661 / 2024-09-18 20:45:35

Quadruple Enhancement of Surface Chlorophyll Growth by Submesocale Fronts of Oceanic Eddies

Oceanic submesoscale processes,submesoscale fronts,ocean biogeochemistry,chlorophyll growth

Submesoscale fronts have been recognized as important contributors to nutrient supply for primary production in the euphotic layer. Their small spatio-temporal scale (10⁰-10¹ km, 10⁰-10¹ days) has hindered the understanding of their spatial structures, temporal evolution and biogeochemical impact. Here, by combining the global multi-platformed observations, we find that the submesoscale fronts around oceanic eddies are featured by an along-front enhancement of ageostrophic kinetic energy. Stronger fronts increase fourfold the surface chlorophyll growth rate on the warm side of the fronts, where the upwelling branch of a vertical secondary circulation emerges. The temporal evolution of submesoscale fronts of oceanic eddies is characterized by a frontal intensity peak with a lifecycle about 10 days. The frontal processes induce biogeochemical impact on a larger scale, which exhibits a net enhancement of surface chlorophyll of the corresponding eddies during this lifecycle, and the strongest enhancement of surface chlorophyll emerges when the frontal intensity reaches its maximum.