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  • 1. Earth’s Ocean Mrs. Harsh 6 th Grade Earth Sci.
  • 2. Facts about the Ocean
    • 71% of earth’s surface is covered by water.
    • 5 main oceans.
      • Largest ocean: Pacific Ocean
        • Second largest: Atlantic Ocean
        • Smallest: Arctic Ocean
        • Terms Sea and Ocean are interchangeable.
        • Parts of the global ocean that are partly surrounded by land are known as seas.
  • 3. Characteristics of Ocean Water
    • Not safe to drink!
    • Most salt in ocean = sodium chloride (same kind we put on food)
    • Salt has been added for millions of years.
      • As water flows toward oceans, it dissolves minerals on land. Running water carries dissolved minerals to the ocean.
      • Water is evaporating, leaving dissolved minerals behind. See Page 376 for pie chart.
  • 4. Cool Ocean Facts:
    • If the salt in the sea could be removed and spread evenly over Earth's land surface it would form a layer more than 500 feet thick, about the height of a 40-story building.
    • Seawater is 220 times saltier than fresh lake water
    • The weight of water is over 28.5 times greater than the weight of salt it contains
  • 5. Salinity
    • Oceanographers use the measure of salinity to describe the relative amount of salt to water.
    • Some parts of the ocean are saltier than others.
    • North Atlantic ocean is the saltiest.
    • Climate Affects Salinity
    • Coastal water in hotter, dryer climates = high salinity.
    • Water evaporates more, leaving salt behind.
    • lower salinity generally occurs where precipitation is greater than evaporation
  • 6.  
  • 7. Water Movement Affects Salinity
    • Some parts of the ocean move more than others.
    • Bays, gulfs, and seas move less than other parts.
    • Parts of the open ocean that do not have currents running through them can be slow moving.
    • Slower moving areas of water develop higher salinity.
  • 8. Temperature Zones of Ocean Water
    • Temp. ↓ as depth increases.
    • Heating of the ocean occurs during daylight & is warmest in late afternoon. More energy is absorbed when sun is high in sky, and less when the sun is near horizon
    • Water in the ocean can be divided into 3 layers by temperature.
    • Surface Zone- contains less dense water, usually as a result of higher temp. caused (water neutral) by warming of the sun. Extensive mixing.
    • Thermocline Zone- not uniform in temperature like the Surface Zone and Deep Zones. It represents the transition between the two zones. Temp. drops faster here with increased depth than other two zones.
    • Deep Zone - The Deep Zone is the bottom layer. The water in the Deep Zone remains cold and dense.
  • 9. Global Thermostat
    • Large part of the oceans roll: absorb and hold energy from sunlight.
    • The ocean absorbs and releases thermal energy much slower than dry land does.
      • If there were no ocean, the atmosphere could vary from 100 degrees C to -100 degrees C. The rapid exchange of thermal NRG between earth’s surface & atmosphere would cause violent weather patterns.
  • 10. Current Changes Weather
    • Heated water near equator causes some coastal land to have warmer climates than they would have without the currents.
  • 11. Sonar : Sound Navigation and Ranging
    • Based on the echo-ranging behavior of bats.
    • Used to determine the ocean’s depth by sending sound pulses from the ship to the ocean floor.
    • The deeper the water, the longer the pulses take to return to the ship.
    • Scientists then calculate the distance by multiplying ½ the travel time by the speed of sound in water (1500 m/s).
  • 12. Oceanography via Satelite
    • Satellites send images back to earth that allow scientists to measure the direction and speed of ocean currents.
    • Satellite oceanography is one of the rapidly growing fields in modern oceanography, and it has an expanding role in all areas of ocean and climate research. New sensors are under development to measure salinity and velocity, and new analysis techniques are being developed to better interpret existing measurements.
  • 13. Ocean Currents
    • A movement of ocean water that follows a regular pattern.
    • Surface currents: a horizontal movement of ocean water that is caused by wind and that occurs at or near the ocean’s surface.
      • Can reach depths of several hundred meters & lengths of thousands of km.
      • Gulf Stream transports water 25 x’s more water than all the rivers in the world.
      • Controlled by: global winds, Coriolis effect, & continental deflections.
  • 14. Compare Rivers & Surface Currents
    • Both are long & moving bodies of water.
    • Rivers flow because of the pull of gravity
    • Surface currents are driven by wind and the rotation of the earth.
    • Surface currents make up about 10% of all the water in the ocean. Surface currents are generally restricted to the upper 400 m (1,300 ft) of the ocean.
    • Device used to measure ocean currents.
  • 15. Global Winds
    • Winds that blow across the Earth’s surface create surface currents in the ocean.
    • Near the equator, winds blow from East to West but near the poles, ocean water is blown west to east.
    • Ships use this information to travel more quickly back and forth across the ocean.
  • 16. Coriolis Effect
    • The apparent curving of the path of a moving object from an otherwise straight path due to the Earth’s rotation.
    • Causes surface currents in the Northern Hemisphere to turn clockwise, and surface currents in the Southern Hemisphere to turn counterclockwise.
    • See Page 419 figure 6 for visual.
  • 17. Continental Deflections
    • If the earth was covered w/ water, surface currents would travel freely across the globe.
    • When surface currents meet continents, the currents deflect, or change direction.
  • 18. Deep Currents
    • Streamlike movements of ocean water located far below the surface.
    • Deep currents are not controlled by wind.
    • Form in parts of the ocean where water density increases.
      • Density is affected by salinity and temperature.
        • Increasing salinity and decreasing of temp. increases the water’s density.
  • 19. Deep Currents Flow
    • Differences in density determines the depth of the current.
    • Currents can flow directly toward each other and on top of each other due to the different levels of density.
      • Cooler water is more dense
      • Dissolved solids are squeezed out of the ice & enter the liquid water below the ice causing salinity to increase = increased density
      • Evaporation increases salinity = higher density.
  • 20. Surface Currents Affect Climate
    • Warm Water Current: Create warmer climates in coastal areas that would otherwise be much colder.
    • Cold water surface currents: California current carries water toward Mexico & keeps Cal. Cooler than inland climate year round.
  • 21. California Cold Currents
    • Upwelling Brings Cold Water Up From Below
    • California’s beaches have cold water coming from the north, but they also have cold water coming from its own depths. Water at the surface gets more sunlight than water deeper down. Thus, water is warmer at the surface and colder at depth. Upwelling is the movement of deep cold waters coming to the top and is caused by wind. When wind blows parallel to a coastline, as it does off the California coast, it can move water at a right angle to the direction the wind is blowing. This movement is aided by the Coriolis effect . So, as water at the surface is being pushed away from the coast, water is drawn from below to replace it. That is, cold chilly water coming to the surface.
    • Upwelling Brings Cold Water Up From Below
    • California’s beaches have cold water coming from the north, but they also have cold water coming from its own depths. Water at the surface gets more sunlight than water deeper down. Thus, water is warmer at the surface and colder at depth. Upwelling is the movement of deep cold waters coming to the top and is caused by wind. When wind blows parallel to a coastline, as it does off the California coast, it can move water at a right angle to the direction the wind is blowing. This movement is aided by the Coriolis effect . So, as water at the surface is being pushed away from the coast, water is drawn from below to replace it. That is, cold chilly water coming to the surface.
  • 22. The Intertidal Zone
    • Located between the low-tide and high-tide limits.
    • Organisms that live there must be able to live in water and on exposed land.
    • Changes twice a day.
    • Some animals attach themselves to rocks so they are not swept out to sea during low tide….clams, oysters, starfish.
  • 23. Tides
    • Daily changes in the level of ocean water.
    • Tides are influenced by the sun and the moon.
    • How often tides occur & the difference in tidal levels depend on the position of the moon as it revolves around the earth.
    • Moon’s pull is strongest on the part of the Earth directly facing the moon.
  • 24. Battle of the Bulge
    • When part of the ocean is directly facing the moon, the water there bulges toward the moon.
    • At the same time, the opposite side bulges due to the Earth’s rotation & the motion of the moon around the earth.
    • If the Earth & moon rotated at the same speed, tides would not alternate between high and low.
    • Moon rotates around the earth much slower than the earth rotates.
      • Spring tides occur when earth and moon are alligned. Largest daily tidal range.
        • Occur at new & full moon (every 14 days)
        • Neap Tides : Sun & moon are at right angles to ea. other.
        • Gravitational forces work against each other. Smallest daily tidal range. (P. 434)
  • 25. Sites used:
    • http://www.theoceans.zoomshare.com/9.html
    • http://aquarius.nasa.gov/education-salinity.html
    • http://marinebiologyoceanography.suite101.com/article.cfm/why_californias_beaches_are_cold