CIRCULATION NEAR THE WASHINGTON COAST 589 



The processes of mixing in the wake stream have not yet been 

 examined. However, there is some interest attached to the abrupt 

 change in salinity gradient seaward of the 31.0°/oo isosal. In essentially 

 all of the area between this and the next isosal, the surface salinities 

 are greater than 31.5°/oo and mostly greater than SLY^/oo- 



The dynamic topographies within 300 miles of the coast have been 

 quite consistent in all the cruises analyzed. Since only Cruise No. 7 in 

 July 1952, went as far offshore as 600 miles, data from this cruise are 

 combined with a composite of all the others to obtain a generalized 

 diagram for the area which is presented as Figure 8. The curves south 

 of 46°-30' are based principally upon data from Cruise No. 9 in early 

 September 1952. 



Appearing generally in all cruises are the lower dynamic heights 

 to the west of about 130°W, corresponding to northerly or northeasterly 

 flows of 5 cm/sec or less. Some changes in gradient occur in different 

 months but the general picture is little altered except that the contours 

 seem to tend more nearly northward in the early summer, as would be 

 expected from the meteorological conditions. Also appearing in all the 

 data is evidence for a deflection southward of northeasterly flowing 

 streamlines in the area between 128° and 130°Wand 47° to49°-30'N. 

 The data of Cruise No. 9 indicate that this flow continues southward 

 along the Washington Coast and is probably responsible for carrying the 

 Columbia River water southward. These results are consistent with 

 those of Doe (1952). 



G.E.K. Results and Time Studies 

 Early in the investigations, it was discovered that apparent cur- 

 rents measured hourly by means of the G.E.K. along a cruise track 

 showed continual changes in direction and magnitude, suggesting the 

 rotary changes of tidal period observed at lightships. These currents 

 typically had peak values of 15-20 cm/sec and occasionally as high as 

 35 cm/sec, the correction factor "K" for the G.E.K. being taken as 

 unity. To be contrasted with these are the velocities below 5 cm/sec, 

 determined from the dynamic heights. Tidal periods could be found 

 in the data by harmonic analysis, but the amplitudes were only about 

 one-fifth as great as the observed peaks. Later it was discovered that 

 inertial periods were present, with amplitudes of the same magnitude 

 or somewhat greater than those of tidal period. The inertial period 

 in this area is approximately 16 hours. The harmonic analyses of these 

 data were interpreted with some reservations due to the fact that the 

 ship was rapidly changing position and to the evident existence of ap- 

 parently random fluctuations of considerable magnitude. 



