ABSTRACT. We used a 21 yr time series of productivity for 6 seabird species nesting in large numbers at the Farallon Islands, 40 km offshore of San Francisco. California, USA, to assess proximate and remote factors leading to variation in the food supplies available to these predators. The latter sampled prey throughout a 3200 km2 area. Depending on foraging ecology and reproductive capacity, some specles were more sensitive to food web perturbation than others. A serious lack of food was indicated by negat.ivc reproductive anomalies during all warm-water events, some of which were classifled as tropical El Nifio and others which were not. Equally spectacular but positive anomalies occurred during years adjacent to the negative ones, particularly evident among the most sensitive species. Much of the annual variation, positive or negative, in seabird reproductive success was explained by variation in the Southern Oscillation and/or the Aleutian low pressure system, both of which affect sea-surface temperature and thermocline depth off California. Results indicate that perturbations in the marine food web of the Cal~fornia eastern boundary current system, as indicated by the availability of food to seab~rds, are much more complex than is generally appreciated, and are not conf~ned only to negative excursions from normalcy. ENSO is important, but other global atmosphere-ocean phenomena affect the California Current just as dramatically.
Remote forcing from the equatorial Pacific and local forcing from the North Pacific lead to interannual ocean temperature change along the west coast of the United States. In fall‐winter seasons, coherent temperature changes extending from the surface to 300 m depth indicate remote forcing. Correlations between time series of ocean temperature change and series of equatorial sea level pressure (SLP) at 12.4°S × 130.9°E were as great below 100 m as at the surface. From 1954 to 1986, coherent warming events occurred only during moderate to strong El Niño years. Warming events more closely related to local North Pacific SLP at 45°N × 165°W have correlations which were greatest at the ocean surface. The first three empirical orthogonal functions (EOFs) derived from ocean temperature change series at 0, 100, 200, and 300 m accounted for more than 98% of the variance. The first EOF is most closely correlated with remote forcing, and the second and third EOFs are closely correlated to local forcing. At the sea surface, lags of up to 6 months were found for remote forcing, while lags of less than 3 months were characteristic of local forcing. At 300 m there was an additional oceanic response which appears in phase with remote forcing. The study shows that interannual warming off the west coast has two distinguishable geographical origins and that the remotely generated warming signal arrives as complex dynamic structure having apparent propagation rates from 30 to greater than 200 km/d.
The magnitude‐7.1 Loma Prieta earthquake, which ruptured a segment of the San Andreas fault on October 17, 1989, and caused extensive damage over a large area of central California, also produced substantial motions in nearby Monterey Bay (Figure 1). Earthquake effects included a tsunami, or seismic sea wave, and subsequent surface water oscillations that were detected for about 24 hours following the main shock and widespread, substantial slumping of sediments on the Monterey Bay continental shelf and along the walls of Monterey Submarine Canyon.
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