Detecting the anthropogenic influences on recent changes in ocean carbon uptake

Anthropogenic greenhouse gas emissions have modified the rate at which oceans have absorbed atmospheric CO₂ over the last centuries through rising atmospheric CO₂ and modifications in climate. However, there are still missing pieces in our understanding of the recent evolution of air-sea CO₂ exchanges related to the magnitude of their response to anthropogenic forcings versus that controlled by the internal variability. Here, to detect and attribute anthropogenic influences on oceanic CO₂ uptake between 1960 and 2005, we compare an ensemble of Coupled Model Intercomparison Project Phase 5 (CMIP5) climate model simulations forced by individual drivers to ocean-only model reconstructions. We demonstrate that the evolution of the global oceanic carbon sink over the last decades can be understood without invoking climate change, attributing rising atmospheric CO₂ as prominent driver of the oceanic sink. Nonetheless, at regional scale, the influence of climate change on air-sea CO₂ exchanges seems to emerge from the internal variability within the low-latitude oceans.