Page 48 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition
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36 CHAPTER 2 The Ocean Environment
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FIGURE 2.8
333435 Salinity (PSU)
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4900 4950 5000 Sonic velocity (f/s)
Temperature (°C)
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Sonic velocity (m/s)
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Sonic velocity profiles with varying temperature/salinity/depth.
ocean. A change in overall water density over short range due to any of these three variables (or in combination) is termed a “pycnocline.” Overall variations of pressure and temperature are depicted graphically in Figure 2.9.
This layering within the ocean, due to relatively impervious density barriers, causes the forma- tion of sound channels within bodies of water. These “channels” trap sound, thus directing it over possibly long ranges. Sound will refract based upon its travel across varying density layers, bending toward the denser water and affecting both range and bearing computations for acoustics (Figure 2.10). Over short ranges (tens or hundreds of meters) this may not be a substantial number and can possibly be disregarded, but for the longer distances of some larger ROV systems, this becomes increasingly a factor to be considered.
Salinity
Temperature
Depth (m)
Depth (m)
