IUGG 2003 Abstract

P05-Posters The Physical Oceanography of the Indian Ocean Monday, June 30 PM Location: Site D

TIME [ 1645-261 ] [ P05/30P/D-005 ] [ Poster ]

CROSS-EQUATORIAL SECTION AT 77Z�°E IN THE INDIAN OCEAN: HYDROGRAPHY AND OBSERVED CURRENTS DURING NOVEMBER 2002

Murty Suryanarayana VADLAMANI(National Institute of Oceanography)

Babu Ramesh V.(National Institute of Oceanography) Kumari Krishna L. ( National Institute of Oceanography ) Sugandha SARDESSAI ( National Institute of Oceanography ) Lina P. MERGULHAO ( National Institute of Oceanography ) Soniya SUKUMARAN ( National Institute of Oceanography ) Cathrine J. SUMATHI ( National Institute of Oceanography ) Nisha S. PIRES ( National Institute of Oceanography ) Antony M.K. ( National Institute of Oceanography ) Somayajulu Krishna Y. ( National Institute of Oceanography ) Krishnamacharyulu R.J. ( National Institute of Oceanography )

As part of the Indian Ocean Global Observing Ocean System (IOGOOS) program, multi-disciplinary oceanographic observations (physical, biological, chemical and geological) were made along the 77Z�°E cross-equatorial section between 5Z�°S and 3Z�°N during northern Fall (10-29 November, 2002) onboard ORV Sagar Kanya. In situ primary productivity was measured at eight depths in the upper 120 m at 2Z�°S, 77Z�°E and 0.5Z�°N, 77Z�°E, in addition to the measurements made on surface productivity by deck incubation. Analysis of the data revealed the presence of a strong (120-150 cm/s eastward velocity) Fall Equatorial Jet in the upper 100 m between 1Z�°S and 2Z�°N with its core located at 1Z�°N. The transport of the Jet in the upper 100 m water column was about 22x106m3/s, advecting warm (>28Z�°C), high saline (>35.6 psu) Arabian Sea waters towards east. On the northern and southern boundaries of the Jet, the westward flowing North Equatorial Current (NEC) and South Equatorial Current (SEC) were identified. An intense divergence zone was developed due to strong current shear between the Jet and the NEC. The Jet and the associated turbulent mixing thickened the mixed layer and deepened the thermocline, while the mixed layer thinned and shoaled to the north and south of the Jet. More interstingly, the influence of the Fall Equatorial Jet on the variation of biogeochemical parameters in the upper ocean north of the equator is discussed.