1. Momo An Anni Eloyan Heather Wright Geology 12 #7341
SOFAR CHANNEL
Momo An
Anni Eloyan
Heather Wright
Geology 12 #7341

2. Discovery of the SOFAR Channel
The two scientists that lead to the discovery of the SOFAR channel are Maurice Ewing and J.Lamar Worzel. They conducted research on acoustics in the ocean that helped the navy detect enemy submarines or mines, and also helped the U.S to avoid detection.
Also the SOFAR Channel was known as the “deep sound channel” which was discovered by Russian expert in acoustics Leonid Brekhovskikh.
However, Ewing and Worzel predicted in their discovery, that low frequency sound waves are able to travel greater distances than higher frequency waves, due to the fact that lower frequencies are less likely to be scattered and absorbed in the deep ocean.

3. In Honor of our Discoverers

4. Testing the Hypothesis
In 1943, Maurice Ewing and J. L Worzel hypothesized that the sound can travel long distances in the channel to the test.
To test this hypothesis: Both scientists set off an explosion underwater with 1 pound of TNT in the Bahamas. To their satisfaction, the sound was detected 2,000 miles away on the coast of West Africa.

5. Introduction of the SOFAR Channel
SOFAR Channel: Sound Fixing and Ranging Channel
SOFAR channel tends to be located in a layer in the deep ocean (1km in depth). The sound that is produced in the deep ocean, travels long distances without any specific amounts of sound getting to the surface.
The SOFAR Channel tends to be a wave detector, which measures the sound of the ocean movement due to the temperature and pressure differences based on the depth of the ocean.
Sound speed ↑ with increase in pressure. However, the sound speed ↓ due to decrease in water temperature( 5m/℃).
The origin of the SOFAR channel, is the way that the velocity of sound differs in water due to the function of ocean.

6. SOFAR Channel
Normally, the ocean is divided into horizontal layers and the temperature in the ocean is measured at the surface layer, whereas the pressure is measured at the deep layer of the ocean.
The presence of sound channeling takes place ,due to the minimum at the vertical sound speed profile in the ocean which is caused by changes of density in the water. The density becomes affected by temperature, pressure, and salinity. These effects cause a change in the speed of sound in the water, due to the change in density.
In the ocean : as temperature⇩, the speed of sound ⇩, where the pressure (depth) ⇧, the speed of sound ⇧.

7. Movement of Sound Waves
The SOFAR channel detects how the waves tend to “bend” downward as the speed of the sound decreases when ⇩ temperature, but waves rise back upward as the speed of sound ⇧ and ⇧ pressure increases.
Thermocline: rapid change in temperature ⇨
Scientists have found that sound waves have been trapped in the narrow SOFAR channel due to refraction. They are continually refracted in the area from where the bottom of the thermocline meets the top of the deep isothermic layer.
Waves may bend downward again as warming temperatures cause sound velocity to increase.

8. Hydrophones Hydrophones are basically underwater microphones
Hydrophones are devices used to listen to sound underwater. They convert sound in water into electrical signals which are then amplified, recorded, and played on loudspeakers to measure the property of sound
Hydrophones listen and record sound, but they do not make any sound

9. Hydrophones & SOFAR Channel

10. Sound Travelling
Every time travelling sound hits the sea floor, energy is lost and scattered and is very hard to detect.
Yet even if sound does not hit the sea floor, a very small amount of energy will still be lost to absorption.
Low frequency sounds that have not hit the ocean surface or sea floor can then travel through the channel and still be detected.
The sound travels with minimal velocity and can travel distances up to 15,500 miles.

11. Sound Speed Graph

12. SOFAR Channel in the ocean
In the ocean, sea animals such as whales use the SOFAR channel to send sounds across the ocean basins. They can collaborate even though they are far from one another like from Asia to America.
This video depicts the types of sounds that are collaborated within the presence of sea animals and humans( arriving in boats and submersibles)

13. Continuation…….
Prior to the widespread use of GPS(global positioning system) equipment, the SOFAR channel also was used for navigation and the location of marine craft. Some scientists hypothesize that certain species of whales use the SOFAR channel to communicate mating calls through long distances.

14. Cont… SOFAR Channel ATOC(Acoustic Thermometry of Ocean Climate)
A project that provides data to measure changes in global temperature.
What to expect? It will provide evidence related to questions as regards to global warming.
The SOFAR Channel is a beneficial
tool to measure the oceanic
climate during the ATOC project.

15. SOFAR Channel & ATOC ATOC(Acoustic Thermometry of Ocean Climate)
Q: How does the SOFAR channel help in the ATOC project?
A: The SOFAR Channel is beneficial by measuring differences in the speed of sound that is passed on over long distances , especially across basins, the data collected over time averages the variations in temperature and salinity, and helps ATOC scientists to calculate changes of the ocean temperature .

16. The End !!!!!!!