Page 158 - GIS for Science, Volume 3 Preview

ARCTIC SOUNDSCAPE
Atlantic Deep Water Case, Summer, 63 Hz
Beaufort Deep water Case, Summer, 63 Hz
Beaufort Deep water Case, Summer, 63 Hz
A
The Arctic is a perfect example of the value of underwater acoustics in the
study of oceanography and the challenges and complexities of its application.
From an acoustics standpoint, the Arctic is a unique environment. Cold
water near the surface leads to lower sound speeds at the surface. The result 3 is a condition called surface ducting, which allows sound generated at the
surface, such as noise from ships and breaking ice, to propagate great distances. 4 1
The consequence is that a single ship in the Arctic can ensonify an entire basin,
whereas adding a single ship to the ocean in a different region might not even be 2 noticed.
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Range (km)
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Ocean temperature and sound speed along meridional transects in the Pacific and Atlantic Oceans with corresponding acoustic ray paths getting shallower at the poles.
Typical vertical slice acoustic transmission loss simulation in the mid-latitude Pacific Ocean (A) compared to the Arctic transmission loss simulation (B). Transmission loss in dB plotted as a function of range and depth. Surface ducting keeps sound generated near the surface propagating at the surface over great distances.
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Map C shows acoustic sim- CD ulation at 100-m depth of a
fictitious grid of 16 vessels spaced 200-km apart in the South Pacific Ocean. The region is fairly quiet. Map D shows acoustic simulation at 100-m depth of the same grid of 16 vessels spaced 200-km apart in the Arctic Ocean. The entire region is ensonified.
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Depth (km) Depth (km) Depth (km)