electric potential measurements 



The possibility of measuring tidally generated 

 potentials in bays and through ocean channels has 

 been considered and discussed by numerous investi- 

 gators/'" The method has been employed in the 

 study of mass water transport between Key West and 

 Havana, and the average mass transport of the 

 Florida Current for the period of August 1952 to 

 August 1954 has been reported by Wertheim.^'' 



Electric potentials were initially measured in the 

 Bering Strait in 1949.*^ Continuation of these studies 

 in 1951-1952 yielded only sketchy results, primarily 

 because of installation problems associated with 

 maintaining electrode-cable systems in an area sub- 

 ject to ocean freezing and ice movement. 



Obviously, the most desirable procedure for 

 measuring potentials and for studying their relation 

 to water transport involves installation of electrodes 

 on opposite banks of a channel. Since this technique 

 cannot be followed in the Bering Strait, electrodes 

 were bottom-laid, perpendicular to flow, near the 

 eastern side of the Strait and connected to shore 

 recording equipment by appropriate signal links 

 (fig. 6). (A complete description of electrode systems 



and electrode construction has been given in refer- 

 ence 1 .) Edge effects of potential gradients extending 

 inland have been recorded using land electrode 

 systems laid perpendicular and parallel to flow. 



Young, Gerrard, and Jevons^ considered the 

 effect of potential gradients on a set of moored elec- 

 trodes near one shore of a broad channel and 

 demonstrated that the potential gradient ei where vi 

 is the observed velocity in the experimental area 

 exhibits the following relation (sea bottom-conduct- 

 ing): 



ei = — Vvi s -j- Csp (electromagnetic units) 



where 



V = earth's vertical field (gauss) 

 Vi = water velocity (cm/sec) 

 s = length of water filament (cm) 

 C = current density (abamperes/cm-) 

 p = specific resistance of the water (ohms/cm) 



Theoretically, C may have a value as great as 

 Vvo/p where Vo equals the mean velocity across the 

 entire channel and the conductivity of the earth bed 

 is negligible compared to the water. In such an 

 idealized case 



ei = — Vvi s + Vvo s 



SHORE ELECTRODES 



7500 FEET PERPENDICULAR, LAND SYSTEM 



INLAND ELECTRODE! 



CAA RANGE TOWERS 



SHORE ELECTRODES 



FIELD STATION 



,^,„ SEA ELECTRODE 

 RESTRICTED ^^, 



ANCHORAGE 3100 FEET,' 



AREA JEA^SYSTJM \ ^^^^^ ^,^^^^5 



Figure 6. 

 systems. 



Schematic of land and 



CAPE PRINCE OF WALES 



