Physical and chemical oceanographic data during Umitaka-maru cruise of the 64th Japanese Antarctic Research Expedition in January 2023

The Southern Ocean connects all major ocean basins and plays a pivotal role in the meridional overturning circulation of the global oceans. High-quality physical (temperature, salinity, and dissolved oxygen) and chemical (nutrients) oceanographic data from the Southern Ocean are thus critical for an improved understanding of future climates. As part of the 64th Japanese Antarctic Research Expedition, and also as a part of annually conducted monitoring observations, we have obtained high-quality Conductivity-Temperature-Depth (CTD) and water sampling data (salinity, dissolved oxygen, and nutrients) at 9 sites located along a 110E transect in January 2023. Sea surface temperature and salinity were obtained continuously with a thermosalinograph (TSG) along the cruise track between the ports of Fremantle and Hobart, except within the Australian Exclusive Economic Zone. Data quality was validated by following as far as possible the recommendations for instruments and methods of the Global Ocean Ship-Based Hydrographic Investigation Program.