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Unit 4- Physical Oceanography

Unit 4- Physical Oceanography. Currents. Ocean current- mass of ocean water that flows from one place to another Two types Surface/wind-driven Deep/density-driven. Coriolis Effect. Coriolis Effect- a “deflection ” of a moving object due to the fact that the Earth is rotating

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Unit 4- Physical Oceanography

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  1. Unit 4- Physical Oceanography

  2. Currents • Ocean current- mass of ocean water that flows from one place to another • Two types • Surface/wind-driven • Deep/density-driven

  3. Coriolis Effect • Coriolis Effect- a “deflection” of a moving object due to the fact that the Earth is rotating • Moving object travels in straight line from outside reference, but Earth has moved underneath, so object appears to move in a curved path • Objects are deflected to the RIGHT in the Northern Hemisphere and to the LEFT in the Southern Hemisphere • No effect at the Equator and maximum effect at the poles

  4. http://www.youtube.com/watch?v=mcPs_OdQOYU

  5. Global Winds • Winds named based on where they are coming from • Northern Hemisphere winds: • Polar Easteries • Prevailing Westerlies • NE Trade Winds • Southern Hemisphere winds: • Polar Easterlies • Prevailing Westerlies • SE Trade Winds

  6. Waves • Three main causes of ocean waves • 1. Wind* • 2. Tides • 3. Seismic Activity (earthquakes, volcanoes) • http://www.youtube.com/watch?v=dv_Sis0Hntk&feature=player_embedded • http://www.youtube.com/watch?feature=player_embedded&v=aXuQC1qRuEM

  7. Waves • Other factors affecting wave height • Distance from shoreline • Latitude • Water depth • Nearby landmasses

  8. Wave Energy • http://www.youtube.com/watch?v=7k5r89IseEM

  9. Tides • Definition – low, earth-wide waves that cause regular rise/fall in sea level • Take place every 12 hours and 25 minutes; therefore, they are predictable • Vary in height (from 1-20 meters)

  10. http://www.youtube.com/watch?v=6IyRE9azhwQ&feature=player_embedded#!http://www.youtube.com/watch?v=6IyRE9azhwQ&feature=player_embedded#!

  11. Causes of Tides 1. Gravity • Moon pulls water towards it, creates bulge on moon side of earth • Sun- same thing, but only about 1/3 – 1/2 the effect; responsible for extra high tides

  12. Causes of Tides 2. Inertia (centripetal force) • Things want to keep moving in straight line • “Counteracts” the force of gravity from moon • Causes opposite bulge on far side of earth

  13. Two high tides & two low tides per day • Time of high/low tide depends on the lunar cycle

  14. Types of Tides • Flood- when tide is coming in (change from a low to high tide) • Ebb- when tide is going out (change from a high to low tide) • http://oceanservice.noaa.gov/education/tutorial_tides/media/supp_tide01.html

  15. Types of Tides • Spring- very strong tides, due to alignment of Earth, sun, and moon (straight line) • Neap- very weak tides, due to alignment of Earth, sun, and moon at 90° angle (effects cancel) • http://oceanservice.noaa.gov/education/tutorial_tides/media/supp_tide06a.html

  16. Lunar Cycle- 29.5 days When would spring tides occur? When would neap tides occur?

  17. Lunar Cycle & Tides • Spring tides- new moon and full moon • Neap tides- 1st quarter moon and 3rd quarter moon • Spring & Neap occur once every 14 days • http://stardate.org/nightsky/moon

  18. http://oceanservice.noaa.gov/education/tutorial_tides/media/supp_tide05.htmlhttp://oceanservice.noaa.gov/education/tutorial_tides/media/supp_tide05.html

  19. Tidal Bore • Tidal bore occurs when a river runs backwards due to incoming tide and land formation around it

  20. Importance of Tides • Mix shallow waters • Move floating organisms into/from breeding areas • Fisheries, ships, recreation

  21. http://bayoffundy.com/about/highest-tides/

  22. Tsunamis • Tsunami- underwater seismic activity that transfers lots of energy into a water column • Ex.- Earthquakes, volcanoes, avalanches • Drawback- trough of wave reaches shore before the crest, so water along the shoreline recedes dramatically • Waves slow down as they reach the shore, increasing in height • http://upload.wikimedia.org/wikipedia/commons/2/2d/Propagation_du_tsunami_en_profondeur_variable.gif

  23. Tsunamis: Coastal Impacts • Not a huge breaking wave, rather a strong flood • Extreme destruction • Marine life washed ashore • Often injuries and casualties

  24. http://www.youtube.com/watch?v=BsRd7WQuBHc

  25. http://www.pbs.org/teachers/connect/resources/6723/preview/

  26. ENSO Cycle • ENSO (stands for El Niño/ Southern Oscillation) Cycle: • Year-to-year variations in temperature, rainfall, air pressure, circulation, etc. • Occurs in the equatorial Pacific • Highly irregular pattern • The cycle can last anywhere from 2-10 years

  27. El Niño • Refers to the above average sea-surface temperatures that periodically develop across the east-central equatorial Pacific • Represents the warm phase of the ENSO cycle • Cause: equatorial easterly trade winds diminish, resulting in an eastward shift of the Pacific warm pool

  28. How El Niño Affects Global Climate • Warmer winters across the northern U.S. • Gulf states cooler and wetter • Increases storms on the west coast of North & South Americas • Fisheries disrupted • Can cause a drought in Indonesia and western Pacific

  29. La Niña • Periodic cooling of sea-surface temperatures • East-central equatorial Pacific • Represents the cold phase of the ENSO cycle • Equatorial easterly trade winds strengthen

  30. How La Niña Affects Global Climate • La Niña has equally dramatic, often opposite effects of El Niño • Could increase the number of Atlantic hurricanes • Where there was drought, now turns to flooding; flooding turns to drought • Abnormally mild winter now turn to abnormally harsh winter

  31. 2011 La Niña • Major snowfall • Extreme flooding/high river levels • Severe drought in Southwest • Joplin/Tuscaloosa tornados • Warmer temperatures in the fall

  32. Tropical Cyclone • Huge rotating masses of low pressure • Generate strong winds and torrential rain • Called hurricanes in North and South America • Called typhoons in Pacific • Called cyclones in Indian Ocean

  33. Hurricane Conditions • Warm ocean water • Warm moist air • Coriolis Effect- causes hurricanes to spin • Found during late summer and early fall • Hurricane season: June 1- November 30

  34. Hurricane Movement • Driven by trade winds • Move east to west across oceans • Eye of the hurricane- winds are drawn upward, so horizontal wind speeds are low= usually calm • Composed of spiral rain bands that create intense rainfall • Movement over land cuts off energy source

  35. Hurricane Destruction • Caused by high winds and flooding from intense rainfall • Storm surge- extremely high winds cause water to pile up higher than normal sea level • Main cause of destruction

  36. Tropical Cyclone Destruction • Deadliest Storm: • Great Bhola Cyclone- 1970, Bangladesh killed 500,000 people • Top 30 deadliest tropical storms all occurred in Indian Ocean or western Pacific near China

  37. U.S. Hurricanes • Deadliest: • 1. Galveston Hurricane- 1900 in Galveston, TX killed over 6,000 people • Deadliest natural disaster in US history • 3. Hurricane Katrina- 1000 deaths • Most damaging: • Hurricane Katrina- 2005, caused over $100 billion in damage • Hurricane Sandy- 2012, caused $50 billion in damage

  38. http://www.youtube.com/watch?v=YeutC1WN6dc

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