Changes in MOC and gyre‐induced Atlantic Ocean heat transport

Anthropogenic change of the Atlantic meridional ocean heat transport (AOHT) is diagnosed from a large ensemble of climate simulations over the period 1940–2080, as well as its relation to changes in the Meridional Overturning Circulation (MOC) and the gyre circulation in the Atlantic. Internal variability in AOHT is closely associated with MOC variability. The anthropogenic change in AOHT, however, does not follow the forced decrease in the MOC. Thermohaline changes in the intermediate and deep water masses that are formed in the subpolar gyre cause the vertical temperature gradient near the western boundary to increase. As a result, the heat transport by the baroclinic gyre component largely compensates the decreased heat transport by the MOC.