Oxygen isotope distribution at shallow to intermediate depths across different fronts of the Southern Ocean: Signatures of a warm-core eddy

Abstract

Southern Ocean, an important component of the earth׳s climate system, is changing in response to the anthropogenic climate change. To understand better the dynamics of the Southern Ocean, we documented oxygen isotopic variability and its relation to salinity, especially at intermediate depths (to 1000m) across different fronts, at six stations in the Southern Ocean. Signatures of a warm-core eddy extended from 40 to 44°S and 56 to 59.5°E. It consisted of Subtropical Surface Water (STSW). Other water masses identified were the Antarctic Surface Water (AASW), Antarctic Intermediate Water (AAIW), and Upper Circumpolar Deep Water (UCDW) based on the salinity, temperature and oxygen isotopic ratios. The slope of the oxygen isotope-salinity relationship indicates that the water in the warm-core eddy was derived from a region dominated by evaporation/precipitation while the water surrounding the eddy came from a region dominated by melting/freezing. The shoaling of AAIW up to water depth of 500m was observed along the transect. These new oxygen isotope data, especially from the intermediate depths, will also help fill existing gaps in the global seawater oxygen isotope dataset.