<p>An accurate representation of mixed layer salinity (MLS) in the numerical models is essential for better simulation of near-surface temperature and biogeochemical state in the Bay of Bengal (BoB). Between February and December 2015, three moorings were deployed in an approximate triangle configuration in the northern BoB (nBOB) around 18^°N, 89.5^°E, with an approximate spatial separation of 30&#xa0;km. The zonal and meridional sea surface salinity (SSS) gradients derived from the triangularly configured mooring array, along with near-surface meteorological and sub-surface measurements, provided an opportunity for the reliable estimation of all the major components of the MLS budget. Observation exhibits prominent sub-seasonal variability in the SSS comprising seven distinct freshening and salinification events with a range of 1.5 to 7 psu between August and December 2015. Conversely, such high-frequency variability in SSS was roughly absent during the first half of the study period between February to July 2015. The MLS budget analysis shows that horizontal advection and vertical processes dominate the MLS variability in the nBoB during the period of prominent sub-seasonal variability, while the local freshwater flux contribution is significant during the occasional intense rainfall events. Our analysis further suggests that enhancement of the lateral salinity gradient was the primary factor for the prominent sub-seasonal variability in the horizontal advection processes during the latter half of 2015. It is also found that the spread of riverine discharge water into the study area by horizontal advection and stirring of this freshwater with pre-existing high-salinity water by mesoscale eddies generates large SSS gradients.</p>