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



the normal-mode theory of shallow-water propagation. There is a 

 close analogy between propagation in shallow water and propagation 

 to long ranges in deep water of the central Arctic Ocean. In the 

 central Arctic Ocean, the dispersion is different from that in 

 shallow water because the Arctic propagation is controlled by the 

 velocity structure in the water; but the methods of analyzing the 

 Arctic signals parallels closely the methods employed by these early 

 workers . 



For many applications, it is convenient to consider the propaga- 

 tion in terms of ray theory. The connection between ray and normal- 

 mode theory is conveniently done in terms of the WKB approximation 

 (Kutschale, 1971). In other words, we sometimes deal with modes, 

 sometimes with ray theory, and we connect these two methods using the 

 WKB approximation. 



This paper is divided into two parts. The first part deals with 

 the character and analysis of Arctic SOFAR signals. The second part 

 deals with propagation loss as a function of range : measurements , 

 computations, and methods of estimating loss as a function of range 

 employing data from airborne measurements of surface ice roughness . 

 The band of frequencies of interest is from 2 to 350 Hz. The emphasis 

 is on a comparison of measurements made over deep water with theory 

 to arrive at an understanding of the causes of strong variations of 

 signal amplitudes and propagation loss dependent upon source and 

 detector depth, ice roughness, and bathymetry. 



The measurements span nearly a 17-year period beginning in 1958 

 with the first experiments initiated at NUSC on long-range explosive 

 sound transmission between floating ice stations. From these early 

 experiments, many of the unique features of the Arctic signals were 

 explained by Hecht (1960, 1961) , Kutschale (1961) , Marsh and Mellen 



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