Examining the sensitivity of surface chlorophyll to upwelling events of variable frequency in the California current system

Eastern Boundary Upwelling Systems (EBUS) spatially encompass approximately 1% of the ocean surface area, but are responsible for nearly 20% of global fisheries production. This significant biological production is primarily attributed to the nutrient-rich waters brought to the euphotic zone through a physical process called upwelling. In an attempt to understand the various physical and biological processes occurring on a wide range of temporal and spatial scales, the California Current System (CCS), one of the major EBUS, has been subject to a multitude of scientific studies over the past several decades. Recent modeling enhancements have enabled researchers to investigate mesoscale processes contributing to physical and biological variability within the CCS. This information could be used to improve our understanding of plankton dynamics and ultimately, be applied to higher trophic levels and coastal fisheries management.;The primary focus of this study was to investigate whether high-frequency (3 - 7 days) wind events generate a positive response in surface chlorophyll-a (chl-a) within regions of the CCS. The high-frequency wind events were hypothesized to be insufficient to generate enough upwelling and subsequent lift in the nutricline to produce a significant response in surface chl-a concentrations. Rather, I expected that low-frequency (7 - 30 days) upwelling-favorable wind events would raise the nutricline for a period long enough to sustain a phytoplankton bloom. Utilizing high-resolution climate model data, a frequency analysis was performed by conducting a correlation between chl-a concentrations and meridional wind stress (Tauy) events at lagged intervals. High-frequency Tauy events are found to have a minimal impact on chl-a concentrations throughout the CCS. At low frequencies, chl-a concentrations were shown to have a positive response to Tauy events within 100km of the CCS coastline. These results imply that high-frequency upwelling events have little to no immediate impact on the chl-a concentrations. However, the low-frequency Tauy events appear to persist long enough to generate a response in surface chl-a and positively impact productivity within the CCS.