Types of Vertical Currents

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    Types

    • There are four types of vertical currents in the oceans: coastal upwelling, equatorial upwelling, the upwelling in the southern ocean and the vertical currents of the Meridional Overturning Circulation--the ocean conveyor belt--that absorbs CO2 from the atmosphere and moves tropical heat around the Earth.

    Significance

    • Vertical currents are critical to the storage of heat in the ocean from summer to summer. This heat, when lost by the tropical regions of the oceans helps to moderate the Earth's climate.

    Time Frame

    • The waters that form these currents may take up to 1,600 years to travel through the "full circle" of the ocean general circulation, or OGC, before becoming part of an upwelling as a vertical current. Reported in the Journal of Physical Oceanography, a study by Francois Primeau demonstrated that waters in the upwellings in the Pacific and Southern oceans had been moving through the global ocean general circulation for about 1,600 years.

    Geography

    • The vertical currents of coastal upwellings occurs near the eastern coasts of the Atlantic and Pacific oceans. Winds blowing along the coasts cause the flow within the Ekman Layer to move perpendicularly to the wind direction--to the left in the southern hemisphere and to the right in the northern hemisphere--to direct its flow offshore, which forces water up from depths of 200 to 400 meters. The equatorial upwelling also occurs in the Atlantic and Pacific oceans as vertical currents about 5 degrees north and south of the equator and trade winds move through the area on either side of the equator.

      The conflict between the Ekman transport, flowing south, south of the equator and north, north of the equator, and the surface winds causes a surface divergence at the equator and forces water up from depths of 150 to 400 meters. The upwelling in the Southern Ocean occurs when the geostrophic flow from the North Atlantic deep water reaches the Southern Ocean at depths ranging from 1,000 meters to 4,000 meters. It then rises as vertical currents because of changes in the balance of the ocean's horizontal pressure gradient and Coriolis force when the currents approach the southern pole. It enters the Ekman Layer and moves into the Pacific's general circulation. The vertical currents of the Meridionial Overturning Circulation are found on both coasts of the Atlantic and the Pacific.

    Effects

    • The ocean is the largest reservoir of carbon dioxide on the planet, able to hold 50 times more CO2 than the atmosphere. Over the years, studies have show that vertical currents supply the "overturning" part of the ocean's circulation and, when carbon dioxide is absorbed into the ocean, either becoming part of the "soup" of sea water or by mixing, but not being absorbed by the water, these currents carry the CO2 into the depths and keep it there for long periods of time.

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