Summary of Abstract Submission

Abstract Submission No. IO50-08-0009PresentationOral

PHYSICALLY FORCED FLUCTUATIONS IN DISSOLVED OXYGEN LEVELS IN THE EQUATORIAL INDIAN OCEAN

Shubhendu Dasgupta*1, Satya Prakash2, Ashok Karumuri1

1 University of Hyderabad, India
2 Indian National Centre for Ocean Information Services (INCOIS), India

ABSTRACT :

The equatorial Indian Ocean (EIO) undergoes seasonal thermohaline variations generated by synoptic scale dynamics associated with the Asian monsoon system. There is a higher net influence of physical over biogeochemical processes on dissolved oxygen (DO) in the EIO arising due to a lack of open ocean upwelling and north-south monsoonal wind reversals. The hydrographic parameters are thus essential for analyzing DO levels in the EIO region. Data obtained from an Argo float deployed in the EIO were used to categorize the different water masses.  The data shows an abrupt increase in DO at 300-400 m depth. The DO maxima at such depths exhibits  seasonal and inter-annual variabilities. Our analysis shows that the occurrence and variabilities of such an abruptness are related to the presence of Indian Equatorial Water and its mixing with a relatively low salinity water mass, i.e Antarctic Intermediate Water. Using satellite altimetry data, we have observed a coherence between sea level anomalies, thermocline and oxycline depth anomalies. This indicates that large scale planetary waves propagating on seasonal timescales play an important role in controlling the subsurface temperature and DO levels. The temporal variability of SLA was used to explain the cyclicity in the thermocline and oxycline depths.