Wind‐forced modeling studies of currents, meanders, and eddies in the California Current system

Abstract

Abstract. This process-oriented study of the California Current system (CCS) uses a high-resolution, multilevel, primitive equation ocean model on a/3 plane to isolate the response of that eastern boundary oceanic regime to temporal and spatially varying wind forcing. To study the generation, evolution, and maintenance of many of the observed features such as currents, meanders, and eddies in the CCS, the model is forced from rest with seasonal climatological winds. In response to the prevailing wind direction, surface equatorward currents develop, along with upwelling of cooler water along the coast and a poleward undercurrent. Baroclinic/barotropic instabilities in the equatorward surface current and poleward undercurrent result in the generation of meanders near the coast.As the meanders intensify, cold upwelling filaments develop along the coast and subsequently extend farther offshore. In time, the meanders form both cyclonic and anticyclonic eddies, which subsequently propagate farther offshore,, Longer. simulation

Process-oriented modeling studies of the 5500-km-long boundary flow off western and southern Australia

“…The generation of a poleward undercurrent along the west coast is consistent with previous process-oriented modeling studies which have shown that a poleward undercurrent can be generated due to meridional variability in the predominantly equatorward wind stress (Batteen et al, 1989) and/or to the planetary beta effect (e.g., McCreary et al, 1986;Batteen, 1997). The beta effect allows the existence of freely propagating planetary waves, i.e., Rossby waves (Gill, 1982).…”

A numerical study of the dynamics and energetics of cool filaments, jets, and eddies off the Iberian Peninsula

“…Note that the present diagnosis is somewhat different from the traditional energy diagnosis, as, for instance, applied recently by Batteen [1997] and others [Treguier, 1992;Ivchenko et al, 1997]. The present analysis concludes that horizontal (barotropic) and vertical (baroclinic) shear instabilities are unimportant throughout the whole simulation period, while the frontal instability and the mixed frontalconventional baroclinic instability are of equal importance, even during the growth phase.…”

“…However, in run B the effect of an irregular coastline is still present. As noted originally by Arthur [i965] and also observed by Batteen [1997], an alongshore variability in the linear wind-driven upwelling is to be expected when irregularities in the coastline geometry are introduced, even under uniform wind forcing. Thus the buildup of the upwelling front will exhibit an alongshore variability, which in turn will have an influence on the timing of the onset of instabilities.…”

“…It extends the work of McCreary et al [1991], in that it includes irregularities in the shelf-slope topography and coastline geometry and a nonlinear energy analysis is performed. It extends the work of Batteen [1997], in that a much finer resolution is employed and a different, and presumably more relevant, energy diagnostic scheme is employed. Finally, it extends the work of , in that a much finer resolution is employed providing a more realistic picture of the ensuing circulation in the shelf-slope region off the Iberian Peninsula, including the growth of significant cool filaments, eddies, and jets.…”

“…In contrast, both the shortwavelength, frontal instability and the longer mixed mode instability are resolved in the present experiment, and it is shown that the two baroclinic instabilities, namely, the frontal instability and the mixed frontal-conventional baroclinic instability, are actually the dominant ones, even during the quasi-equilibrium phase. Hence, although correct for their model response, the conclusion reached by Batteen [1997] is incomplete. The conclusion reached in the present analysis also appears to be in contrast to those of McCreary et al [ 1991] and Fukamachi et al [ 1995], who concluded that the frontal instability was the sole instability mechanism during the growth phase.…”