Mesoscale Meridional Heat Transport Inferred From Sea Surface Observations

The ocean regulates the Earth's climate by transporting heat from the equator to the poles. Here, we use satellite‐based sea surface observations of air‐sea heat fluxes and eddy detection to investigate the mesoscale heat transport. “Mesoscale” refers to both the Eulerian perspective as the spatio‐temporal scales of ∼100 km and ∼1 month, as well as the Lagrangian aspect as isolated vortices identified from the dynamic topography. Paradoxically, there are a considerable number of mesoscale eddies inconsistent between their surface thermal and dynamic signals, that is, cold‐core anticyclones and warm‐core cyclones are globally prevalent. On account of such inconsistency, we show that the mesoscale meridional heat transport carried by geostrophic components is 10 times larger than (and opposite in direction to) that of the wind‐driven Ekman components. An offset between SSH‐SST coherent and incoherent eddies in the Ekman heat transport is apparent, whereas the geostrophic heat transport is contained within coherent eddies. Plain Language Summary Rotating water masses in the ocean, termed as mesoscale eddies, are dynamically important features because they can transport nutrients and displace heat in the Earth's climate system. In the same manner as the atmospheric weather systems that are associated with high or low pressures, mesoscale eddies are accompanied by sea level anomalies and therefore can be observed by satellite images. Conventionally, anticyclonic eddies detected as clockwise vortices in the Northern Hemisphere display warm temperature anomalies at the center. However, recent studies have found that the sea surface temperature signal of an eddy might be uncertain and even contradictory to their dynamical circulation patterns. In this study, we combine sea surface observations of temperature and velocity fields to determine the patterns of global ocean heat transport associated with mesoscale eddies. Key Points The geostrophic component of meridional heat transport (MHT) at the mesoscale is 10 times larger than the Ekman component SSH‐SST coherent eddies dominate the spatial patterns of MHT at the mesoscale Though incomparable in magnitude with the large scale MHT, mesoscale eddies can still transport 30 TW of heat near sea surface