PHYSICAL OCEANOGRAPHY

Part 4: Sound in the Ocean

GEOL 1033

(Lesson 29)

SOUND IN SEAWATER

• Sound travels – About 4 times faster in water than in air– Approximately 1 500 m/s in water

• Depth determination (study Exercise #4)– Half travel time X 1500 m/s = depth

• Echo sounder used– Record depth profiles– Detects deep scattering layers– Obtain seismic profiles

Speed of Sound in Water

• “Typical” depth profile of sound speed in seawater

Speed of Sound in Water

• Arctic & Antarctic profile

• Lower latitude profile

SOFAR & Shadow Zone

• Effects of sound speed minimum and maximum:

SOFAR Channel

• Sound velocity minimum at about 1000 m depth at low to mid latitudes

SOFAR Experiment in 1991

• Successful transmission of sound over great distance

Sound Shadow Zone

• Associated with a near-surface sound maximum speed depth

• At approximately 80 to 100 m

Ideal detection

Sound "Shadow Zone" Due to Refraction

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