• G S Sharma

      Articles written in Journal of Earth System Science

    • Incursion of the Pacific Ocean Water into the Indian Ocean

      G S Sharma A D Gouveia Shubha Satyendranath

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      Using the data collected during the International Indian Ocean Expedition, maps showing the distribution of depth, acceleration potential, salinity and oxyty were prepared for the northeast monsoon for the four potential thermosteric anomaly surfaces: 160, 120, 80 and 60 cl/t. Zonal components of current aong 84°E were computed from the geopotential dynamic heights. From such an analysis, it became clear that low-salinity water from the Pacific intrudes into the western Indian Ocean through the Banda and Timor seas in the upper layers above 100 cl/t surface, while the North Indian Ocean Water penetrates towards the Eastern Archipelago below 100 cl/t surface. The South Equatorial Countercurrent and the Tropical Countercurrent are well depicted on the vertical section of zonal components as well as on the distribution of acceleration potential.

    • Hydrography and circulation off the Antarctica in the Indian Ocean region

      G S Sharma Basil Mathew

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      The hydrography and circulation pattern off Antarctica in the Indian Ocean region are studied using vertical sections of temperature, salinity and oxyty approximately along 20°E, 77°E and 90°E, and the dynamic topography of the sea surface with reference to 1000 db. Based on the oceanographic characteristics, the whole region under study can be divided into three zones, the extreme ends being characterised by the frontal structure. The dicothermal layer is conspicuous during summer south of 50°S. The surface flow around Antarctica is mainly zonal. The East Wind Drift, found as a narrow westward flow near Antarctica, is observed at a lower latitude in the eastern Indian Ocean where the land extends northword. Contrary to expectation there is evidence of a westward flowing surface current at about 35°S between 45°E and 65°E.

    • Internal wave characteristics in the eastern Arabian Sea during summer monsoon

      P G K Murthy G S Sharma V V James K V Suseela

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      The time series BT profiles and surface winds and atmospheric pressure, collected in the deep waters off Ratnagiri and Karwar during summer monsoon were utilized to document the characteristics of internal waves (IW). Low-frequency (≤2, cycle per day (cpd)) IW off Ratnagiri are found to propagate at 83 cm/s with wavelengths of 45 km and wave heights upto 40 m. These parameters for high-frequency (>2 cpd) IW off Karwar correspond to 99 cm/s, 3 km and 23 m. The IW off Karwar appear to leave the station at 70° (±10°) (measured from the horizontal). The data sets were further analysed to address the harmonic composition of the IW and identify the possible sources for the observed IW fields. Power spectra of the IW indicated energy peaks at inertial (0·6 cpd) and tidal (1 and 2 cpd) frequencies off Ratnagiri and in the high-frequency band of 0·5–2·0 cycles per hour off Karwar. The coherence between the IW and wind/tide is found to be good at several frequencies within the IW spectrum. This feature probably suggests tides as a source for the IW of tidal frequencies and winds and tides as a joint source for the IW at the remaining frequencies.

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