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We present a modeling study of the upwelling ocean circulation off central Chile (34°–40°S). Using a primitive equation model, we make a numerical simulation of the ocean circulation for summer of 1993, a year characterized by moderate but persistent equatorward winds. The results indicate the formation of an eastern boundary current system that shows classical Ekman and geostrophic dynamics. A strong equatorward coastal jet develops during intense upwelling activity, induced by the prevailing equatorward winds. The spatial and temporal variability of the upwelling-favorable winds strongly controls the variability in the oceanic circulation. Upwelling activity in the coastal areas occurs during periods of growth, peak, and decay. The circulation in the region is divided into two distinct dynamical areas that extend north and south of a prominent cape (Punta Lavapie), located in the center of the model domain. During the peak upwelling stage, the equatorward jet separates from the coast at Punta Lavapie and remains separated in the northern region. This detachment is followed by the formation of cyclonic eddies and decreased upwelling during periods of wind relaxation. The northern area is affected by advection processes and weaker local winds. In contrast, the equatorward flows in the southern region are persistently attached to the coastline and are more coherent with the stronger local winds.

[1] In this article we analyze the momentum and vorticity balances of a numerical simulation of the upwelling circulation off central Chile (34� –40� S) and its response to interannual local wind changes. Our analysis indicates that the path of the upwelling jet is strongly controlled by the bottom topography. This topographic steering causes the jet to separate from the coast at the Punta Lavapie cape (� 37� S). Although the zeroth-order momentum balance is dominated by the geostrophic terms, the circulation is also affected by nonlinear processes, which lead to the formation of large meanders and the shedding of cyclonic eddies north of Punta Lavapie during periods of wind relaxation. The relative contributions of the zeroth-order vorticity balance and the advective terms are also strongly controlled by changes in the coastline geometry and the bottom topography. Vorticity is created along the current axes and transported toward the coast and the Peru-Chile Trench, where it dissipates. South of Punta Lavapie the across-shelf transports are weaker with equatorward flows that are more stable than in the north. Additional numerical simulations