Increasing trends in oceanic surface poleward eddy heat flux observed over the past three decades

Mesoscale processes make the largest contribution to ocean variability and are significant agents in ocean heat transport. In this investigation, we provide evidence based on satellite observations for an increasing trend in surface transient eddy heat flux (EHF) over the period 1993-2020. The enhanced EHF is particularly prominent in western boundary currents and their extensions at mid-latitudes, with increases of 20%-40% per decade. Additionally, we decompose the EHF trend into contributions from velocity variance, temperature variance and a coherence parameter using a Cauchy-Schwarz inequality. We find that each contributes to the spatial pattern of the trend in EHF, with the contribution from enhanced temperature variance dominating the global zonal mean EHF trend over the past few decades.