Cromwell current
|
|
The Cromwell current (also called Pacific Equatorial Undercurrent or just Equatorial Undercurrent) is a submarine river: A particular kind of ocean current that is, in effect, a river flowing under the surface of an ocean.
Submarine rivers are a fascinating and relatively new field of oceanography. These beautiful mysteries of the nature show us that we humans have still lots of things to discover.
The Cromwell current was discovered in 1952 by Townsend Cromwell a researcher with the Honolulu Laboratory. It is 250 miles (400 km) wide and flows to the east. It is hidden 300 feet (100 m) under the surface of the Pacific Ocean at the Equator it is relatively narrow in depth compared to other ocean currents being only 100 feet deep. It has 1000 times the volume of Mississippi and its length is 3500 miles.
The Cromwell current was listed in the 1964 edition of the Guinness Book of World Records.
| Contents |
Townsend Cromwell
Townsend Cromwell, a keen surfer, swimmer and oceanographer, discovered the current that now bears his name whilst researching drifting in the equatorial region of the Pacific Ocean. He died in 1958 when his plane crashed while he was enroute to an oceanography expedition.
Discovery
In 1951 researchers on board the U. S. Fish and Wildlife Service research vessel were indulging in a spot of long line fishing. They noticed that the gear deep under water drifted eastwards. This was unusual because the surface currents of the pacific ocean flow westwards on the equator. (They follow the direction of the winds).
The following year Townsend Cromwell led a research party to investigate how the currents of the ocean varied as a function of depth. They discovered a fast flowing current that flowed eastwards in the deep surface layers.
Detailed data
- Depth: The surface currents flow west. There is reversal point about 40 m down, where the water starts to flow east. The current goes down to about 400 m.
- Flow rate:The total flow is up to around 30 000 000 cubic meters per second. The top speed is around 1.5 m/s (this is about twice as fast as the westerly surface current)
- Length:13,000 km
Interaction with El Niño
El Niño is a reversal of the normal situation in the Pacific Ocean. Surface water is blown westwards by the prevailing winds and deeper water is forced upwards to replace it. Every now and then, the surface water sloshes back across the ocean, bringing warm water temperatures along the eastern coasts of the pacific. In non-El Niño years, the Cromwell current is forced to the surface by underwater volcanoes near the Galapagos islands. (This is called upwelling) However during El Nino years the current does not upwell in this way. The waters around the islands are therefore considerably warmer during el nino years than during normal years.
Effect on wildlife
The Cromwell Current is both oxygen and nutrient rich. A large number of fish are concentrated in it. Upwelling occurs near the Galapagos islands. This brings food supplies to the surface for Galapagos penguins. Upwelling however is a sporadic phenomenon,it fails to occur on a regular basis and so the food supply comes and goes. The penguins have several adaptations to cope with this, including versatility in their breeding habits.
Possible effect on climate
The effect of this current on world climate is not well understood, at the present time.
See also
External link
- Surface Ocean Currents (http://www.personal.psu.edu/users/a/x/axm368/)vi:Hải lưu Cromwell