Effect of land-ice melting and associated changes in the AMOC result in little overall impact on oceanic CO₂ uptake

The impact of Greenland Ice Sheet (GIS) melting and associated weakening in the Atlantic Meridional Overturning Circulation (AMOC) on carbon uptake is quantitatively evaluated using coupled climate and biogeochemistry models. We compare two 140-yr global warming scenarios, forced by the same increase in atmospheric CO₂, but with different GIS melting rates. The AMOC weakening in our 2 scenarios is -47% and -21% at 4 × CO₂ when the melting of GIS is or is not considered, respectively. We find that GIS melting and AMOC-induced weakening have little influence on the CO₂ uptake. By isolating the specific effects of salinity and temperature changes on carbon uptake, we find that opposing processes tend to limit the effect of GIS melting. Indeed, in the GIS melting scenario, less saline and cooler waters in high latitudes northern seas tend to increase CO₂ uptake and counter-balance the decreasing CO₂ uptake that follows from circulation changes alone.