KUTSCHALE: LOW-FREQUENCY PROPAGATION IN THE ICE-COVERED ARCTIC OCEAN 



1970 with great care by Buck, Magnuson, and Chalfant (1970) between 

 several ice stations. They are the best measurements available under 

 carefully controlled conditions and serve as a good check on the 

 computer modeling. 



For the comparison at 20 Hz, and 0.2 dB per bounce were ass\imed 

 for reflection loss. Data at about 800 nautical miles fall along an 

 extension of the loss curve for 0.2 dB per bounce. The computations 

 will be extended to longer ranges, but 0.15 to 0.2 dB per bounce is con- 

 sistent with the airborne measurements for the area. The measurements 

 of Buck, Magnuson, and Chalfant show clearly the strong depth dependence 

 of loss for waves below about 70 Hz. Above 100 Hz, the depth 

 dependence is relatively weak. As an illustration, for a shot at 

 60 feet the loss of Figure 21 is nearly 10 dB higher than that shown 

 for the 400-foot shot. 



Attention will now be turned to the important question of pre- 

 dicting reliable estimates of propagation loss as a function of 

 range for given source and detector depths in deep water of the 

 central Arctic Ocean. 



The pioneering thrust in this area was made by O. I. Diachok 

 of the Naval Oceanographic Office. We have collaborated on extending 

 the work from the marginal sea ice zone to the central Arctic Ocean. 

 Later, an extensive series of experiments completed during May 1974 

 will be briefly described. 



The basic question is whether reliable estimates of propagation 

 loss as a function of range can be obtained from measurements of 

 surface ice roughness and computer modeling. Experiments strongly 

 suggest that this is the case. 



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