Oxygen isotope–salinity relationships of discrete oceanic regions from India to Antarctica vis-à-vis surface hydrological processes

Abstract Coupled measurements of the oxygen isotope and salinity of surface waters at every degree latitude along a transect from India to Antarctica during summer 2010 were carried out to gain insight into the surface hydrological processes active in the Indian and Southern Oceans. It is possible to identify discrete water masses from the Indian and Southern Oceans based on oxygen isotope and salinity. We determine the relationship between oxygen isotope and sea surface salinity (δ 18 O–SSS) pertaining to those distinct water masses by combining our data with those available at the NASA-GISS data center. These relationships are predominantly governed by evaporation/precipitation except in the Antarctic Zone (beyond Polar Front) where sea ice melting/freezing plays a dominant role. We obtain more representative, long-term mean values of the slopes and intercepts of the salinity–oxygen isotope relation that will help to determine paleosalinity from carbonate fossils from sediments more accurately. The Subtropical and Polar Fronts were identified at 44° S and 54° S, respectively. These new data will also be useful to fill the gap in the existing global gridded δ 18 O data sets obtained by interpolating the observed values.