Ocean mesoscale coherent structures dominate the generation of global submesoscale eddies

Ocean submesoscale eddies, characterized by horizontal scales less than the first baroclinic Rossby radius of deformation, are increasingly recognized for their critical roles in marine ecosystems, ocean energy balance, and the Earth’s climate system. Despite extensive research on these submesoscale features through high-resolution simulations and regional observations, our knowledge of their dominant driving mechanism from a global perspective is very limited. Here, we present the global observational evidence for the primary role of mesoscale Lagrangian coherent structures (LCSs) in driving submesoscale eddy generation by synergic application of high-resolution spaceborne synthetic aperture radar data and radar altimeter data. Applying a deep-learning detection system to more than three million global Sentinel-1 and Envisat SAR images, we found that more than 80% of detected submesoscale eddies are clustered within a 10-km range around mesoscale LCSs characterized by high kinetic energy and persistent straining. Further composition analysis quantifies that more than half of submesoscale eddies occur within the ring-shaped areas of coherent mesoscale eddies, where the strong strain is conducive to frontogenesis. Our findings highlight that the generation of submesoscale eddies is attributed to instabilities initiated by strain-induced frontogenesis. This study establishes a new paradigm for locating submesoscales by targeting LCSs, thereby supporting a global evaluation of their contributions to energy balance and material transport.