Mechanisms of subpolar gyre variability in CMIP6

The subpolar gyre (SPG) is one of the regions in the North Atlantic ocean where convection takes place. It has been indicated as one of the earth system’s tipping elements that is closest to crossing its threshold due to global warming, which also could impact the Atlantic Meridional Overturning Circulation (AMOC). Therefore, understanding the mechanisms of its variability is of key importance to learn about possible changes under global warming. We use causal inference to study the mechanisms of convection in the SPG region in CMIP6 models. Causal inference goes beyond correlation, by taking into account common drivers and other possible confounding factors, to establish causal links between variables. We find that the interaction between convection and density is well represented in most models, whereas a link of both to the circulation strength of the gyre is captured by fewer models. These results provide valuable information on the capability of CMIP6 in representing SPG variability, and form a starting point for investigating possible links with the AMOC.