![]() ![]() Just like convection in air, when denser water sinks, its space is filled by less dense water moving in. More dense water masses will sink towards the ocean floor. A water particle in the convection cycle can take 1600 years to complete the cycle. The blue arrows are deep currents and the red ones are surface currents.įigure 14.17: Surface and deep currents together form convection currents that circulate water from one place to another and back again. So, cold water has greater density than warm water.įigure 14.16: Thermohaline currents are created by differences in density due to temperature (thermo) and salinity (haline). Colder water takes up less space than warmer water (except when it freezes). This is because temperature affects volume but not mass. Temperature also affects density: the colder the temperature, the greater the density. The more salt that is dissolved in the water, the greater its density will be. Two major factors determine the density of ocean water: salinity (the amount of salt dissolved in the water) and temperature (Figure 14.16). If you put the two liquids together, the one with greater density would sink and the one with lower density would rise. Because the bottles are both of equal volume, the liquid in the heavier bottle is denser. 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. ![]() Density is the amount of mass in a given volume. These currents are not created by wind, but instead by differences in density of masses of water. Deep within the ocean, equally important currents exist that are called deep currents. Surface currents occur close to the surface of the ocean and mostly affect the photic zone. Currents are created by wind, and their directions are determined by the Coriolis effect and the shape of ocean basins. When the water reaches the edge, it has to change direction.įigure 14.15: This map shows the major surface currents at sea. Imagine pushing the water in a bathtub towards the end of the tub. When a surface current collides with land, it changes the direction of the currents. The third major factor that determines the direction of surface currents is the shape of ocean basins (Figure 14.15). The Coriolis Effect bends the direction of surface currents. Wind or water that travels toward the poles from the equator is deflected to the east, while wind or water that travels toward the equator from the poles gets bent to the west. As a result, an object moving north or south along the Earth will appear to move in a curve, instead of in a straight line. While wind or an ocean current moves, the Earth is spinning underneath it. This means that objects on the equator move faster than objects further from the equator. The further towards one of the poles you move from the equator, the shorter the distance around the Earth. The Earth is a sphere that spins on its axis in a counterclockwise direction when seen from the North Pole. The ‘Coriolis Effect’ describes how Earth’s rotation steers winds and surface currents (Figure 14.14). Wind is not the only factor that affects ocean currents. This hotter air rises up at the equator and as colder air moves in to take its place, winds begin to blow and push the ocean into waves and currents. The cooler air coming into the space left by the warm air is wind.īecause the Earth’s equator is warmed by the most direct rays of the Sun, air at the equator is hotter than air further north or south. Like a balloon, the light warm air floats upward, leaving a slight vacuum below, which pulls in cooler, denser air from the sides. The movement of hot chocolate throughout the cup forms a stream or current, just as oceanic water moves when wind blows across it.īut what makes the wind start to blow? When sunshine heats up air, the air expands, which means the density of the air decreases and it becomes lighter. The ripples in the cup are tiny waves, just like the waves that wind forms on the ocean surface. When you blow across a cup of hot chocolate, you create tiny ripples on its surface that continue to move after you’ve stopped blowing. ![]() The direction that they spin depend on the hemisphere that they are in.Ĭurrents on the surface are determined by three major factors: the major overall global wind patterns, the rotation of the Earth, and the shape of ocean basins. \)įigure 14.14: The Coriolis Effect causes winds and currents to form circular patterns. ![]()
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