Role of Eddies in Primary Production in the California Current System

Mesoscale-induced processes such as eddies, fronts, and filaments are believed to play a key role in regulating nutrient transport and primary production in the California Current System (CCS), though their precise influence remains debated. Using satellite and model results, we show a weak negative correlation between surface eddy kinetic energy (EKE) and chlorophyll concentration nearshore, and a significant positive correlation offshore. EKE-based composite analysis of phytoplankton carbon and nitrate $\left(N{O}_3\right)$ budgets highlights the spatial variability of eddy impacts. In the nearshore band (0–100 km), eddy-induced horizontal advection reduces $N{O}_3$ and biological production. In the 100–300 km band, eddy-induced horizontal advection and vertical mixing increase $N{O}_3$ in the surface mixed layer, boosting local productivity. Beyond 300 km, horizontal eddy advection directly exports phytoplankton offshore, increasing its local concentrations. These results clarify how mesoscale processes modulate primary production across different regions of the CCS and offer critical insight into potential ecosystem responses to future climate change.