A summer monsoon pump to keep the Bay of Bengal salty

P. N. Vinayachandran1 , D. Shankar2 , S. Vernekar2 , K. K. Sandeep1 , P. Amol2, C. P. Neema1 , and A. Chatterjee2

1Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore 560012, India

2 CSIR - National Institute of Oceanography, Dona Paula, Goa 403004, India.

The Bay of Bengal receives a large influx of freshwater from precipitation and river discharge. To maintain the seasonal sea level as well as the the salt balance of the bay, this excess freshwater has to exported out of the bay. This export is accomplished by the East India Coastal Current (EICC) and the Winter Monsoon Current (WMC), which flows into the eastern Arabian Sea, and by an equatorward flow along the eastern boundary. The water that leaves the bay carries certain amount of salt with it and the required inflow of saltier water, in order to maintain the salt balance of the bay, occurs via the Summer Monsoon Current (SMC), which flows from the Arabian Sea into the Bay of Bengal. This saltier water, however, slides under the lighter surface water of the bay. Maintaining the salt balance of the bay therefore demands upward mixing of this saltier, subsurface water. We have shown that an efficient mechanism for this mixing is provided by upward pumping of saltier water in several bursts during the summer monsoon along the meandering path of the SMC. Advection by currents can then take this saltier water into the rest of the basin, allowing the bay to stay salty despite a large net freshwater input. This discovery was made during a field experiment during July -August, 2009 into the southern Bay of Bengal on board ORV Sagar Nidhi as a part of the Continental Tropical Convegence Zone (CTCZ) programme.

For details:

P. N. Vinayachandran , D. Shankar , S. Vernekar , K. K. Sandeep, P. Amol, C. P. Neema, and A. Chatterjee, (2013), A summer monsoon pump to keep the Bay of Bengal salty, Geophysical Research Letters, DOI: 10.1002/grl.50274,