Anomalous Southward Advection During 2002 in the Northern California Current: Evidence from Lagrangian Surface Drifters

[1] Equatorward velocities in the upwelling jet of the northern California Current were 0.05–0.06 m s−1 faster in spring and summer 2002 than on average over 1998–2002. This result is based on a five-year data set of surface drifters released across the continental margin off central Oregon (44.65°N) during April and July of each year. At this speed, anomalous water displacements of over a degree of latitude can occur in 20–25 days. Given a source of cold, Subarctic water to the north, this anomalous southward displacement is a plausible explanation for the cold, nutrient-rich halocline water observed off Oregon during the summer of 2002. This interannual variability in the northern California Current and its implications for the ecosystem response, i.e., increased primary productivity, may be contrasted with interannual variability of the opposite sign - increased poleward velocity, warmer temperatures and decreased productivity - observed in this same region during El Nino years.

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