Accurate estimates of the air-sea CO₂ flux in the Southern Ocean are crucial to make progress in understanding the global ocean carbon cycle and reducing uncertainties, but it is still unclear due to the sparse shipboard observations in time and space. The emerging novel biogeochemical Argo float equipped with pH-sensor fills an important gap by presenting CO₂ partial pressure (pCO₂) and CO₂ flux estimates in this undersampled region since 2014. The floats have identified a significantly larger-than-previously-estimated CO₂ outgassing to the atmosphere in the high-latitude Southern Ocean, which challenges the conventional view that the Southern Ocean accounts for 40% of global oceanic CO₂ uptake. However, this result remains controversial and needs urgent validation because it contradicts some new evidences supporting the strong Southern Ocean CO₂ sink as with shipboard observations.

Southern Ocean,Biogeochemical Argo float,Ocean carbon sink