TIDAL DATUM PLANES 155) 
Vane feb Mapua Ape May) June. uly. Aug. sept) 5 Octa Nov. aDec: 
Feet 
Cedar Keys 
Pensacola 
Port Isabel 
Fic. 27.Annual variation in sea level, Gulf coast. 
Alaska.—For the Pacific coast of Alaska, observations for four years or more are 
available at six stations for which the curves of annual variation in sea level may be 
derived, stretching from Ketchikan in southeast Alaska to Adak Island in the Aleutians. 
The curves for these stations are shown in Figure 29. The years of observations for 
each of these stations are indicated on the diagrams. 
In general sea level all along this stretch is high in the late fall and early winter 
months and low in the summer months, except at Skagway which shows a secondary 
