The SOFAR channel ("SOund Fixing And Ranging channel"), or deep sound channel, is a layer of water deep in the ocean where the speed of sound is at a minimum. Within the SOFAR channel, low frequency sound waves may travel hundreds, if not thousands, of miles before dissipating. This phenomenon is an important factor in submarine warfare. The deep sound channel was descovered and described by Dr. Maurice Ewing, in the 1940s. The speed of sound is a term used to describe the speed of sound waves passing through an elastic medium. ... Naval warfare is divided into three operational areas: surface warfare, air warfare and submarine warfare. ... Dr. W. Maurice Ewing (May 12, 1906 – May 4, 1974) has been described as a pioneering geophysicist who worked on the research of seismic reflection and refraction in ocean basins, ocean bottom photography, submarine sound transmission, deep sea coring of the ocean bottom, theory and observation of earthquake surface waves... The 1940s decade ran from 1940 to 1949. ...

This channel exists at the depth where the cumulative effect of temperature and water pressure (and, to a smaller extend, salinity) combine to create the region of minimum sound speed in the water column. Pressure in the ocean rises linearly with depth, but temperature varies greatly, generally falling rapidly from the surface to around a thousand meters deep, then rising very slowly from there to the ocean floor. Near the surface, the rapidly falling temperature causes a decrease in sound speed; below the SOFAR channel, the increasing pressure causes an increase in sound speed. Near Bermuda, the lowest density water occurs at a depth of around 1000 metres. In temperate waters, this minimum sound depth is shallower, and it reaches the surface between latitudes of about 60 degrees N or 60 degrees S. Fig. ... Water pressure is the pressure in any system for supplying water, usually a domestic water system, although the term is used in other contexts as well, such as a municipal water system. ... Annual mean sea surface salinity for the World Ocean. ... Diagram of the layers of the pelagic zone. ... Latitude, usually denoted symbolically by the Greek letter phi, , gives the location of a place on Earth north or south of the equator. ...

The sound propagation in the channel is due to the refractionary tendencies of sound that makes it travel at the depth of its slowest speed (if a sound wave is drifting away from this horizontal channel, the part of the wave that is closer to the center of the SOFAR channel slows down and causes the wave to "turn" back to the slower depth). The straw seems to be broken, due to refraction of light as it emerges into the air. ...

Strange and mysterious low-frequency sounds, attributed to humpbacks and other baleen whales, are a common occurrence here. Scientists think that humpback whales may dive down to this channel and "sing" to communicate with other humpback whales many kilometers away. This article is about compression waves. ... Binomial name Megaptera novaeangliae (Borowski, 1781) Humpback Whale range The Humpback Whale (Megaptera novaeangliae) is a mammal which belongs to the baleen whale suborder. ... Diving refers to the sport of acrobatically jumping or falling into water. ...

During World War II, Maurice Ewing suggested that dropping a small metal sphere into the ocean, specifically designed to implode at the SOFAR channel, could be used as a secret distress signal by downed pilots. ^[1] Combatants Allied Powers Axis Powers Casualties Military dead: 17,000,000 Civilian dead: 33,000,000 Total dead: 50,000,000 Military dead: 8,000,000 Civilian dead: 4,000,000 Total dead 12,000,000 World War II (abbreviated WWII), or the Second World War, was a worldwide conflict... Dr. W. Maurice Ewing (May 12, 1906 – May 4, 1974) has been described as a pioneering geophysicist who worked on the research of seismic reflection and refraction in ocean basins, ocean bottom photography, submarine sound transmission, deep sea coring of the ocean bottom, theory and observation of earthquake surface waves...

The novel The Hunt for Red October describes the use of the SOFAR channel in submarine detection. The Hunt for Red October is Tom Clancys first novel, published in 1984. ...

References

1. ^ Sound Channel, SOFAR, and SOSUS. Robert A. Muller.

See also

• Bathythermograph (BT)
• Thermocline

The thermocline is a layer within a body of water where the temperature changes rapidly with depth. ...

External links

• The SOFAR or deep sound channel, from NOAA
• SOSUS, the "Secret Weapon" of Underwater Surveillance by Edward C. Whitman. Undersea Warfare