LAUSR

Abstract Mesoscale eddies exist throughout the global ocean and significantly impact local vertical marine stratification through the physical processes of stirring and pumping. While the vertical transportation dynamics of eddies are known, the contribution to the displacement of pycnocline depth from eddies has not been comprehensively investigated. In this study, the 17-year Argo dataset and satellite altimetry data are used to estimate the deepening and uplifting of the pycnocline depth induced by anticyclonic eddies (AE) and cyclonic eddies (CE), respectively. Pycnocline displacements exhibit multiple geographic and seasonal trends, with the largest magnitude occurring in spring. More pronounced displacements are concentrated in mid-latitudes, particularly along the western boundary currents, with peak displacements reaching more than 90 m. Furthermore, these displacements are positively correlated with eddy properties (particularly eddy amplitude), suggesting that higher intensity eddies may induce larger pycnocline displacements. In the eddy coordinate system, the pycnocline displacement reveals a monopole structure with a marked extremum in the eddy centre. At the eddy core, maximum deepening in AE reaches ~54 m in spring, but only ~25 m in autumn. In contrast, uplifting in CE reaches ~66 m (~18 m) in spring (autumn). The eddy-induced pycnocline displacements reported here emphasize the intrinsic vertical dynamics of eddies during oceanic observations and provide a pathway to reproduce the effects of eddies on variations of the pycnocline in ocean models.