Utilizing two-dimensional sea level anomalies from the Surface Water and Ocean Topography (SWOT) wide-swath altimeter, we conduct a global census of fine-scale eddies (with equivalent radii < 30 km) that are beyond the resolution capacity of traditional altimeters. We find that these eddies are concentrated in regions with energetic mesoscale currents such as western boundary current extensions, the Antarctic Circumpolar Current and prominent interior frontal zones. While these eddies are smaller than classical mesoscale eddies (O(100) km), they exhibit dynamics distinct from the mesoscale, including a pronounced winter peak in occurrence frequency and a striking dominance of cyclonic over anticyclonic polarities. A global composite reveals a net enhancing effect of these fine-scale eddies on surface chlorophyll-a (approximately +7% within eddy cores relative to surrounding waters). Our findings shed light on the dynamical characteristics and surface chlorophyll-a signatures of fine-scale ocean eddies, necessitating their adequate representation in next-generation ocean models.
Mesoscale eddies in the Southern Ocean extend from the surface to the deep ocean and contribute to regional and global ocean heat budgets. However, sparse in situ observations have limited estimates of eddy meridional heat transport (EMHT) to the near surface, leaving deep-ocean processes poorly understood. Here we quantify deep eddy kinetic energy (EKE) and EMHT using Argo observations. We find that deep EMHT reaches at least the same order of magnitude as surface transport, despite deep EKE being only one-fifth of surface levels. Float observations and sensitivity experiments reveal that, relative to mean-flow transport alone, deep EMHT extends the meridional movement of subtropical warm waters towards Antarctica by over ten degrees of latitude. About 60% of this deep transport originates from the Indian Ocean sector. These findings provide observational evidence that mesoscale eddies can modulate deep Southern Ocean heat redistribution, with potential implications for Antarctic climate.
Tongya Liu, Xiaoming Zhai, Qingyou He et al.· Nature Communications· 0 citations