The Southern Ocean connects all major ocean basins and plays a pivotal role in the meridional overturning circulation of 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 Japanese Antarctic Research Expedition, Umitaka-maru have annually observed high-quality conductivity-temperature-depth (CTD) and water sampling data (salinity, dissolved oxygen, and nutrients) along a 110°E transect in January. Sea surface temperature and salinity were obtained continuously with a thermosalinograph (TSG) along the cruise track between the ports of Fremantle and Hobart. 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. This report presents the latest data collected in 2020 and is the fourth report for this journal, of which the first presented data collected in 2017.
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