Estimating Submesoscale‐Driven Particulate Organic Carbon Flux From Remote Sensing at a Dynamic Upwelling Front

Abstract

Submesoscale (1–10 km) vertical velocities at fronts enhance the exchange of particulate organic carbon (POC) and heat between the surface ocean and depth. While POC and temperature can be readily assessed in situ, direct quantification of flux remains uncertain due to the observational challenges of measuring submesoscale vertical velocities in the upper ocean. Here, we provided novel estimates of submesoscale‐driven POC flux by pairing airborne‐derived vertical velocities (NASA DopplerScatt) with POC estimates from satellite ocean color (Sentinel‐3 OLCI) in a persistent upwelling frontal structure in the central California Current System. Instantaneous, advective fluxes of POC and heat reached up to (1,000 mg C ) and (1,000 W ) at the front, both upward and downward. When integrated over sufficient spatiotemporal scales to achieve a negligible total volume flux, the turbulent flux, or net flux, can be estimated. Submesoscale vertical velocities made significant contributions to net downward POC flux ( mg C ) and upward heat flux ( W ). Spatial distributions of instantaneous fluxes, surface kinematics, and ship‐based, high‐resolution bio‐optical and hydrographic profiles indicated that POC flux below the mixed layer was driven by frontal overturning and filament subduction. This study contributes to the understanding of how submesoscale processes modify carbon export in the highly productive California Current System. This method can be expanded to other regions to further understand the influence of submesoscale‐driven flux on the marine carbon cycle.