Relative abundance and opal input of radiolarians measured on sediment core PS1768-8 and PS2498-1

We present a new proxy, the oxygen isotope measurements (d18O) of radiolarian opal from sediment cores in the Subantarctic Zone (SAZ) and Permanent Open Ocean Zone (POOZ) of the Atlantic Southern Ocean. The SAZ core records of radiolarian and foraminiferal d18O are well correlated. In the POOZ core, only radiolarian 18O shifts to distinctly lower values during the glacial (when this core was in the Sea Ice Zone (SIZ)), while relevant foraminiferal and diatomaceous d18O records exhibit no such shift. This suggests a seasonal salinity change derived from the melting of snow accumulated on sea ice. We propose that a northward relocation of the Southern Ocean zonal system and enhanced water-vapor transport from lower latitudes forced the development of a stratified sea-surface in the northern SIZ during late glacial spring time. This raises unexpected aspects for numerical modeling of past atmospheric coupling and moisture transport, as well as on glacial Southern Ocean stratification and its implication for ocean/atmosphere gas exchange, water mass generation and productivity.