What happens to a current when it comes in contact with a continent or landmass?

Surface Currents

Ocean water moves in anticipated ways along the ocean surface.Surface currents tin can menses for thousands of kilometers and tin accomplish depths of hundreds of meters. These surface currents do not depend on weather; they remain unchanged fifty-fifty in big storms considering they depend on factors that practice not change.

Surface currents are created by three things:

• global wind patterns
• the rotation of the Earth
• the shape of the ocean basins

Surface currents are extremely important because they distribute rut around the planet and are a major cistron influencing climate effectually the globe.

Global Wind Patterns

Winds on Earth are either global or local. Global winds blow in the same directions all the time and are related to the unequal heating of Globe past the Dominicus — that is, more solar radiation strikes the equator than the polar regions –- and the rotation of the Earth — that is, theCoriolis effect. The causes of the global wind patterns volition be described in particular in the World's Atmosphere chapter.

Water in the surface currents is pushed in the direction of the major wind belts:

• trade winds: east to westward between the equator and xxx^oN and 30^oDue south
• westerlies: west to east in the eye latitudes
• polar easterlies: due east to west between fifty^o and 60^o north and due south of the equator and the north and south pole

Earth's Rotation

Wind is not the merely factor that affects ocean currents. The Coriolis event describes how World'due south rotation steers winds and surface ocean currents (Figure  below). Coriolis causes freely moving objects to announced to motion to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. The objects themselves are really moving straight, but the Globe is rotating beneath them, and then they seem to bend or curve.

An example might make the Coriolis effect easier to visualize. If an airplane flies 500 miles due due north, it will non make it at the urban center that was due north of it when it began its journey. Over the time information technology takes for the airplane to fly 500 miles, that urban center moved, along with the Earth it sits on. The airplane will therefore arrive at a city to the west of the original metropolis (in the Northern Hemisphere), unless the airplane pilot has compensated for the change. So to reach his intended destination, the airplane pilot must likewise veer right while flight northward.

As wind or an ocean electric current moves, the World spins underneath information technology. Equally a result, an object moving north or south forth the Earth will appear to motility in a bend, instead of in a straight line. Wind or water that travels toward the poles from the equator is deflected to the east, while wind or h2o that travels toward the equator from the poles gets bent to the west. The Coriolis upshot bends the direction of surface currents to the right in the Northern Hemisphere and left in the Southern Hemisphere.

The Coriolis event causes winds and currents to form circular patterns. The management that they spin depends on the hemisphere that they are in.

Coriolis effect is demonstrated using a metal ball and a rotating plate in this video. The ball moves in a circular path only like a freely moving particle of gas or liquid moves on the rotating World(5b): http://www.youtube.com/sentry?five=Wda7azMvabE (2:04).

Shape of the Ocean Basins

When a surface current collides with land, the current must change direction. In theFigure  below, the Atlantic South Equatorial Electric current travels westward forth the equator until it reaches South America. At Brazil, some of information technology goes northward and some goes south. Because of Coriolis consequence, the h2o goes right in the Northern Hemisphere and left in the Southern Hemisphere.

The major surface ocean currents.

Y'all tin see on the map of the major surface bounding main currents that the surface ocean currents create loops calledgyres (Effigy  beneath). The Antarctic Circumpolar Current is unique because it travels uninhibited effectually the globe. Why is it the only current to go all the fashion around?

The body of water gyres. Why do the Northern Hemisphere gyres rotate clockwise and the Southern Hemisphere gyres rotate counterclockwise?

This video shows the surface ocean currents prepare by global wind belts(5a): http://www.youtube.com/watch?v=Hu_Ga0JYFNg (i:20).

Issue on Global Climate

Surface currents play an enormous role in Earth'southward climate. Fifty-fifty though the equator and poles take very different climates, these regions would have more extremely different climates if ocean currents did not transfer estrus from the equatorial regions to the higher latitudes.

The Gulf Stream is a river of warm h2o in the Atlantic Sea, about 160 kilometers wide and about a kilometer deep. Water that enters the Gulf Stream is heated as it travels forth the equator. The warm water then flows up the east declension of North America and across the Atlantic Ocean to Europe (Figure  below). The energy the Gulf Stream transfers is enormous: more than 100 times the world's energy demand.

The Gulf Stream's warm waters raise temperatures in the North Body of water, which raises the air temperatures over land between 3 to 6oC (5 to 11oF). London, U.Chiliad., for example, is at the aforementioned breadth as Quebec, Canada. However, London'southward average January temperature is 3.8oC (38oF), while Quebec'southward is merely -12oC (10oF). Because air traveling over the warm water in the Gulf Stream picks upward a lot of water, London gets a lot of pelting. In contrast, Quebec is much drier and receives its precipitation equally snow.

In a satellite image of water temperature in the western Atlantic it is easy to pick out the Gulf Stream, which brings warmer waters from the equator upward eastern North America.

Deep CurrentsThermohaline circulation drives deep bounding main apportionment. Thermo ways oestrus and haline refers to salinity. Differences in temperature and in salinity change the density of seawater. So thermohaline circulation is the effect of density differences in water masses because of their unlike temperature and salinity.

What is the temperature and salinity of very dense h2o? Lower temperature and college salinity yield the densest water. When a book of water is cooled, the molecules move less vigorously so same number of molecules takes up less space and the h2o is denser. If common salt is added to a volume of h2o, there are more molecules in the aforementioned volume so the water is denser.

Changes in temperature and salinity of seawater take place at the surface. Water becomes dense nigh the poles. Cold polar air cools the water and lowers its temperature, increasing its salinity. Fresh water freezes out of seawater to become sea water ice, which too increases the salinity of the remaining h2o. This very cold, very saline water is very dense and sinks. This sinking is calleddownwelling.

This video lecture discusses the vertical distribution of life in the oceans. Seawater density creates currents, which provide different habitats for different creatures(5d): http://www.youtube.com/picket?v=LA1jxeXDsdA (six:12).

Two things and then happen. The dense water pushes deeper h2o out of its way and that h2o moves along the bottom of the ocean. This deep water mixes with less dense water as it flows. Surface currents move water into the space vacated at the surface where the dumbo water sank (Figure  below). Water too sinks into the deep body of water off of Antarctica.

Cold water (blueish lines) sinks in the North Atlantic, flows along the bottom of the body of water and upwells in the Pacific or Indian. The water and so travels in surface currents (red lines) back to the North Atlantic. Deep water also forms off of Antarctica.

Since unlimited amounts of water cannot sink to the bottom of the ocean, water must rise from the deep ocean to the surface somewhere. This procedure is calledupwelling (Effigy  below).

Upwelling forces denser h2o from beneath to take the place of less dense h2o at the surface that is pushed abroad by the wind.

Generally, upwelling occurs along the coast when wind blows water strongly abroad from the shore. This leaves a void that is filled by deep water that rises to the surface.

Upwelling is extremely important where it occurs. During its fourth dimension on the bottom, the cold deep water has collected nutrients that have fallen downward through the h2o cavalcade. Upwelling brings those nutrients to the surface. Those nutrient support the growth of plankton and form the base of a rich ecosystem. California, South America, Due south Africa, and the Arabian Sea all do good from offshore upwelling.

An animation of upwelling is seen here: http://oceanservice.noaa.gov/education/kits/currents/03coastal4.html.

Upwelling also takes place forth the equator between the North and South Equatorial Currents. Winds accident the surface water due north and south of the equator so deep h2o undergoes upwelling. The nutrients ascension to the surface and support a great bargain of life in the equatorial oceans.

Lesson Summary

• Ocean surface currents are produced by global winds, the Coriolis consequence and the shape of each bounding main basin.
• The Pacific and Atlantic Oceans have a circular pattern of surface currents called gyres that circle clockwise in the Northern Hemisphere and counterclockwise in the Southern. The Indian Bounding main merely has a counterclockwise gyre.
• Surface sea circulation brings warm equatorial waters towards the poles and cooler polar water towards the equator.
• Thermohaline circulation drives deep ocean currents.
• Upwelling of cold, nutrient-rich waters creates biologically rich areas where surface waters are blown away from a shore, or where equatorial waters are accident outward.

Review Questions

6. What causes the patterns of surface currents in the bounding main?
7. How do ocean surface currents bear upon climate?
8. What is the Coriolis effect?
9. What process can make deep, dense water rising to the surface?
10. Why are upwelling areas of import to marine life?

Further Reading / Supplemental Links

• Learn About Body of water Currents, v min. Life Videopedia http://www.5min.com/Video/Acquire-about-Ocean-Currents-117529352
• NOAA'due south Ocean Explorer plan http://oceanexplorer.noaa.gov/edu/welcome.html
• A tutorial for grades 6 to 12 on currents from NOAA: http://oceanservice.noaa.gov/education/tutorial_currents/welcome.html
• Cool jobs: Oceanographer http://news.discovery.com/videos/cool-jobs-absurd-jobs-oceanographer.html

Points to Consider

• Some scientists have hypothesized that if enough ice in Greenland melts, the Gulf Stream might be shut down. Why might this happen?
• If the Gulf Stream shuts downwardly, what would be the result on climate in Europe?
• How practise the movements of ocean water contribute to the ocean's life?

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Source: https://courses.lumenlearning.com/earthscience/chapter/currents/

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