Assessment of global eddies from satellite data by a scale-selective eddy identification algorithm (SEIA)

Automatic ocean eddy identification algorithms are crucial for global eddy research. In this study, a scale-selective eddy identification algorithm (SEIA) that features improvements in the detection and tracking processes is presented for the global ocean based on sea level anomalies. First, the previous strategy of using thresholds to define eddy boundaries is replaced with a scale-selective scheme, which restricts the numbers of upper and lower grid points based on the data resolution and eddy spatial scale. Under such conditions, overestimated eddy boundaries will be flexibly removed. Furthermore, an effective overlap scheme is used to track eddies by calculating the intersection ratio of time-step-successive eddies. The SEIA generates approximately 1.6 million anticyclonic eddies and 1.5 million cyclonic eddies by the satellite altimetry product from the French Archiving, Validation, and Interpretation of Satellite Oceanographic Data (AVISO) over a 29-year period (1993-2021; https://doi.org/10.11922/sciencedb.o00035.00004). Assessments of the global distribution of eddies, eddy propagation speed, eddy path and evolution characteristics, and observation-based eddy hydrological conditions verify the validity of the SEIA. This study provides solid support for ocean eddy-related research in a warming climate.