The imprint of mesoscale eddies on the sea surface temperature field and its associated heat transport

An observational estimate of mesoscale eddy sea surface temperature (SST) imprints, central to mesoscale heat transports and eddy-atmosphere coupling, is provided for North Atlantic and Southern Ocean by analyzing the relationship between satellite microwave SST and independent multi-altimeter sea surface height (SSH) observations. The analysis is carried out at fixed-location and also following eddy tracks.

At fixed location, SST variability is observed to feature narrow bands of enhanced mesoscale control anchored at major current fronts of Gulf Stream and Antarctic Circumpolar Current (ACC). Large-scale atmospheric forcing, which dominates SST variability in the adjacent subtropical gyre interiors, is also found to be important in the ACC and the Gulf Stream.

Following eddies' tracks allows to detect transient mesoscale SST imprints that clearly stand out from the large-scale, atmospherically forced SST signals, even in regions of weak SSH variability. The track-following analysis reveals robust westward phase-shifts of eddies' SST anomalies with respect to their rotating cores everywhere. In energetic regions the observed intense warm-top anticyclones and cold-top cyclones are only nearly in-phase, whereas in quiet regions weaker SST signatures are almost in quadrature with eddies' SSH. Propagating eddies thereby flux heat poleward in the mixed-layer over a broad range of oceanic regimes, in a manner qualitatively consistent with linear models of baroclinic instability. The data analysis furthermore suggests that the coherent displacement of the warm/cold eddies down the mean temperature gradient acts as an additional contributor to mesoscale heat transport in regions of enhanced SSH variability.