Summary of Abstract Submission

Abstract Submission No. IO50-07-0020PresentationOral

ON THE VARIABILITY OF SUB-SURFACE AND DEEP-OCEAN CURRENTS AND TEMPERATURE IN THE EQUATORIAL INDIAN OCEAN DURING 2010-14

Murty V.S.N.*1, Suryanarayana A.1, Gayatri Vani D.1, Steeven Paul Y.1, Ganapathi P.1, Anjaneyulu C.1, Goankar M.G. 1, Satlekar N.P.1, Almedia Anselm M.1, Tari A.P.1

1 CSIR-National Institute of Oceanography, India

ABSTRACT :

Long-term current measurements program in the Equatorial Indian Ocean (EIO) was initiated by CSIR-NIO in the year 2000 with the first deployment of the current meter mooring at Equator, 93E. Subsequently, an array of 7 deep-sea moorings across (1N, 77E; 1S, 77E; 1N, 93E; 1S, 93E) and along the equator (Eq., 77E; Eq., 83E; Eq., 93E) was established for the sustained long-term current and temperature measurements. This study forms part of this observational program. Analysis of the currents and temperature data during 2010-14 along and across the equator reveals intraseasonal and interannual variability. The Equatorial Fall jet was strong (120-140 cm/s) during November-December 2010 and weak in November-December 2011, under the impact of the dynamics associated with the prevailing negative Indian Ocean Dipole (IOD) event in 2010 and positive IOD in 2011. The Equatorial Undercurrent (EUC) during March-April showed variability in its speed (60-80 cm/s) and depth (100 - 200 m). The upper layer (60-300 m) volume transport per unit distance showed higher zonal volume transport with semi-annual variation. A new insight in the Equatorial dynamics at intraseasonal time scales is revealed with the presence of biweekly (10-20 day) oscillations across the equator at 1N and 1S at 77E and 93E over longer distances (110 km) on either side of the equator. It can be interpreted that the energy associated with the surface wind forced Mixed Rossby Gravity (MRG) waves propagate downward also away from the equator, affecting the deep-water circulation and temperature in the deeper regions of the EIO.