Impacts of Salinity Anomalies on Vertical Mixing and SST During Positive IOD Events
[16-Dec-2016] Kido, S. and Tozuka, T.
Presented at the 2016 AGU Fall Meeting
Sea surface salinity (SSS) in the tropical Indian Ocean undergoes large interannual variations associated with the Indian Ocean Dipole (IOD), but their impacts on the upper-ocean stratification and sea surface temperature (SST) are not fully understood. Here, using a 1-D turbulence closure model, a series of sensitivity experiments with and without salinity anomalies is carried out to quantify their impacts during positive IOD events.
In the central-eastern tropical Indian Ocean, a combination of negative SSS anomalies and positive subsurface salinity anomalies strengthens the upper ocean stratification during positive IOD events. As a result, vertical mixing is suppressed and significant warming of ~0.5â occurs. On the other hand, weakening of salinity stratification caused by near surface positive salinity anomalies in the southwestern tropical Indian Ocean enhances vertical mixing and results in cooling (~-0.2â). Our results suggest that variations in salinity stratification may potentially play a crucial role in the evolution of positive IOD events.