For example, if you take two full one liter bottles of liquid, one might weigh more, that is it would have greater mass than the other. Because the bottles are both of equal volume, the liquid in the heavier bottle is denser. If you put the two liquids together, the one with greater density would sink and the one with lower density would rise.
Two major factors determine the density of ocean water: salinity the amount of salt dissolved in the water and temperature Figure The more salt that is dissolved in the water, the greater its density will be. Temperature also affects density: the colder the temperature, the greater the density. This is because temperature affects volume but not mass. Colder water takes up less space than warmer water except when it freezes.
So, cold water has greater density than warm water. The blue arrows are deep currents and the red ones are surface currents. A water particle in the convection cycle can take years to complete the cycle.
More dense water masses will sink towards the ocean floor. Just like convection in air, when denser water sinks, its space is filled by less dense water moving in. This creates convection currents that move enormous amounts of water in the depths of the ocean.
Why is the water temperature cooler in some places? Water cools as it moves from the equator to the poles via surface currents. Cooler water is more dense so it begins to sink. As a result, the surface currents and the deep currents are linked. Wind causes surface currents to transport water around the oceans, while density differences cause deep currents to return that water back around the globe Figure As you have seen, water that has greater density usually sinks to the bottom.
However, in the right conditions, this process can be reversed. Denser water from the deep ocean can come up to the surface in an upwelling Figure Generally, an upwelling occurs along the coast when wind blows water strongly away from the shore. Global ocean currents and thermohaline circulation Read the link below. Recall from Lesson 3 that water density increases with increasing salinity and decreasing temperature. Water density varies throughout the ocean and the water at the bottom of the ocean is densest, of course.
Surface currents are controlled by three factors: global winds, the Coriolis effect, and continental deflections. Different winds cause currents to flow in different directions.
Surface currents in the ocean are driven by global wind systems that are fueled by energy from the sun. Surface wind-driven currents generate upwelling currents in conjunction with landforms, creating deepwater currents. Currents may also be caused by density differences in water masses due to temperature thermo and salinity haline variations via a process known as thermohaline circulation.
These currents move water masses through the deep ocean—taking nutrients, oxygen, and heat with them. Occasional events such as huge storms and underwater earthquakes can also trigger serious ocean currents, moving masses of water inland when they reach shallow water and coastlines.
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