Abstract
The Atlantic Meridional Overturning Circulation (AMOC) plays a critical
role in the global climate system through the redistribution of heat,
freshwater and carbon. At 26.5oN, the
meridional heat transport has traditionally been partitioned
geometrically into vertical and horizontal circulation contributions;
however, attributing these components to the AMOC and Subtropical Gyre
(STG) flow structures remains widely debated. Using water parcel
trajectories evaluated within an eddy-rich ocean hindcast, we present
the first Lagrangian decomposition of the meridional heat transport at
26.5oN. We find that water parcels
recirculating within the STG account for 37% (0.36 PW)
of the total heat transport across
26.5oN, more than twice that of the
classical horizontal “gyre” component (15%). Rather
than being distinct from the overturning circulation, the heat transport
associated with the STG is due to the formation of subtropical mode
waters via a shallow downward spiral, which ultimately feeds the
northward limb of the AMOC.