The authors present the first synoptic characterisation of an oceanic mesoscale eddy’s full life cycle using groundbreaking SWOT satellite altimetry. This unprecedented view challenges the long-standing perception of eddies as simple, elliptical structures, revealing the crucial role of mesoscale interactions in their evolution. The SWOT results capture intense submesoscale turbulence at the eddy’s rim, exposing secondary instabilities that likely drive its dissipation. These findings not only validate decades of vortex theory but also open new frontiers in our understanding of oceanic turbulence.

This paper thoroughly describes the data processing steps and assessment of the usefulness of the new SWOT mission for advancing ocean science. The paper will be of great interest the ocean and sea ice communities and others. The discussion of the benefits, relevance, and limitations of Level-3 swath-altimeter products for various research domains is particularly important.

The study introduces an innovative method for estimating meridional heat transport (MHT) across latitudes. By combining diverse oceanographic approaches, including remote sensing (gravimetry, altimetry), in-situ observations, and advanced statistical modeling, the study bridges several domains of ocean science. It opens the door for things such as an improved estimation of ocean heat content, surface fluxes, sea level variability, currents and enhanced error characterization in satellite observations. The new method could serve as the foundation for alternative estimates of both MHT and the Atlantic Meriodional Circulation (AMOC) that do not depend on costly, geographically limited in-situ observing arrays, which is especially beneficial if it allows the AMOC to be observed across a range of latitudes.