The Occurrence, Variability, and Potential Drivers of Submesoscale Eddies in the Southern California Bight Based on a Decade of High‐Frequency Radar Observations

Abstract

AbstractSubmesoscale eddies form an important component of the circulation of the Southern California Bight (SCB). Despite their acknowledged significance in influencing ocean physics, biology, and ecological processes, submesoscale eddies have been exceptionally hard to study and observe because of the technical challenges posed by both field and remote platforms. Here, using a decade of high‐frequency radar surface current observations, we describe submesoscale eddies in the SCB. Between 2012 and 2021, a total of ∼235,000 eddies were detected, averaging 452 ± 116 eddies per week. Recurring eddies in certain locations over time, formed hotspots of eddy activity, largely in association with topographical features. On seasonal scales, eddies were more numerous in the summer and early fall. At inter‐annual scales, eddy counts increased by 40% in association with the 2014–2015 marine heatwave and the 2015–2016 El Niño. A domain‐wide diurnal cycle was observed in the formation of eddies and the normalized vorticity. To determine the relative contributions of tides and diurnal winds, an analysis of spectral components and their spatial distribution along the SCB was conducted. The results revealed that while diurnal tides may exert some influence on the diurnal variations, their effect is comparatively minor when compared to diurnal winds. This conclusion was reached by considering the prevalence of the S1 frequency, which is a meteorological tide known to be associated with motions induced by sea‐land breeze. Overall, diurnal variability was more prominent in the southern SCB and less significant toward the north.