Feedbacks between ocean circulation and the carbon cycle: a present and future perspective
The ocean carbon sink currently mitigates the continuing build-up of carbon dioxide in the atmosphere by absorbing approximately 30% of all additional CO2 derived from human activities. Within the Atlantic, the overturning circulation plays a key role, driving the carbon uptake associated with biological productivity (transporting nutrients to productive regions) and the physical carbon pump (heat fluxes changing CO2 solubility of surface waters), while also supplying large quantities of old remineralised carbon to the surface where it is outgassed to the atmosphere. It also transports surface waters replete with high levels of anthropogenic carbon to depth on climatically important timescales. While decadal variation in the overturning circulation has recently been linked to changing global carbon uptake patterns, knowledge about their correspondence over shorter timescales is in its infancy. Here we investigate what current observations show us about how the biological and carbon systems respond to circulation variability over multiple timescales, how models currently perform in replicating this, and what the future holds.