surfaces of constant density. The seaward limit 

 of the nearshore province is not often well defined 

 but appears to lie farther from the coast than its 

 upper-zone analogue (figs. 7, 8, and 9). This 

 displacement is presumed to occur because upward 

 deflection of coastward flow occurs farther offshore 

 with increasing depth in response to proximity 

 of the sloping sea floor. 



Coastal upweDing in the area is largely seasonal 

 and is caused principally by response of surface 

 waters to the spring shift in prevailing wind 

 direction from southwest to northwest (Lane, 

 1962). Because characteristics of the water in the 

 lower-zone nearshore province are affected by this 

 seasonal process, this province stands in contrast 

 to that of the offshore, where seasonal changes 

 are difficult to distinguish from nonseasonal 

 changes (Tully, Dodimead, and Tabata, 1960). 



Depth to which upwelling affects distribution of 

 heat, salt, mass, and oxygen concentration is pre- 

 sumed usually to be less than about 200 m. 

 (Sverdrup, 1938; Doe, 1955). Portions of many of 

 the vertical sections that lie within the nearshore 

 province, however, exhibit significant onshore as- 

 cension of isopleths of these variables at depths 

 in excess of 250 m. (figs. 7, 8, 9, and 10). 



Located beyond direct influence of bottom 

 topography and seasonal processes, the lower- 

 zone offshore province exhibits the horizontal uni- 

 formity of property distributions that is typical of 

 the lower-zone subarctic. Small slopes of surfaces 

 of constant salinity, temperature, and density 

 indicate sluggish circulation, except where deep 

 eddies occur. The recmrent nature of some of the 

 closed-curve patterns that suggest eddylike mo- 

 tion has been noted by Budinger et al. (1964). 

 That these patterns are recurrent implies that 

 they do not result from internal-wave distortion 

 of the mass field or from failure of the assumption 

 that measurements were synoptic — possibilities 

 suggested by Defant (1950). 



Currents 



H-21 H-2Z H-gj H-24 



The study area 

 region where the 

 feed the California 

 Alaska gyre systen 

 et al., 1963). Prev 

 study area (Doe, 

 1957) show weak, 

 that are sensitive 

 bottom topography 



512 



is largely shoreward of the 

 West-Wind Drift diverges to 



Current to the south and the 

 1 to the north (see Dodimead 

 ious works that included the 



1955; Barnes and Paquette, 



variable geostrophic currents 

 to the influence of wind and 



1961 



100 2 



4 



250 

 500 



1000 



1962 



1963 



1964 



Figure 10. — Vertical profiles of July oxygen concentration 

 along lat. 44° N. (approximately). Longitudinal relations 

 between profiles are preserved. Sea floor is stippled. Con- 

 tour interval is 0..5 ml./l. Depth scale is logarithmic. 



The reference level of 500 dbar. (decibars) is 

 used in the present work; this value was selected 

 because data were insufficient below the corre- 

 sponding geometric depth. Agreement in speed 

 and direction of geostrophic flow referred to the 

 500 dbar. surface with flow referred to 1,000 dbar., 

 previously accepted as adequate for direction 

 (Dodimead, 1961, and others), is suflScient to 

 warrant use of the 500 dbar. level. Dodimead et al. 

 (1963) presented flow at 500 dbar. with respect 

 to 1,000 dbar. for summers of 1955-59. Their 

 charts, wliicli include the study area, indicate 

 current speeds on the 500-dbar. surface that gen- 

 erally do not exceed 0.8 cm. sec."'; i.e., they are 

 insignificant. Also, average flow direction referred 

 to 1,000 dbar., and to 500 dbar. by the extension 



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