BUCK: ARCTIC ENVIRONMENTAL LF ACOUSTICS MEASUREMENTS, 

 MODELS AND PLANS 



deep ray arrivals and, to the right, the later-arriving shallow rays 

 which are geometrically dispersed. This ability to distinguish the 

 two groups of rays for separate energy analyses enables some 

 interesting propagation studies that will be explained later. As 

 a generalization, very low-frequency energy is split about equally 

 between the two groups, which leads to a convenient definition of 

 "Arctic Deep Water." 



Figure 2 defines the geographic area to be covered in this paper. 

 The 500-meter basin is almost completely ice^covered all year 

 except for the ice limit shown in the neck of the Greenland Sea. 

 Therefore, "Arctic Deep Water" is deeper than 500 meters and is 

 ice covered. 



A few more definitions are useful: "Central Arctic Shallow 

 Water" is that area shown here that is shallower than 500 meters. 

 "Marginal Ice Zones" are those areas where the ice pack edge, which 

 can be quite diffuse, meets open water. This can be deep, as in 

 the Atlantic side, or shallow, as in the rest. The "Canadian 

 Archipelago Arctic" is generally locked-in, shore-fast ice. All 

 of these areas are considerably different acoustically. This paper 

 concerns only "Arctic Deep Water," although by omission it does not 

 imply any less interest or activity in those other areas. 



The remainder of this paper consists of some general observa- 

 tions on Arctic deep water acoustics, specific propagation results, 

 ambient noise data, signal-to-noise analyses, and, finally, a brief 

 description of future work. 



Some think of the Arctic as a quiet ocean — it is, and it 

 isn't. It is reputed to have low transmission loss — it does and 

 it doesn't. Figure 3 is a sample comparison of Arctic and open 



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