Ocean water is continually in activity (Figure 14.7). From north to south, eastern to west, and up and down the shore, ocean water moves all over the place. These movements have the right to be explained as the an outcome of plenty of separate forces, including local problems of wind, water, the position of the moon and also Sun, the rotation the the Earth, and also the position of floor formations.

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Lesson Objectives

Describe how surface currents type and exactly how they impact the world’s climate.Describe the reasons of deep currents.Relate upwelling areas to their affect on the food chain.

Surface Currents

Wind the blows end the ocean water create waves. It additionally creates surface currents, which are horizontal streams the water that can circulation for hundreds of kilometers and can reach depth of thousands of meters. Surface ar currents are an important factor in the ocean because they room a major factor in identify climate about the globe.

Causes of surface ar Currents


Figure 14.14: The Coriolis Effect reasons winds and currents to kind circular patterns. The direction the they spin rely on the hemisphere that they space in.

Currents ~ above the surface ar are established by three significant factors: the major overall an international wind patterns, the rotation that the Earth, and also the shape of s basins.

When friend blow across a cup of warm chocolate, you develop tiny ripples ~ above its surface that proceed to move after you’ve quit blowing. The ripples in the cup room tiny waves, similar to the waves the wind forms on the ocean surface. The motion of hot chocolate throughout the cup creates a stream or current, just as oceanic water moves as soon as wind blows across it.

But what makes the wind begin to blow? once sunshine heats increase air, the air expands, which means the density of the wait decreases and also it becomes lighter. Favor a balloon, the light warm air floats upward, leaving a slight vacuum below, which traction in cooler, denser waiting from the sides. The cooler wait coming right into the space left through the warm air is wind.

Because the Earth’s equator is warmed by the most direct rays of the Sun, air in ~ the equator is hotter than air further north or south. This hotter air rises up at the equator and also as cooler air move in to take it its place, winds begin to blow and also push the ocean into waves and currents.

Wind is not the only factor that affects ocean currents. The ‘Coriolis Effect’ defines how Earth’s rotation steers winds and surface currents (Figure 14.14). The earth is a sphere that spins on its axis in a counterclockwise direction when seen indigenous the north Pole. The additional towards among the poles you move from the equator, the shorter the distance roughly the Earth. This method that objects ~ above the equator move faster than objects more from the equator. If wind or one ocean existing moves, the earth is spinning under it. Together a result, an object moving phibìc or southern along the earth will appear to move in a curve, instead of in a straight line. Wind or water that travels towards the poles indigenous the equator is deflected to the east, if wind or water that travels towards the equator from the poles it s okay bent to the west. The Coriolis impact bends the direction of surface ar currents.

The third significant factor that determines the direction of surface currents is the form of ocean basins (Figure 14.15). When a surface existing collides with land, it changes the direction of the currents. Imagine pushing the water in a bath tub towards the end of the tub. When the water will the edge, it has to readjust direction.


Effect on global Climate

Surface currents beat a big role in determining climate. These currents bring warm water native the equator come cooler parts of the ocean; lock transfer heat energy. Let’s take the Gulf Stream as an example; girlfriend can uncover the Gulf present in the phibìc Atlantic ocean in figure 14.15. The Gulf present is an ocean current that transports warm water native the equator previous the east coast of north America and across the Atlantic come Europe. The volume the water that transports is an ext than 25 times the of every one of the rivers in the people combined, and the energy it transfers is more than 100 time the world’s power demand. It is around 160 kilometers wide and about a kilometer deep. The Gulf Stream’s heat waters offer Europe a much warmer climate 보다 other places at the same latitude. If the Gulf Stream to be severely disrupted, temperatures would certainly plunge in Europe.

Deep Currents

Surface currents occur close to the surface of the ocean and mostly affect the photic zone. Deep within the ocean, equally important currents exist that space called deep currents. These currents space not produced by wind, however instead by distinctions in thickness of masses the water. Thickness is the amount of mass in a provided volume. Because that example, if you take two complete one liter party of liquid, one could weigh more, the is it would certainly have higher mass than the other. Due to the fact that the bottles room both of same volume, the fluid in the heavier bottle is denser. If you placed the two liquids together, the one v greater thickness would sink and the one with lower thickness would rise.

Two major factors determine the thickness of s water: salinity (the amount of salt dissolved in the water) and temperature (Figure 14.16). The an ext salt the is liquified in the water, the greater its density will be. Temperature also affects density: the cooler the temperature, the higher the density. This is because temperature influence volume however not mass. Cooler water takes up less room than warmer water (except once it freezes). So, cold water has greater density than warm water.



More thick water masses will sink towards the ocean floor. As with convection in air, once denser water sinks, its an are is filled by less thick water moving in. This creates convection currents that relocate enormous quantities of water in the depths of the ocean. Why is the water temperature cooler in some places? Water cools together it move from the equator to the poles via surface ar currents. Cooler water is an ext dense so it starts to sink. As a result, the surface currents and also the deep currents room linked. Wind reasons surface currents to transport water roughly the oceans, while density differences cause deep currents come return the water back around the globe (Figure 14.17).


As you have seen, water that has actually greater density usually sinks to the bottom. However, in the right conditions, this procedure can it is in reversed. Denser water native the deep ocean deserve to come approximately the surface in one upwelling (Figure 14.18). Generally, one upwelling occurs along the coast when wind blows water strongly far from the shore. As the surface water is blown far from the shore, cooler water from listed below comes as much as take that is place. This is vital process in areas like California, south America, southern Africa, and the Arabian Sea because the nutrients brought up indigenous the deep s water support the expansion of plankton which, in turn, supports various other members in the ecosystem. Upwelling additionally takes ar along the equator between the North and South Equatorial Currents.

Lesson Summary

Ocean tide are power traveling through the water.The highest portion of a wave is the crest and the shortest is the trough.The horizontal distance between two tide crests is the wave’s length.Most tide in the s are wind created waves.Ocean surface ar currents are developed by major overall trends of atmospheric circulation, the Coriolis Effect and the shape of each s basin.Ocean surface circulation brings warmth equatorial waters in the direction of the poles and also cooler polar water towards the equator.Deep s circulation is thickness driven circulation created by differences in salinity and also temperature of water masses.Upwelling locations are biologically important locations that type as ocean surface waters space blown far from a shore, leading to cold, nutrient rich waters to rise to the surface.

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Review Questions

What determinants of wind recognize the dimension of a wave?Define the crest and trough of a wave.What is the most far-reaching cause the the surface ar currents in the ocean?How do ocean surface currents impact climate?What is the Coriolis Effect?Some scientists have actually hypothesized the if enough ice in Greenland melts, the Gulf Stream could be closeup of the door down. There is no the Gulf stream to lug warm water northward, Europe would become much colder. Define why melting ice in Greenland might influence the Gulf Stream.What procedure can make denser water climb to the top?Why are upwelling areas important to naval life?


amplitudeThe vertical height of a wave, measured indigenous trough come crest.Coriolis effectThe apparent deflection the a moving object prefer water or air resulted in by Earth’s rotation.crestThe highest point in a wave.deep currentA existing deep within the ocean, which moves since of density differences (caused by distinctions in water temperature and salinity).rip currentA solid surface present of water that is return to the s from the shore.surface currentA horizontal activity of s water, led to by surface ar winds.troughThe lowest point in a wave.tsunamiA seismic sea wave created by vertical activity of the s floor underwater earthquake, underwater volcanic eruption or landslide or meteorite impact.upwellingCold, nutrient-rich water the rises indigenous oceanic depth usually close to the continents, once wind blows the overlying surface away or follow me the equator.waveA readjust in the shape of water led to by energy moving with the water.wavelengthThe horizontal distance between two troughs, or 2 crests in a wave.