Contribution of Unconventional Mesoscale Eddies to Surface Poleward Heat Flux in the Southern Ocean Over the Past Three Decades

Abstract Mesoscale eddies play a key role in transporting heat poleward across the Antarctic Circumpolar Current (ACC). In addition to conventional eddies (warm‐core anticyclones and cold‐core cyclones), recent studies have detected a significant number of unconventional eddies at the surface (cold‐core anticyclones and warm‐core cyclones). Using satellite observations from 1993 to 2021, this study investigates how these unconventional eddies contribute to surface poleward eddy‐induced heat flux (EHF) in the Southern Ocean. We find that unconventional eddies make a positive contribution to total EHF, but the EHF induced by a composite unconventional eddy is only half of that induced by a composite conventional eddy. While there has been an increasing trend in total EHF over since 1993, the contribution from unconventional eddies has decreased from 25% to 15% due to a decline in their number. Our findings demonstrate the importance of understanding the contribution of unconventional eddies to the EHF and its changes.