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dc.contributorDepartment of Ocean Development, New Delhi, India
dc.contributor.authorNaqvi, S.W.A.
dc.identifier.citationScientific report of third Indian Expedition to Antarctica; 1986; 75-85
dc.description.abstractHydrographical and hydrochemical observations have been made at a shelf station off Princess Astrid Coast, Dronning Maud Land, Antarctica, and at 11 other stations along a transect from Antarctica to about 30~'S latitude. The shelf station, located in a trough, has been occupied at 1 - month interval in January and February. Significant vertical and temporal variations in temperature and salinity are restricted to the upper 200 m; the water is more or less homogeneous below this depth, probably trapped in the trough and renewed by the winter convection. There is some near-surface thermohaline stratification, especially pronounced in January. Substantial warming of surface waters occurs from January to February, resulting in the melting of ice which reduces the surface salinity. A sub-surface oxygen maximum is observed in January associated with a maximum in primary production. Oxygen concentrations at all depths exhibit decreases from January to February in conjunction with increases in nutrients except phosphate, probably resulting from the oxidation of organic matter following high primary production in January. Vertical sections of temperature, salinity, potential density, dissolved oxygen, apparent oxygen utilization, phosphate, nitrate, silicate, pH and alkalinity through Antarctic, subantarctic and subtropical zones are presented and discussed. The Antarctic Divergence is observed appreciably to the south of its previously reported positions around 20~'E longitude, indicating some variability in its position. No large gradients in the sea surface temperatures are observed in the Polar Front Zone, supporting the view that the transition from Antarctic to subantarctic waters is less sharp in the area around Crozet island. Most striking changes in all properties are observed in the transition zone between waters of subantarctic and subtropical types. An oxygen maximum and a pronounced thermostad corresponding to the Subantarctic Mode Water, however, are not observed at any station, probably due to a weakly-developed subantarctic zone south of the subtropical convergence in the area of study. Ths ratio between the changes in nitrate and phosphate is deduced as ~D N: ~D P = 13.6:1 (by atoms), in conformity with some recent data from the Indian sector of the Southern Ocean, suggesting a lower N:P ratio in the biomass than the corresponding oceanic average value (16:1)
dc.relation.ispartofseriesDOD Technical Publication No.3
dc.subjectOceanography and Limnology
dc.subject.otherChemical Properties
dc.subject.otherSurface Temperature
dc.subject.otherISW, Southwest Indian Oean
dc.titleSome oceanographic observations in the polynya and along a section in the southwest Indian/ Antarctic Ocean
dc.typeTechnical Report
dc.affiliation.authorCSIR-National Institute of Oceanography, Dona Paula, Goa, India

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