Stable isotopes of oxygen in seawater (δ¹⁸O) on A23 repeat hydrographic section, occupation in January-February 2017 (JR16004).

The A23 repeat hydrography section is fortuitously positioned for studies of Southern Ocean freshwater changes. Within the Scotia Sea, it spans the southernmost front of the Antarctic Circumpolar Current (the Southern ACC Front, SACCF, which loops anticyclonically around South Georgia from the south), and also the Southern Boundary of the ACC. Further south, the section crosses the northern limb of the Weddell Gyre, a region of predominant sea ice melt and downstream in the cyclonic circulation from the major ice production sites in the southern Weddell Sea. Separating these two regimes is the Weddell-Scotia Confluence, which lies above and close to the topography of the South Scotia Ridge and which feature waters of unusually low vertical stratification. To better determine the sources of freshwater injection into this complex oceanographic regime, we sampled and measured the stable isotopes of oxygen in seawater (δ¹⁸O) during the ORCHESTRA cruise JR6004 in January-February 2017 . These measurements enable the partitioning of freshwater into a component due to sea ice melt, and a component due to meteoric water inputs (glacial melt and precipitation combined). These data will aid with understanding the oceanic impact of interannual and decadal changes in Southern Ocean sea ice, and freshwater injection to the ocean from melting ice sheets and icebergs.