High-latitude eddy statistics from SWOT compared with in situ observations

Abstract

Mesoscale eddies play a key role in the transport of heat, salt, and momentum in the ocean, yet their statistical characterization at high latitudes has remained elusive due to the coarse resolution of conventional satellite altimetry. Here we present a statistical description of the mesoscale eddies in the Labrador Sea at an unprecedented resolution, using observations from the Surface Water and Ocean Topography (SWOT) mission, significantly extending previous estimates derived from lower-resolution altimetry products. We apply an eddy-detection algorithm directly to the native 2 km SWOT swaths, without gridding or assimilation, and validate the detections against in situ measurements from shipboard current profiler data from one cruise in 2024, as well as against a statistically derived shipboard current-profiler-based eddy census. The comparison demonstrates good agreement in eddy size and intensity, confirming SWOT's ability to resolve high-latitude mesoscale structures previously undetectable or distorted in gridded altimetry. The SWOT-derived eddy census based on two full calendar years reveals a predominance of energetic anticyclones (Irminger Rings) in the basin interior and smaller cyclones along the continental slopes, with clear seasonal variability linked to boundary current instability. These findings provide the first observational benchmark for mesoscale activity in the Labrador Sea and illustrate SWOT’s potential to extend eddy statistics to high-latitude and ice-influenced regions, opening the way for a global assessment of mesoscale variability.