Transcript Slide 1
THE WATER PLANET OCEAN CURRENTS VOCABULARY OCEAN CURRENTS AND ATMOSPHERE Surface Current Deep Current Salinity Boundary Current Coriollis Effect Gyre Ozone Particulates Albedo Atmospheric Pressure Greenhouse Effect Prevailing Winds OBJECTIVES: Name the major divisions of the global ocean Describe how wind patterns, the rotation of the Earth, and continental barriers affect surface currents Identify the major factor that determines the direction in which a surface current circulates Explain how differences in the density of ocean water affects the flow of deep currents Three quarters of Earth’s surface is covered by a body of salt water called the global ocean. The global ocean contains more than 97% of all of the water on Earth. Yet, as prominent a feature as it is, it makes up only 1/4000 of the Earth’s total mass and 1/800 of the total volume. The global ocean is divided into 5 major oceans. These major oceans are the: Atlantic Pacific Indian Arctic Southern Oceans (Antarctic) The Pacific ocean is the world’s largest It contains more than ½ of all ocean water. With an average depth of 4.3 km it is also the world’s deepest ocean. The Atlantic is the second largest ocean. The Atlantic has an average depth of 3.9 km. The Indian Ocean is the third largest ocean. The average depth is also 3.9 km. The southern is the 4th largest ocean and surrounds the continent of Antarctica out to 60 degrees south latitude. The smallest ocean is the Arctic ocean which surrounds the north pole A sea is a body of water that is smaller than an ocean and that may be partially surrounded by land. Examples are: Caribbean Sea South China Sea Mediterranean Sea CURRENTS The water in the ocean moves in giant streams called currents Currents that move on or near the surface of the ocean and are driven by winds are called surface currents. All surface currents are affected by winds. Winds are caused by the unequal heating of the Earth’s atmosphere. Because wind is moving air, wind has kinetic energy. The wind passes this energy to the ocean as the air moves across the ocean surface. WIND OCEAN SURFACE SURFACE CURRENT Global wind belts and ocean currents do not flow in straight lines. They follow a curved path or circular pattern caused by Earth’s rotation. This curving path is called the Coriolis Effect The wind belts on Earth and the Coriolis Effect cause huge circles of moving water called Gyres. Coriollis causes the wind to veer to the right A similar motion will occur with the ocean current as well. Air will flow into the center of a low pressure system. (red arrows) The coriollis causes the winds to move to the right. (purple arrows) Air in high pressure moves outward from the center. Coriolis causes the same right deflection as in the low This creates a phenomena known as the Eckman Spiral in both the ocean (left) and the atmosphere (right). The map shows the world’s major surface currents. In the northern hemisphere these currents move clockwise, in the southern hemisphere they move counterclockwise. This is the North Atlantic Gyre. The Gulf Stream pulls warm water out of the Gulf of Mexico and the Caribbean Sea. The Gulf Stream is what is known as a boundary current Boundary currents have characteristics determined by the presence of a coastline. In addition to having wind blown surface currents the oceans also have deep currents. Deep currents are far below the surface and move more slowly than surface currents. Deep currents form as cold, dense water from the polar regions sinks and flows beneath the warmer surface waters. The movement of these waters is the result of differences in density. Cold water is more dense than warm water. Salinity is also a factor in density. When water freezes, the salt in the water does not freeze, but stays in the unfrozen water. Water in polar regions therefore is more dense. The dense polar water sinks below the surface water forming a deep current.