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Chapter 15 The Dynamic Ocean. Factors Influencing Surface Ocean Currents The ocean's surface currents follow the general pattern of the world's major.

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Presentation on theme: "Chapter 15 The Dynamic Ocean. Factors Influencing Surface Ocean Currents The ocean's surface currents follow the general pattern of the world's major."— Presentation transcript:

1 Chapter 15 The Dynamic Ocean

2 Factors Influencing Surface Ocean Currents The ocean's surface currents follow the general pattern of the world's major wind belts Gyres: o slowly moving loops of water o centered in the subtropics of each ocean basin o the positions of the continents and the Coriolis Effect affect water movement within gyres

3 Gyres: o Coriolis Effect:  An apparent force due to the Earth's rotation. Causes moving objects to be deflected to the right in the Northern Hemisphere and to the left in the Southern hemisphere. Coriolis force does not exist on the equator. This force is responsible for the direction of flow in meteorological phenomena like mid-latitude cyclones, hurricanes, and anticyclones.

4 Gyres: o Coriolis Effect:  causes subtropical gyres to move clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere o four main currents comprise each subtropical gyre o five main subtropical gyres:  Indian Ocean gyre  North Atlantic gyre  North Pacific gyre  South Atlantic gyre  South Pacific gyre

5 Deep-Ocean Circulation Deep-ocean circulation o Also referred to as thermohaline o It is caused by density variations  Density variations are caused by differences in temperature and salinity o Most water involved in deep-ocean circulation begins in high latitudes at the surface  Surface water becomes cold and salinity increases as sea ice forms o When water becomes dense enough, it sinks forming currents Deep-ocean circulation  Once it sinks, it stays the same temperature and salinity remain the same while in the deep-ocean o Antarctic water-surface conditions create the highest density water in the world  The water sinks to the seafloor  It moves throughout ocean basins in sluggish currents Deep waters will not resurface for years o Ocean-circulation is similar to a conveyer belt that travels from the Atlantic through the Indian to the Pacific

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7 Importance of Surface Ocean Currents Surface ocean currents have important effects on climate. o Currents moved from lower-latitude regions into higher latitudes transfer heat from warmer to cooler areas on earth. o Warm ocean currents which are felt in the middle latitudes in winter, the influence of cold currents is most pronounced in the tropics or during the summer months in the middle latitudes.  As the cold currents travel equatorward, they tend to moderate the warm temperature of adjacent land areas.  Cold currents are also associated with greater fog frequency and drought. Ocean currents also play a major role in maintaining Earth's heat balance. o they transfer heat from tropics, where there is excess amounts of heat, to the polar regions. Ocean currents also play an important role in navigation.

8 Importance of Surface Ocean Currents

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10 Upwelling o the rising of colder water from deep layers o wind-induced movement that brings cold, nutrient water to the surface o It also affects the movement of animals o vertical water movements o a common type of upwelling is coastal upwelling o brings greater concentrations of dissolved nutrients, such as nitrates and phosphates, to the ocean surface

11 Upwelling

12 Coastal upwelling Coastal Upwelling o most characteristic along the west coasts of continents (e.g; along California and western South America) o occurs when wind blows toward the equator o when combined with the Coriolis effect, water moves from the shore o slow upward movement of water from depths of 50 to 300 meters ( 165 to 1000 feet) brings water that is cooler than the original surface water and results in lower surface water temperatures near the shore

13 Coastal upwelling

14 Various Components of the Coastal Zone Shore o The area extending between the lowest tide level and the highest elevation on land that is affected by storm waves. o The coast extends inland from the shore as far as ocean-related features can be found. o The shore is divided into two parts.  Foreshore Seaward of foreshore are the nearshore and offshore zones.  Backshore Landward of the high-tide shoreline Usually dry, being affected by waves only during storms.  Nearshore Lies between the low-tide shoreline and the line where waves break at low tides.  Offshore Zone Seaward of the offshore zone.

15 Various Components of the Coastal Zone Shore  Beach An accumulation of sediment found along the landward margin of the ocean or a lake. May extend for tens/hundreds of km. along straight coasts. Formation may be confined to the quiet waters of bays.  Berms Relatively flat platforms often composed of sand that are adjacent to coastal dunes or cliffs and marked by a change in slope at the seaward edge.  Beachface Wet sloping surface that extends from the berm to the shoreline.

16 Works Cited "Coriolis Force." Definition. N.p., n.d. Web. 21 May 2013 "Ocean Gyre." Wikipedia. Wikimedia Foundation, 05 Sep Web. 21 May 2013.


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