114 



Water 



mixed layer may also be thick where winds 

 have caused it to pile up against coastal 

 points (Fig. 101), and it may be thin or ab- 

 sent where winds have swept it away from 

 the leeward side of the same points. As a 

 result, the difference in temperature on op- 

 posite sides of points may be as much as 

 10°C, as pointed out long ago by McEwen 



(1916) and confirmed in many unpublished 

 measurements by C. L. Hubbs. This differ- 

 ence is sufficient to produce differences in 

 species and abundance of fishes, mollusks, 

 crabs, algae, and probably many other or- 

 ganisms, which in turn may be reflected in 

 the types of sediment present on opposite 

 sides of points, as shown for a bay of Baja 



I i 8°30' 



II8°30' 



Figure 101. Typical surface 

 temperatures, depths to 12.8°C 

 surface, and probable paths of 

 drift cards for summer and 

 winter in Santa Monica Bay. 

 Surface temperature during the 

 July 6, 1955, cruise was highest 

 at the windward side of the 

 point that forms the southern 

 limit of the bay; surface tem- 

 peratures during the February 

 22, 1956, cruise were nearly 

 uniform at about 13° C. Depth 

 to the 12.8°C isothermal sur- 

 face is given for both cruises, 

 with an interpretation of cur- 

 rent direction for the winter 

 one. Estimated trajectories of 

 drift cards for winter and sum- 

 mer are given at the bottom, 

 with the shaded part of the 

 circles showing the percentage 

 recovery of the 14 to 50 drift 

 cards released at each station. 

 Compiled from charts and data 

 of Stevenson, Tibby, and Gor- 

 sline (1956). 



