Air–sea heat flux in the Southern Ocean: insights from 13 years of Southern Ocean Flux Station (SOFS) observations

This study examines over 13 years (March 2010 to May 2023) of data from 12 Southern Ocean Flux Station (SOFS) mooring deployments to explore the characteristics and temporal climatology of air–sea heat flux in the Southern Ocean. SOFS, the only currently operational moored buoy in the Southern Ocean (anchored at ~47°S, 142°E), provides high-resolution (1-min) climate-quality meteorological and marine data, facilitating detailed air–sea heat flux analysis. Before analysis, the 1-min SOFS flux data were rigorously evaluated, and their high quality confirmed by comparing net heat flux against nearby overlapping moorings and research vessels. Over the study period, the average annual net heat flux at the SOFS site is −14.6 ± 5.4 W m−2 (a net ocean heat gain). This is the first estimate of the net heat exchange at a Southern Ocean site that is based on a multi-year record of high-quality measurements, offering direct evidence of the ocean region’s absorption of heat. Seasonal heat flux variabilities and extreme heat flux events are investigated. Additionally, a case study highlights a strong horizontal sea surface temperature gradient (3.4°C over 35.5 km) that resulted in a significant net heat flux difference of up to 242.5 W m−2, which showed that the environmental conditions in this region may shift dramatically over short temporal or spatial scales.