Oregon and its connection to the California Current System

The coastal upwelling region near Cape Blanco, Oregon (433N) o! the west coast of the United States was studied using a towed CTD on SeaSoar, a shipboard acoustic Doppler current pro"ler (ADCP), satellite sea surface temperature maps and surface drifters during August 1995. The equatorward upwelling jet was inshore of the shelfbreak north of Cape Blanco, meandered gently o!shore around the Cape, and then veered sharply o!shore just to the south of the Cape. Analysis of vertical sections of density, velocity and `spicinessa con"rmed the separation of an upwelling jet and front; the jet was followed from over the shelfbreak north of the Cape to 100 km o!shore downstream of the Cape. The separating jet originates from the coastal upwelling jet leaving the shelf, but is augmented by an o!shore branching of the poleward undercurrent. By combining information from ADCP streamfunction maps with analysis of hydrographic data, including distributions of the tracer-like quantity `spicinessa, a conceptual model of the three-dimensional circulation near the Cape emerges. A mid-shelf upwelling jet encounters a coastal promontory then turns o!shore, stretching and deepening as it crosses the continental margin. The jet then turns back shoreward (cyclonically) where th