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%). Our findings indicate that STG heat transport cannot be meaningfully distinguished from that of the basin-scale overturning since water parcels cooled within the gyre subsequently feed the northward, subsurface limb of the AMOC.