The temperature profile along lat. 47° N. 

 (fig. 7c) contains none of the striking features 

 of the two meridional sections. Although a 

 temperature minimum existed at 100 to 150 

 meters, minimum temperatures exceeded 5° C. 

 and are believed to be chiefly the result of 

 winter-cooling rather than the result of ad- 

 vection from the temperature-minimum 

 stratum shown in the previous two profiled. 



The isotherms slope gradually downward to 

 the east and dip sharply near the coast re- 

 flecting the northward flow off the Washington 

 coast. 



Salinity 



The salinity is of particular interest as a 

 criterion for indicating the presence of vertical 

 divergence south of the Aleutian Islands and 

 defining the Subtropic boundary. 



Salinity profiles along long. 175° W., 155° W. 

 and lat. 47° N. (fig. 8) show the dilute surface 

 layer occurring from the surface to a depth 

 of 100 meters which is characteristic of the 

 Subarctic region. Tully and Barber (1960) have 

 discussed the causes of this dilution and com- 

 pared it with an estuarine system. As indicated 

 earlier in the discussion of sigma-t, the 

 salinity is a dominant factor in the stability 

 of the water column during the winter period 

 because of the relatively vertical isothermal 

 conditions, particularly north of lat. 45° N. 



No direct indication of vertical divergence, 

 which would transport high salinity water to 

 the surface, is evident in the salinity distribu- 

 tion along long. 175° W. (fig^ 8a). The sharpest 

 halocline found, however, during the entire 

 cruise occurred at this longitude between lat. 

 50° and 51° N. The moderate, horizontal 

 component of flow in the Alaskan Stream 

 probably prevents the very minor vertical 

 component from being manifest in the water 

 structure near the surface. There is evidence 

 in the temperature profile at this longitude 

 that a vertical movement was present at lat. 

 49°30' N., so one should not discount the 

 possibility that such a feature may have 

 existed farther to the westward where the flow 

 of the Alaskan Stream must be reduced by 

 divergences to the north through the passes 



and to the southward by water recirculating 

 in the eastern Subarctic region. 



Along long. 155° W. and lat. 47° N. (fig. 8) 

 salinities in the upper 100 meters were 

 relatively uniform with a range of 32.6 to 

 32.8 °/oo, except near the Washington coast 

 where further dilution occurred. Along long. 

 175° W. (fig. 8a), however, the salinities 

 ranged from 32.6 to 34.3 °/oo. Between lat. 45° 

 and 44° N. there was a sharp gradient near 

 the surface. Southward at lat. 43° N. a gyre 

 or possibly an intruded tongueof lower salinity 

 water interrupts the continuity of steadily 

 increasing values, but at approximately lat. 

 42° N. the almost vertical 34 °/oo isohaline 

 in the upper 200 meters denotes the position 

 of the Subtropic boundary. Rather than shifting 

 southward in winter in response to a south- 

 ward shift of the North Equatorial Current, 

 the boundary appears to occur a little farther 

 to the northward than it has in recent years 

 during summer. Below 200 meters the salinity 

 minimum stratum which is ever present south 

 of lat. 40° N. is clearly evident. 



Comparison with other available data as 

 far back as 1955 shows that the water structure 

 in the vicinity of the northern extent of the 

 salinity minimum and the position of the 

 surface boundary indicated by the upper 34 °/oo 

 isohaline have been relatively constant in the 

 northern, central Pacific during the past 6 

 years. This implies a dynamic equilibrium 

 condition between advection, diffusion, pre- 

 cipitation, and evaporation. 



Dissolved Oxygen 



Vertical profiles of dissolved oxygen are 

 shown in figure 9. 



No new information was obtained from the 

 oxygen values; nor was this entirely unexpected. 

 The main purpose of the observations was to 

 provide a supplementary parameter for water 

 mass analyses. 



In general, values in the surface layer were 

 at or near saturation. The low values 

 « .Img.at./l) at and below 200 meters depth, 

 between lat. 50° and 51° N. along long. 175° W. 

 and at lat. 52° N. along long, 155° W. are 



12 



