Distinct Vertical Structures of Global Eddy Heat and Salt Transports Revealed by Altimetry and Argo Observations

Abstract Mesoscale eddies play a key role in redistributing oceanic heat and salt, yet their global three‐dimensional (3D) transport structures remain poorly understood. Here, we estimate global meridional eddy heat and salt transports in the upper 1,800 m from satellite altimeter and Argo observations, revealing distinct vertical structures. Eddy heat transport reverses with depth, being poleward in the upper ocean but equatorward below, resulting in strong vertical cancellation and a weak net contribution to total meridional heat transport. In contrast, eddy salt transport exhibits pronounced latitude dependence, weakly equatorward at low latitudes but strongly poleward at mid‐latitudes, where it contributes nearly half of the total meridional salt transport. These contrasting behaviors primarily arise from differences in background temperature and salinity gradients, consistent with down‐gradient eddy fluxes. Our results provide novel observational insights into the global 3D structures of eddy heat and salt transports, offering a benchmark for evaluating ocean and climate models.