structure with the salty Arabian Sea (AS) on the west and the fresher Bay of Bengal (BoB) on the east. At the surface, the largest driver of seasonal salinity variability is the monsoonal riverine runoff and winds and their ability to transport volume between the two basins. Aquarius and Argo capture SSS anomalies during each monsoon and provide an observational baseline to assess model performance for a number of different calculations. Using Argo, various reanalyses, and model simulations over the 4 year period from January 2008 to December 2011, the upper 200 m layer salinity structure of this contrasting, yet interconnected, region is quantified. Salt and freshwater fluxes show a strong semi-annual zonal variation between the two basins along (or south of) Sri Lanka twice a year. Regional salt budgets reveal the seasonality of each advection term. The BoB shows the largest seasonal variability in salinity with changes up to ~0.5 psu month-1 during the northeast and southwest monsoons. Meridional depth-integrated salt, freshwater, and volume transports along a slice of each basin at 6°N reveal the advective processes at depths greater than the mixed layer. In the AS, maximum volume transport of ~3 Sv (1 Sv = 106 m3 s-1) occurs towards the north in July when the Somalia current is at its peak. In the BoB, southward volume transport of ~3 Sv occurs during the same period. Neither the southwest nor northeast monsoon currents dominate the transport profile of either basin at this latitudinal cross-section.