Primary production associated with the Florida Current along the East Florida Shelf: Weekly to seasonal variability from mesoscale-resolution biophysical simulations

Numerical simulations with a mesoscale-resolution, three-dimensional coastal ocean model, coupled to a four-component ecosystem model, provide estimates of the frequency, intensity, duration, and property transport of upwelling events along the East Florida Shelf (EFS), and help identify their underlying mechanisms. The results compare favorably with in situ observations and demonstrate the strong variability in the ecosystem response associated with shelfbreak upwelling on daily to seasonal timescales. Monthly-to-seasonal nitrate inputs are mainly due to bottom Ekman transport, as the Florida Current (FC) jet interacts with the EFS topography, and summer coastal upwelling-favorable winds. The mesoscale variability in nitrate inputs along the EFS shelfbreak is directly related to Florida Current Frontal Eddies (FCFE), but their contribution to primary production is strongly modulated by the monthly-to-seasonal fluctuations in biological activity. Owing to short-lived biological activity and only approximately weekly recurrence periods, cumulative mesoscale contributions to primary production over the year are approximately 50% smaller than cumulative monthly-to-seasonal contributions. Since mesoscale contributions to net cross-stream transport are offshore and of equal or larger magnitude than monthly-to-seasonal contributions, FCFE activity should contribute significantly to the export of nitrate and phytoplankton from the continental shelf, especially north of 29 degrees N as the FCFEs intensify while translating poleward along the EFS. In conclusion, the coupled physical-biological simulations provide a new framework to investigate the ecosystem response to the FC circulation over the EFS and represent a necessary step toward the implementation of more elaborate ecosystem models for future ecological forecasting efforts in the region.