A Large-Scale Seasonal Modeling Study of the California Current System

Abstract

A high-resolution, multi-level, primitive equation ocean model has been used to investigate the combined role of seasonal wind forcing, seasonal thermohaline gradients, and coastline irregularities on the formation of currents, meanders, eddies, and filaments in the entire California Current System (CCS) region, from Baja to the Washington-Canada border. Additional objectives are to further characterize the meandering jet south of Cape Blanco and the seasonal variability off Baja. Model results show the following: All of the major currents of the CCS (i.e., the California Current, the California Undercurrent, the Davidson Current, the Southern California Countercurrent, and the Southern California Eddy) as well as filaments, meanders and eddies are generated. The results are consistent with the generation of eddies from instabilities of the southward current and northward undercurrent via barotropic and baroclinic instability processes. The meandering southward jet, which divides coastally-influenced water from water of offshore origin, is a continuous feature in the CCS, and covers an alongshore distance of over 2000 km from south of Cape Blanco to Baja. Off Baja, the southward jet strengthens (weakens) during spring and summer (fall and winter). The area off southern Baja is a highly dynamic environment for meanders, filaments, and eddies, while the region off Point Eugenia, which represents the largest coastline perturbation along the Baja peninsula, is shown to be a persistent cyclonic eddy generation region.

A central California coastal ocean modeling study: 1. Forward model and the influence of realistic versus climatological forcing

“…We concentrate on this type of forcing comparison, time‐dependent, high‐resolution forcing versus climatology, mainly because previous regional model investigations of the CCS [e.g., Marchesiello et al , 2003; Batteen et al , 2003; Batteen , 1997] adopt climatological forcing for both the surface and lateral boundary conditions. Our focus here is on the impact that realistic atmospheric forcing has on the annual cycle of the CCS.…”

Phytoplankton scales of variability in the California Current System: 2. Latitudinal variability

“…In the CCS, the role of topographic features in perturbing the southward‐flowing coastal jet and promoting mesoscale meanders and eddies has been frequently studied in modeled and satellite SST and altimetric data [ Ikeda and Emery , 1984a, 1984b; Haidvogel et al , 1991; Batteen , 1997; Barth et al , 2000; Batteen et al , 2003; Marchesiello et al , 2003; Castelao and Barth , 2005]. It remains unclear the extent to which the meanders in the coastal jet are caused by the physical presence of the capes themselves, or by inherent baroclinic or barotropic instabilities in the flow.…”

“…From Washington to Point Conception (∼34°N–48°N) the coastline is aligned almost north‐south but several capes protrude from the coast, deflecting the jet offshore. The flow‐topography interaction results in increased mesoscale variability in the vicinity of the capes [e.g., Ikeda and Emery , 1984a; Haidvogel et al , 1991; Batteen et al , 2003; Marchesiello et al , 2003; Castelao and Barth , 2005] and enhanced biomass in the lee of the capes has also been observed [ Barth et al , 2005; Huyer et al , 2005].…”

Eddy properties in the California Current System

“…The last bin also includes all values higher than the upper limit of that bin. region with the highest eddy occurrence is seen near the coast, to the north of 40°N at the surface, which is associated with the mesoscale eddies forming due to the offshore separation of the CC at the surface [Batteen et al, 2003]. Westward propagation of these eddies contributes to the elevated eddy occurrence in the offshore region, to the north of 38°N.…”