Southern Ocean [in “State of the Climate in 2020”]

The Southern Ocean (SO) plays a unique role in the climate system and is responsible for 40% of oceanic anthropogenic carbon dioxide (CO2) uptake and 75% of the ocean's uptake of heat from the atmosphere (Frolicher et al. 2015). The relatively recent increases in deployments of biogeochemical floats (Claustre et al. 2020), Saildrone Uncrewed Surface Vehicles (USVs; Sutton et al. 2021), and Deep Argo (Roemmich et al. 2019) have provided novel insights into seasonal and interannual variability in SO properties and fluxes. Here, we present 2020 anomalies of SO air–sea heat and CO2 fluxes and show recent changes in mixed layer (ML) and Antarctic Bottom Water (AABW) properties.