Stronger Oceanic CO₂ Sink in Eddy-Resolving Simulations of Global Warming

Accurately representing the ocean carbon cycle in Earth System Models (ESMs) is essential to understanding the oceanic CO₂ sink evolution under CO₂ emissions and global warming. A key uncertainty arises from the ESM's inability to explicitly represent mesoscale eddies. To address this limitation, we conduct eddy-resolving experiments of CO₂ uptake under global warming in an idealized mid-latitude ocean model. In comparison with similar experiments at coarser resolution, we show that the CO₂ sink is 34% larger in the eddy-resolving experiments. 80% of the increase stems from a more efficient anthropogenic CO₂ uptake due to a stronger Meridional Overturning circulation (MOC). The remainder results from a weaker reduction in CO₂ uptake associated to a weaker MOC decline under global warming. Although being only a fraction of the overall response to climate change, these results emphasize the importance of an accurate representation of small-scale ocean processes to better constrain the CO₂ sink.