Thermal Imprints of Mesoscale Eddies in the Global Ocean

Mesoscale eddies have been widely documented for their significant fi cant role in regulating oceanic heat absorption and redistribution. However, our understanding of their thermal impacts on a global scale has been hampered by the scarcity of eddy-targeted observations. Here, we perform a comprehensive global analysis of over 2 million historical hydrographic profile fi le measurements collocated with satellite-based eddy observations between 1993 and 2019, revealing rich geographical variability in the intensity, vertical extent, and asymmetry of the temperature anomalies induced by eddies. In tropical and subtropical oceans, temperature anomalies within eddies are dominated by eddy pumping and heavily influ- fl u- enced by near-surface vertical stratification, fi cation, resulting in a relatively shallow extent of eddy effects (around 500 m) with subsurface maximum temperature anomalies occurring near 100 m. In midlatitude main current systems with sharp horizontal temperature gradients, the impact of eddy trapping becomes evident, leading to temperature anomalies extending to depths of 1000 m, with vertical peak values exceeding 4 degrees C degrees C between 300 and 700 m, equivalent to perturbations in the local mean-state temperature of nearly 30%. This process also results in substantial temperature anomalies on isopycnal surfaces, indicating notable cross-frontal transport of heat and water mass with varying properties. The estimated meridional heat transport by eddy movement is on the order of O (1) MW, generally one order of magnitude smaller than previous estimates of the time-varying meridional heat transport (V'T'). V ' T ' ). However, this does not imply that they are unimportant, as this long-range cross-frontal heat transport may have significant fi cant consequences on regional temperature extremes and biogeochemical environments.