Strengthening winds in Southern Ocean storms are changing the two-way air-sea exchanges of carbon and heat. These spatially and temporally varying fluxes are vital to Earth’s climate system as the ocean moderates the pace of carbon and heat increases in the atmosphere during the ongoing transient response to anthropogenic forcing. Unfortunately, we cannot observe either air/sea carbon fluxes or the winds that drive them directly from satellite. Our global carbon budget calculations rely on reanalysis winds as our proxy for the true wind field, and the latest estimate is that 50% of the global uncertainty in air/sea carbon exchange is associated with the Southern Ocean. However, several studies have shown that reanalysis winds – from all the available datasets – systematically underestimate the strength of both the mean and the extreme winds in storms. We present results from an experiment using the Biogeochemical Southern Ocean State Estimate designed to determine the Southern Ocean air/sea carbon fluxes consistent with hourly winds 20% stronger than the ERA5 reanalysis. We find that higher winds imply increased outgassing, especially in winter, and reduced net uptake of atmospheric carbon by the Southern Ocean.

The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)