Figure 1. Site map of first and second priority California margin drill sites to be drilled on ODP Leg 167. The site locations are superimposed on 5-min topography of the west coast of North America.
Figure 2. Schematic representation of major oscillations of temperature-sensitive planktonic foraminiferal biofacies within the California Current system and related Alaskan Current Gyre during the later Miocene through Pleistocene interval, from Ingle (1973).
Figure 3. Surface atmospheric pressure, winter and summer, from Huyer (1983) compared to seasonal changes in northeast Pacific surface currents (Defense Mapping Agency, 1989). Surface winds will approximately parallel atmospheric pressure gradients. Note that seasonal variation in current patterns is driven by northeastern Pacific winds. Note also how the high and low pressure associated with the Asian monsoon helps to strengthen northeastern Pacific wind patterns in both summer and winter.
Figure 4. Illustration of strong interannual variation in California Current transport, from the CalCOFI data set (from Roessler and Chelton, 1987). Cold years (1949, 1950, 1954, and 1962) are typified by strong equator-ward transport of subarctic (low salinity) water. Warm years (1958, 1959) are typified by weak quatorward transport. Most of the interannual variation is coupled to ENSO events in the equatorial Pacific (Pares-Sierra and O'Brien, 1989).
Figure 5. Modern deep-water flow paths in the Pacific Ocean, based upon bottom potential temperature (Gordon and Gerard, 1970). Young bottom waters are directed toward the Leg 167 region.
Figure 6. Seasonal wind stress along the California margin from ship reports in the period 1854-1972 (from Huyer, 1983). Darkest shading marks wind stress >1.5 dynes/cm2, whereas intermediate and light shading represents 1.0-1.5, and 0.5-1.0, respectively. Upwelling wind stress (southward vectors parallel to the California margin) varies tremendously by season. Just north of the Leg 167 region at about 45°N, there is little seasonal upwelling; instead, there are short upwelling events. The northern end of the Leg 167 region exhibits the highest seasonality because of movements of the northeast Pacific high.
Figure 7. Offshore Ekman transport computed from long-term mean wind stress data for one-degree squares adjacent to the coast, for January, April, July, and September (from Huyer, 1983). Bars indicate the along shore extent of major upwelling studies.