A numerical study of seasonal wind forcing effects on the California Current System

Abstract

A high-resolution, multi-level, primitive equation ocean model is used to examine the response of an idealized, flat-bottomed, eastern boundary oceanic regime on a beta-plane to both steady and seasonally-varying climatological wind forcing. The focus of the study is the California Current System along the coastal region, from 35 deg N to 45 deg N, off the Western United States. With steady equatorward wind forcing, a surface equatorward current and poleward undercurrent develop. Eddies form around days 60 and 7 with initial development in the northern region of the domain. The strong meandering current continues to grow throughout the 360 days of model time and can produce eddies that have wavelengths up to 200 km and can propagate at least -200 km offshore. When the alongshore component of the temporally averaged seasonally varying climatological wind forcing is used, there is a weak poleward undercurrent and equatorward surface current. There is weak upwelling and very little eddy activity with the eddies only propagating to -100 km offshore. When alongshore component of the time-dependent wind forcing with spatial variability in latitude is used, a surface equatorward jet, poleward undercurrent and eddies are generated. The eddies form throughout the domain in this experiment due to a competition between the 0-plan effect and the continuous and stronger equatorward wind forcing in the southern portion of the domain. The eddies in this experiment propagate at least -150 km from shore