Summary of Abstract Submission

Abstract Submission No. IO50-08-0026PresentationPoster

INERTIAL AND SUB-INERTIAL OSCILLATIONS IN THE SEYCHELLES-CHAGOS THERMOCLINE RIDGE REGION IN THE SOUTHWEST TROPICAL INDIAN OCEAN

P.Sabu*1, N.Anilkumar1, Jenson V George2, Vinu Valsala3, Racheal Chacko1

1 NCAOR, Goa, India
2 NIOT, Goa, India
3 IITM, Pune, India

ABSTRACT :

The southwest Tropical Indian Ocean (SWTIO) is unique in comparison with the other regions of the Indian Ocean due to its significant sea surface temperature variability in different time-scales. SWTIO exhibits a year-round upwelling (a maximum of upto 6m/day) region maintained by the Ekman pumping driven by the overlying winds, results in near surface thermocline and shallow mixed layer, often referred as Seychelles-Chagos thermocline ridge (SCTR). Several of the previous studies have reported the intra-seasonal, seasonal and interannual variability of the mixed layer and thermocline in the SWTIO and its coupling with the atmosphere. The present study describes an inertial to sub-inertial oscillations of shallow thermocline of the SCTR observed in a 10- day in-situ high resolution (sampled at every 6-hour interval) hydrographic data collected from 8S 67E during June of 2014. Large undulations (5 to15 m/6 hrs) in the thermocline were noticed during this 10-day period of observations. It was also observed that the stratification in the subsurface layer (30-150 m) was remarkably intense (~15 cycle/hour of stability oscillations as inferred by the Brunt-Vaisala frequency) and anticipated to be induced by the fresh water intrusion to the observation location. The observed undulations in the thermocline is possibly due to the internal waves, governed by the high stratification and likely be forced by high wind stress exerted on the sea surface by passage of an atmospheric synoptic scale disturbance during the period of observation. The role of tides on this variability is also elucidated.