The Atlantic Meridional Overturning Circulation (AMOC) plays a critical
role in the global climate system through the redistribution of heat,
freshwater and carbon. At 26.5N, 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
26.5N. We find that water parcels recirculating
within the STG account for 37% (0.36 PW) of the total heat transport
across 26.5N, 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.