between clockwise and counterclockwise at both first- and last-quarter 

 moons . 



From (3) and (4) above, in the Channel Islands area the higher 

 the tide, the faster the current speed. This point is further demonstrated 

 because the lower tides of the full moon, as compared to the new moon, 

 brought a correspondingly lower current speed. With increasing depth, 

 the current meters were influenced less by the tides. From the 

 upper current meter, data indicated that the current tended to rotate 

 through 360° in a constant clockwise direction, whereas data from 

 the lower current meter did not indicate a consistency in rotational 

 direction. This rotational pattern was more apparent during the 

 new and full moons when tidal activity was at a maximum. 



4. Dynamic Topography . Dynamic height anomalies were derived 

 and plotted primarily to supplement the results obtained by parachute 

 drogue and current meter observations. The method for determining 

 the reference level as outlined by Defant (1961) was used. In addition 

 to the normal and well known limitations of this type of current 

 analysis, three further variables for this survey are: (1) a study 

 of a small area is subject to greater error than a large area (Sverdrup 

 et al , 1942); (2) effects of the irregular coastline; and (3) varying 

 depths (Reid et al, 1958). Despite these limitations, agreement 

 with the parachute drogue results is exceptionally good. Using the 

 September Nansen cast data, the 0-, 50-, and 100-decibar surfaces 

 were contoured relative to the 500-decibar reference level (Fig. 27). 



FIGURE 27. TOPOGRAPHY OF THE 0-, 50-, AND 100-DECIBAR SURFACES 

 RELATIVE TO THE 500-DECIBAR SURFACE 



The topographies depict a general counterclockwise flow around 

 San Nicolas Basin with greater speeds at the periphery. Here, speeds 

 of approximately 32.5 cm/sec were indicated at the 0-decibar surface 

 which is in agreement with the 5-meter drogue released at site 3. 

 In the water over the basin, drogue speeds decreased with increasing 

 depth. Dynamic calculations also showed decreasing speeds with increasing 

 depth. 



28 



