moving across an infinite, elastic plate floating on an ideal liq.uid. For ice 

 over deep water, they used the following expression: 



To = 27r 



i^r (a) 



where Tg = natviral period (sec) 



/ = specific weight of ice (0.9 tons/m3)* 



h = thickness of ice (3m) 



g = gravity (9«83 ni/sec2) 



D = Eh 



E = Young's modulus for ice (3 x 105 tons/m^)* 

 fj. = Poisson's ratio (0.35) 



Using the above constants they obtained a value of Tg = 16 sec. Tak'ing 

 into account the depth of water at the observation point (150 to 200m) they 

 arrived at a value, Tq = 12 sec. According to their theory, a vertical load 

 moving over an infinite, elastic plate floating on an ideal liquid will gen- 

 erate not only waves of period Tq but will also produce "free" oscillations 

 or sweJJ. with period T„ where Tq < Tw < 00 . The oscillations of period Tq 

 are attenuated by cylindricsLL spreading, while those of T^ are primarily 

 attenuated in proportion to time. The waves with period T^, therefore, may 

 propagate over considerably greater distances than those of period Tq. Their 

 observations were in agreement with those predicted in theory; however, con- 

 siderably more observations would be necessary to rule out other modes of 

 wave generation. 



b. Purpose and Design of Experiment 



It clearly appears that oscillations recorded with seismographs and 

 gravimeters, as described in the literature, are vertical components of ordi- 

 nary gravity waves. Furthermore, correlation between wind speed and wave 

 amplitude exists but only above some threshold value. It is therefore inter- 

 esting to study more fully the nature of these waves, their directionsility 

 and mode of propagation, and the causes of their generation. For example, 

 are they associated with storm centers as are waves on the open ocean, and 

 is the moving load mechanism suggested by Sytinskiy and Tripol'nikov the 

 primary energy source? 



To answer these questions, a series of measurements of these waves 

 was begun in June 196I frcan drift station ARLIS II in the Arctic Ocean. A 

 LaCoste-Romberg undersea gravimeter, modified to record the vertical motion 

 of ice automatically on strip charts, was installed on the drift station. 

 Nearly continuous recordings of wave acceleration were made dioring the summer 

 of 1961. Simultaneously, a microbarograph sensitive to micropressure varia- 

 tions between 6- second and 6-minute periods was placed in operation at the 

 same location. Its output was also recorded on strip charts. In this manner. 



*The units of Sytinskiy and Tripol'nikov 



