PETERSON and MILLER: SEASONAL CYCLE OF ZOOPLANKTON ABUNDANCE 



SCALES: THOUSANDS 

 OF WIND -KILOMETERS 



FIGURE 6.— Progressive vector diagrams for the wind at Newport, Oreg., for the winters of 1969-70, 1970-71, and 1971-72. 



three intervals with winds from the east: most of 

 October, 23 November to 8 December, and 30 De- 

 cember to 12 January. The entire 6-mo period of 

 winter winds lacked the southwesterly storms 

 that are characteristic of most winters. The other 

 two winter wind patterns shown in Figure 6 are 

 more typical on the basis of comparisons to the 

 winters of later years (1972-73, 1973-74, 1974- 

 75). 



Upwelling index data taken from Bakun (1973) 

 for the winters of our study are presented in Table 

 3. Negative values of the index indicate winds that 

 will produce shoreward convergence of surface 

 waters on the average over the month. Negative 

 values of the anomaly indicate greater-than-usual 

 shoreward convergence. Indices for winter 1969- 

 70 are quite different from those of the other two 

 winters. Onshore convergence was anomalously 

 high in 1969-70 and anomalously low in 1970-71 

 and 1971-72. 



The zooplankton data (see Peterson and Miller 

 (1976) for detailed tabulations) indicate that the 

 northward flow of the Davidson Current probably 

 was much greater in 1969-70 than in the other 

 two years. A number of southern zooplankton 

 species had their greatest abundance during that 



TABLE 3.— Monthly upwelling inde* values from Bakun (1973) 

 for midwinter period at lat. 45 °N, just north of the Newport, 

 Oreg., transect, during the years of our study. 



winter: Clausocalanus jobei, C.paululus, Oncaea 

 dentipes, and O. subtilis. All of the above 16 

 copepod species are indicators of water originating 

 south of at least Cape Mendocino, Calif. (Olsen 

 1949; Fleminger 1964, 1967; Frost and Fleminger 

 1968). 



The physical implication of this set of biological 

 observations is that winter periods of gentle winds 

 directly from the south (Figure 6a) are much more 

 effective at moving water northward alongshore 

 than winter periods of violent southwesterly 

 storms (Figures 6b, c), even though the total 

 northward component of the winds during the 

 stormy winters might be much greater. This is in 

 agreement with the temperature results (Figure 

 5) and with the anomaly in the upwelling indices. 



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