LOCAL SURFACE WIND DIRECTION (DEGREES TRUE) 



FIGURE 23 Significant coherences from figure 22 plotted ogoinst average surface wind direction observed 

 during the recording interval. 



b. Energy Transfer Considerations 



Sections h and 6a above indicate that the waves are generated in 

 a storm area and are selectively reinforced by micropressure waves acting 

 through the ice along the path of the ocean waves. It woiold be interesting, 

 therefore, to determine the relationship of micropressure wave force to the 

 force required to bend the ice and generate ocean waves. 



It should be shown first that the ice will indeed behave elastically 

 for the ice thicknesses and wave periods and amplitudes involved. Following 

 Robin (1963), a rough calculation can be made of the stresses involved in 

 bending an ice plate of thickness h into the form expressed by: 



y = A sin (27r -^) 



(18) 



If elastic bending occurs about a neutral plane in the center of the 



plate, the surface stress cr is given by 



(T _ Mh 

 xs - ^ 



where M is the bending moment at any point, and 1=/ y dy 



^.l/2h 



(19) 



Since M = 



EI 



d^^y 



(1 - p.'') dx'^ 



(20) 



where E = Young's modulus, and fj. = Poisson's ratio, an expression for 

 can be made by ccanbining equations (18), (19)* and (20) so that 



(^ 2n 2 



(1 - /^ ) 



^ A i^ sin {2-rr^^) 



(21) 



36 



