Deep mesoscale eddies in the Southern Ocean drive heat poleward at levels reaching the same order of magnitude as surface transport, according to research published in Nature Communications. Researchers used Argo float observations and sensitivity experiments to quantify deep eddy kinetic energy and eddy meridional heat transport.
The measurements show that deep eddy meridional heat transport matches surface transport in magnitude, even though deep eddy kinetic energy registers at only one-fifth of surface levels. Sparse in situ observations had previously restricted estimates of eddy meridional heat transport to the near surface, leaving deep ocean processes poorly quantified.
Float observations and sensitivity experiments revealed that deep eddy heat transport shifts subtropical warm waters toward Antarctica by more than ten degrees of latitude relative to mean-flow transport alone. About 60% of this deep transport originates in the Indian Ocean sector.
Researchers Tongya Liu, X. Zhai, Q. He, and Andrew McC. Hogg conducted the study with collaborators across institutions in China, the United Kingdom, and Australia. Participating institutions included the Second Institute of Oceanography under China's Ministry of Natural Resources, the University of East Anglia, the South China Sea Institute of Oceanology, and the Australian National University.
The peer-reviewed paper was submitted on January 5, 2026, accepted on August 4, 2026, and published on August 12, 2026. Research funding came from the National Key R&D Program of China, the Scientific Research Fund of the Second Institute of Oceanography, the National Natural Science Foundation of China, the Key R&D Program of Zhejiang Province, and the Impact and Response of Antarctic Seas to Climate Change Program.
