Three interacting freshwater plumes in the northern California Current System

The northern California Current System is impacted by two primary freshwater sources: the Strait of Juan de Fuca and the Columbia River. The Columbia is frequently bidirectional in summer, with branches both north and south of the river mouth simultaneously. We describe the interaction of these two warm Columbia plumes with each other and with the colder plume originating from the strait. The interactions occurred when a period of strong downwelling-favorable winds and high Columbia River discharge was followed by persistent and strong upwelling-favorable winds. The northward plume that developed under the downwelling winds extended over 200 km along the coast to the Strait of Juan de Fuca and into the strait. The plume subsequently wrapped around Juan de Fuca Strait water in the counterclockwise seasonal eddy just offshore of the strait. Inspection for similar wind and outflow conditions (> 0.15 N m(-2) and 10(4) m(3) s(-1), respectively) suggest that these events might have occurred in roughly half the years since 1994. Surface drifters deployed in the Columbia plume near its origin tracked this plume water northward along the coast, then reversed direction at the onset of upwelling-favorable winds, tracking plume water southward past the river mouth once again. Recent (similar to 1-2 day old) and Aged (> 14 day old) plume water folded around the newly emerging southwest tending Columbia plume, forming a distinctive sock shaped plume. This plume was a mixture of similar to 10% New (< 1 day old) water and similar to 90% Recent and Aged water from prior north tending plumes.