The California current system—hypotheses and facts

摘要: The primary purpose of this paper is to describe the seasonal variation various currents which comprise California Current System—the Current, Undercurrent, Davidson and Southern Countercurrent—and investigate qualitatively dynamical relationships among these currents. Although majority information was derived from existing literature, previously unpublished data are introduced provide direct evidence for existence a jet-like Undercurrent over continental slope off Washington, illustrate ‘event’-scale fluctuations in during winter season. The literature thoroughly reviewed synthesized. In addition, more important, geostrophic velocities computed along several sections Columbia River Cape San Lazaro dynamic heights given by Wyllie (1966), Budinger, Coachman Barnes (1964), Reed Halpern (1976). From long-term monthly wind stress vertical component curl (denoted τ) Nelson (1977), interesting new conclusions made. 1. flow that has been denoted generally both an offshore nearshore maximum its alongshore coponent. 2. region strong appears be related at coast, τyN, all latitudes. Curl τ near coast may also contribute signal, accounting lead current about 40°N northward. Large-scale separation fall countercurrents headlands account sudden occurrence late summer appear as large anomalies wind-driven coastal south 40°N. 3. Mendocino southward northward mean imposed on distribution. largest where locally strongest, particular, Francisco Bight. It responsible portion occurs California, Eddy or Countercurrent. When weakens regions, dominates flow. Flow vicinity flows. There some periods τyN-driven inshore At latitudes, expected superimposed 4. spatial distribution oftthe τ. areas, τl, roughly phase with τy 180° out coast. Southward lags negative two four months. strongest early fall. annual location 250–350 km shore Washington Oregon, 430 Mendocino, 270 Point Conception 240 northern Baja. branch bends shoreward 30°N, consistent extension τ, so (25°N), single observed within 200 5. A third distances exceeding 500 6. known consists regions forcing dynamically different—seaward Oregon between Conception, positive τ; not but 7. continuous maintained parts winter. This separate northward-flowing Alaskan Currents time-dependent Vancouver Island. banded structure if 8. progression (hence τl) South seems Velocities depths have maxima, one indistinguishable, except location, undercurrent Oregon-Washington shelf.