Ship-based observations significantly underestimate carbon dioxide outgassing in the high-latitude Southern Ocean

It is widely believed that the Southern Ocean accounts for a significant portion of the oceanic uptake of anthropogenic carbon dioxide (CO₂). However, flux estimates in this region are based on sparse ship-based observations that are strongly biased towards summer. A new study published in Geophysical Research Letters presented new estimates of Southern Ocean air‐sea CO₂ fluxes based on measurements from biogeochemical profiling floats during 2014‐2017. Compared to ship‐based CO₂ flux estimates, the float‐based fluxes find significantly stronger outgassing in the zone around Antarctica where carbon‐rich deep waters upwell to the surface ocean. These results suggest that our current understanding of the distribution of oceanic CO₂ sources and sinks may need revision and underscore the need for sustained year‐round biogeochemical observations in the Southern Ocean.

Gray, A., K.S. Johnson, S.M Bushinsky, S.C. Riser, J.L. Russell, L.D. Talley, R. Wanninkhof, N.L. Williams, and J.L. Sarmiento. (2018), Autonomous biogeochemical floats detect significant carbon dioxide outgassing in the high‐latitude Southern Ocean, Geophysical Research Letters, 45. https://doi.org/10.1029/2018GL078013.