Abstract
A numerical ocean model is used to study the upwelling circulation off central Chile in response to local winds and remote forcing. In an idealized study of equatorial‐forced, intraseasonal variability (period of 50 days), a first mode coastal trapped wave (CTW) paddle is applied to the northern boundary with coastal sea level amplitude of 12 cm. Without this CTW forcing, the steady seasonal winds upwell undercurrent water from depths of 250–320 m to depths of 180–250 m. The subsequent formation of mesoscale and headland eddies drive this water into the Gulf of Arauco and to depths of 50–120 m. With the CTW paddle, the circulation is strongly modified. The mesoscale and headland eddies reform during the CTW upwelling phase. During the CTW upwelling phase, the upwelling over winds and eddies is enhanced by up to 40 m on the shelf. Model simulations are undertaken using realistic winds and a CTW paddle modulated by observed sea level. Without CTW forcing included in the model the agreement with data is poor. In the Gulf of Arauco area the variability of alongshore currents below 130 m is dominated by CTW activity. Above 130 m, wind‐driven current variability dominates. In agreement with the idealized CTW analysis, water is found to be upwelled from depths of 320 m to 100 m or less, and 10°C undercurrent water is found at the surface and within the Gulf.
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