Oxygen isotope and salinity variations in the Indian sector of the Southern Ocean

Abstract

A combined study of stable oxygen isotopes (δ¹⁸O) and salinity of surface ocean waters collected from the Southern Indian Ocean during the late austral summer and early fall (25th January to 1st April, 2006) helped to trace atmospheric and oceanic processes: near the equator, a very clear signature of the domination of evaporation-precipitation process was seen, while a precipitation dominated zone was located between two evaporation dominated zones south of the equator. The signature of the Agulhas Front (AF) and the Subtropical Front (STF, recognizable by the sharp decrease in salinity and δ¹⁸O) in the surface waters were identified at 41°S and 44°S in February; during the return journey (March) these two fronts had merged and were located at 41°S. South of 45°S, the slope of the δ¹⁸O-salinity relationship was close to zero; while north of 62°S could have some precipitation/evaporation effect, south of 63°S was clearly dominated by freezing/melting.