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Rivers in the Sea Weather Dynamics Science 10 Ocean Currents • Surface winds start a process which creates giant rivers in the seas, also known as ocean currents. • Warm water is pushed from the equator to the poles • Cool water is pushed from the poles to the equator. • Two other factors that affect/create ocean currents are continents and the Coriolis effect. • Why would continents affect ocean currents? Ocean Currents • Ocean currents are blocked and diverted by continents, causing them to bend and turn. • The Coriolis Effect influences ocean currents in the same way it influences the wind. Due to the rotation of the Earth on its axis, the oceans two are in constant motion. • Ocean currents turn to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Gyres Gyres • All 3 factors mentioned create the ocean currents • When we look at ocean currents on Earth a pattern emerges. • Ocean current tend to flow in circular currents all around the Earth. • These circular currents are called Gyres. • They flow clockwise in the Northern Hemisphere and counter-clockwise in the Southern Hemisphere. Eastern side of Gyres • The right or east side of Gyres are cool. • This cooler current caues the air above it to be cool as well. • This cooler air cannot hold as much water vapour as warm air. • Consequently, if this air moves ashore, there is little condensation and very few clouds form here. • Some of these regions are even desert like due to small amounts of precipitation. Western Side of Gyres • The left or west side of most gyres are warm. • Thus, in these areas large amounts of water vapour exist in the air. • When this warm, humid (saturated) air moves ashore, rain often follows. • Hence rain forests and lush jungles forming here. • The warm currents warm the air. • Therefore, some climates near these gyres are warmer than they should be for their latitude. Great Ocean Conveyer Belt • Ocean currents do not just move water around from the equator to the poles. • Ocean water below 100m in the ocean is not affected by the Earth’s wind. • Ocean water at these depths move vertically up and down. Great Ocean Conveyer Belt • Cold water, like cold air, is more dense than warm water, and therefore sinks. • Cold water from the poles flows deep in the ocean until it reaches a warmer zone closer to the equator. • Here the water warms and rises in the ocean. • This occurs more than once during the extensive travels of water in the ocean, warming and cooling depending on its location. Great Ocean Conveyer Belt • The ocean conveyer belt is important for transporting energy and nutrients from pole to pole, around the Earth. • Many species of fish, krill, and other shellfish rely on the ocean conveyer belt to sustain life. Upwelling • If a constant wind blows from shore, it blows the water on the surface of the ocean out from shore as well. • These leaves a low density area for colder water to rise up along the coast. This is called an upwelling. • Upwellings bring up rich nutrients that have settled on the bottom of the ocean. • Schools of fish are attracted to areas where upwellings occur for this reason, and are therefore excellent places for fishermen to fish. Trade Winds • Upwellings occur off the west coasts of continents within or near tropical climates. • This is because trade winds which blow toward the equator from east to west, blow the water away from shore on the western coasts of continents near the equator. El Niño • Trade winds blowing water westward, causes it to pile up on shores like Australia (to the east) and warm. • For a reason still unknown today, at times the trade winds will diminish and actually blow in the opposite direction, pushing the warm water from the east westward. • The normally cooler water is suddenly warmed very quickly and is called El Niño. • At times the temperature changes can be very severe. El Niño • Some of the most severe El Niño's from the past have caused worldwide problems: – The temperature decrease on the East causes droughts due to loss of water vapour in the air. – The temperature increase on the West causes floods, monsoons, and severe storm systems due to the increases water vapour in the air. – The red tide, a huge algae bloom which flourish due to increased temperatures in nutrient rich water also form. The Red Tide • El Niño has been known to be a factor in promoting algae blooms in the ocean. • What are some of the problems that might be associated with this? • Algae, like other organisms in the ocean require carbon dioxide and other gases and nutrients to survive. • With a huge spike in algae, they use up all the carbon dioxide and nutrients in the water causing fish and other life forms to be starved of food and other resources. • Water based plants to die off due to lack of carbon dioxide to breath. • Plants cannot get light to utilize photosynthesis The Red Tide Do You Understand? 1. 2. 3. 4. 5. 6. Name three factors that determine the speed and direction of surface currents in oceans. Describe two ways that ocean currents can influence the climate of coastal regions. Under what conditions will cool water rise? Describe two events that occur while an El Niño is developing. What are some negative affects of El Niño? What is the red tide? Why is it bad?