Vivek Shilimkar

State of the ocean is determine by two important parameters – temperature and salinity. The most noticeable result of climate change is the rise in atmospheric and sea surface temperature (SST). Anomalous increase in SST can change the ocean dynamics and thermodynamics, and the ocean-atmosphere interaction. Another parameter that determines the state of the ocean is salinity. Salinity plays an important role in mixing, barrier layer formation, Thermohaline circulation etc. Along with these salinity plays a direct role in evaporation. Hence understanding the variability of salinity is important, so as to improve the knowledge of role of salinity in climate system.

Our study examines the variability and trend in tropical Indian Ocean sea surface salinity in changing climate using an observed data and CMIP5 historical simulations. The results indicates the dipole like variation in sea surface salinity (SSS) associated with the precipitation during Indian Ocean Dipole and ENSO events, in boreal summer monsoon period (JJAS). Among these events positive Indian Ocean Dipole and positive phase of ENSO (El Nino) shows similar dipole variation in SSS and precipitation. Where SSS shows an anomalous decrease in West Indian Ocean region and anomalous increase in south-east Indian Ocean region, analogous to increased and decreased precipitation in respective areas.

The current study also finds that SSS over the Indian Ocean exhibits a dipole-like trend as well. Decreasing (Increasing) salinity is observed in the west-central (south-east) Indian Ocean. Extended analysis of the physical parameters shows that the dipole like trend in salinity is driven by similar trend in precipitation. The current study indicates that this dipole like trend is driven by a skewness towards El Niño and Positive IOD events.