How do Bay of Bengal surface currents change with the monsoon seasons?

Surface currents in the Bay of Bengal are primarily driven by the seasonal monsoon winds, which cause the water's circulation pattern to reverse throughout the year.12

• Northeast Monsoon (November–March): During this season, the prevailing winds produce a clockwise circulation of surface waters within the bay.2
• Southwest Monsoon (April–October): As the southwest monsoon sets in, the wind direction reverses, driving a counterclockwise circulation of the bay's surface waters.12

These shifts are part of the broader Monsoon Current system of the northern Indian Ocean, which distinguishes the region from the Atlantic and Pacific oceans where currents remain more stable. Additionally, the bay experiences weak upwelling in the northeast during the northeast monsoon, and its physical properties—such as surface salinity and density—fluctuate significantly due to these seasonal changes and high river discharge.12