Global Sea Surface Cyclogeostrophic Currents Derived From Satellite Altimetry Data. Issue 1 (20th January 2023) - Cao, Yuhan
Abstract: Sea surface currents (SSC) derived from the sea surface height anomalies (SSHA) as measured by multi‐satellite altimeters are widely used for various applications including studies on ocean dynamics, marine ecology, and climate change. However, present SSC products estimated on the assumption of an idealized geostrophic balance is biased. To overcome this idealization, this study considers flow curvature in the estimation of sea surface velocities in the global ocean, with the computation scheme validated using numerical model results. It is demonstrated that the inclusion of curvature into SSC estimations significantly changes SSC dynamic features in terms of kinetic energy, enstrophy (the maximum spatial difference is about 15%), and strain rate (the maximum spatial difference is about 10%). Such correction is of importance to the application studies relying on the SSC products from the satellite measured SSHA. Plain Language Summary: Sea surface currents (SSC) are usually derived from satellite altimetry measurements based on the balance between the pressure gradient and Coriolis effect, that is, geostrophic approximation. In this study, it is presented for the first time that the effect of flow curvature is considered in the calculation of the SSC for the global ocean using the satellite remote sensing sea surface height anomalies. Such correction is significant in terms of eddy kinetic energy, enstrophies and strains. The results show that maximum spatial differences in eddy kinetic energy and enstrophy (15%) is significantly greater than the strain rate (10%). In addition, it is of great significance for cyclostrophic‐correcting the surface geostrophic velocities derived from altimeters in meandering, boundary currents and eddy‐rich regions. Key Points: An iterative method is used to cyclostrophic‐correct global sea surface velocities from Archiving, Validation and Interpolation of Satellite Oceanographic Data‐gridded altimetry The impact of curvature on the ocean currents can be seen in the dynamics of meandering, boundary currents and eddy‐rich regions Maximum spatial differences in eddy kinetic energy and enstrophy (15%) is significantly greater than the strain rate (10%)