UC San Diego

Southern California is part of an eastern boundary upwelling system (EBUS). This region is ecologically productive and socioeconomically significant, and how EBUS will respond to future changes in climate is of scientific and societal interest. Long-term monitoring is a key component for assessing how EBUS will be impacted by climate change and long timeseries of mooring observations are the focus of this dissertation.

Anomalous poleward flow was observed in southern California prior to and during the 2014 marine heatwave and 2015 – 2016 El Niño. Prior to the El Niño, local forcing drove a strengthened wind stress curl and a more persistent Southern California Eddy (SCE). The poleward recirculation of the SCE into the Southern California Bight (SCB) brought more waters from the California Current and North Pacific Subtropical Gyre closer to the coast. During the 2015 – 2016 El Niño, remote forcing drove persistent elevated coastal sea levels which forced poleward geostrophic flows and advected tropical waters into the SCB.

A volume budget was performed for southern California and this motivated developing an upwelling index. The upwelling index includes cross-shore geostrophic transport by using sea level changes right at the coast, accounting for coastal processes such as coastally trapped waves. Low-frequency upwelling anomalies indicate decreased vertical transport during the 2014 – 2016 upwelling seasons concurrent with the large-scale climate phenomenon in these years. This upwelling index is a practical tool for analyzing upwelling requiring minimal in-situ observations.

The upwelling forcing is valuable for assessing the physical impact on the coastal ocean, but it may not represent the oceanic response to upwelling. Multiple physical and biogeochemical properties are used to examine the coastal oceanic response to upwelling alongside the upwelling forcing. Event statistics are calculated using the long record of in-situ measurements, in addition to investigating the low-frequency in-situ anomalies. EBUS are susceptible to harmful algal blooms and a particularly pronounced red tide is examined alongside the physical processes that supported the red tide.