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The Dynamic Ocean

The Dynamic Ocean. The Dynamic Ocean. Surface Circulation Deep-Ocean Circulation Shorelines & Shoreline Features Waves & Wave Erosion U.S. Coastal Problems Tides. Terms. Gyre A circular pattern of connected surface currents Tides Daily rise and fall of shorelines around the world ocean

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The Dynamic Ocean

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  1. The Dynamic Ocean

  2. The Dynamic Ocean • Surface Circulation • Deep-Ocean Circulation • Shorelines & Shoreline Features • Waves & Wave Erosion • U.S. Coastal Problems • Tides

  3. Terms • Gyre • A circular pattern of connected surface currents • Tides • Daily rise and fall of shorelines around the world ocean • Tidal range • Difference in height between high and low tide

  4. Surface Circulation PSCI 131: The Dynamic Ocean

  5. Surface Circulation PSCI 131: The Dynamic Ocean • Surface ocean currents are “rivers” with very different temperature and density than surrounding water • Driven by wind blowing across ocean surface • Ultimate energy source: Sun • Carry warm water from tropics to poles and vice versa

  6. Surface Current Patterns PSCI 131: The Dynamic Ocean: Surface Circulation

  7. Influence on Climate: The Gulf Stream PSCI 131: The Dynamic Ocean: Surface Circulation • Moves warm water north from tropics • Gives British Isles a temperate climate North America Water movement

  8. Upwelling PSCI 131: The Dynamic Ocean: Surface Circulation • Vertical movement of water • Deeper water moves up to replace surface water moved away by winds • Depths: 150-1,000 feet • Replenishes nutrients

  9. Upwelling PSCI 131: The Dynamic Ocean: Surface Circulation • Upwelling along African coast

  10. Deep-Ocean Circulation PSCI 131: The Dynamic Ocean

  11. Deep-Ocean Circulation PSCI 131: The Dynamic Ocean • Much deeper than surface circulation or upwelling – can affect ocean floor • Vertical motion driven by density differences • If upper layers become denser, they sink • Density controlled by temperature and salinity • aka “thermohaline” circulation

  12. Deep-Ocean Circulation PSCI 131: The Dynamic Ocean Cold, dense surface water in polar regions sinks, driving deep-ocean circulation

  13. Shorelines & Shoreline Features PSCI 131: The Dynamic Ocean

  14. Shoreline: Terminology PSCI 131: The Dynamic Ocean: Shorelines • Shoreline: contact between water and land • Coast: area from shoreline inland as far as ocean-related features are found • Coastline

  15. Shoreline: Terminology PSCI 131: The Dynamic Ocean: Shorelines • Coastline: Highest line affected by storm waves

  16. PSCI 131: The Dynamic Ocean: Shorelines: Terminology • Shore: low tide line to coastline • Foreshore: low tide line to high tide line • Backshore: high tide line to coastline

  17. PSCI 131: The Dynamic Ocean: Shorelines: Terminology • Nearshore: surf line to low tide line • Offshore: beyond surf line

  18. Shoreline Features: Beaches PSCI 131: The Dynamic Ocean: Shorelines • Accumulations of sediment along margin of ocean or lake • Berm: level area, usually dry • Beach face: sloping area, usually wet • Berm:

  19. Shoreline Features: Beaches PSCI 131: The Dynamic Ocean: Shorelines • Composition: any locally available sediment type • Quartz sand • Shells • Volcanic material • Etc. Rocky Great Lakes beach Shells Black volcanic sand

  20. Shoreline Features: Barrier islands PSCI 131: The Dynamic Ocean: Shorelines • Wide beaches • Separated from mainland by marshes or narrow seaways • Shaped by wave erosion and storms Wave-cut cliff (uplifted wave-cut platform)

  21. Shoreline Features: Cliffs, Platforms, Terraces PSCI 131: The Dynamic Ocean: Shorelines Wave-cut cliff (uplifted wave-cut platform)

  22. Shoreline Features: Sea Arches and Sea Stacks PSCI 131: The Dynamic Ocean: Shorelines

  23. Shoreline Features: Spits, Bars, Tombolos PSCI 131: The Dynamic Ocean: Shorelines

  24. Changing Shoreline Features Along Irregular Coastlines PSCI 131: The Dynamic Ocean: Shorelines

  25. Changing Shoreline Features Along Irregular Coastlines PSCI 131: The Dynamic Ocean: Shorelines

  26. Evolving Shoreline Features Along Irregular Coastlines PSCI 131: The Dynamic Ocean: Shorelines

  27. Waves and Wave Erosion PSCI 131: The Dynamic Ocean

  28. Ocean Waves PSCI 131: The Dynamic Ocean: Waves & Wave Erosion • Created by wind • Energy propagating along water-air boundary • Waves move differently in deep and shallow ocean • Deep: no net movement of water, circular motion • Shallow: water is displaced, linear motion

  29. Ocean Waves PSCI 131: The Dynamic Ocean: Waves & Wave Erosion Wave base Wave base: depth below which water does not “feel” wave Wave base = ½ wavelength

  30. Deep ocean wave motion is circular PSCI 131: The Dynamic Ocean: Waves & Wave Erosion 1 5 2 6 3 7 8 4 Boat returns to starting position

  31. Shallow ocean wave movement PSCI 131: The Dynamic Ocean: Waves & Wave Erosion Wave base

  32. Wave Erosion PSCI 131: The Dynamic Ocean: Waves & Wave Erosion • Direct impact of water • Abrasion by sediment in the water Rocks polished by abrasion Cliff undercut by wave impacts

  33. Shoreline Sediment Movement PSCI 131: The Dynamic Ocean: Waves & Wave Erosion • Longshore transport • Beach drift • Longshore currents

  34. U.S. Coastal Problems PSCI 131: The Dynamic Ocean

  35. Pacific Coast PSCI 131: The Dynamic Ocean: U.S. Coastal Problems • Emergent:Steep, geologically active, rugged • Cliffs with narrow beaches • Beaches are getting narrower • Natural sand supplies from rivers have been restricted by damming • Since beaches absorb wave energy, narrower beaches means faster wave erosion of cliffs

  36. Atlantic and Gulf Coasts PSCI 131: The Dynamic Ocean: U.S. Coastal Problems • Submergent: Flat, geologically quiet • Wide beaches, barrier islands • Rising sea level is causing more frequent flooding • Gentle slope of coastline amplifies effect of sea level rise • Wetlands and barrier islands • Natural protection for mainland from storms • Draining and development is diminishing this protection Gulf Coast wetlands

  37. Tides PSCI 131: The Dynamic Ocean

  38. PSCI 131: The Dynamic Ocean: Tides Tides are caused by Moon’s gravity (and Sun’s to a lesser extent) Moon’s gravity pulls harder on side closer to Moon, creating bulges of ocean water on opposite sides of Earth Bulges are always aligned with Moon, and Earth rotates through them Tidal bulge animation

  39. Monthly Tidal Cycle PSCI 131: The Dynamic Ocean: Tides Spring tide: Lunar and solar gravity work together to produce largest tidal range twice per month

  40. Monthly Tidal Cycle PSCI 131: The Dynamic Ocean: Tides Neap tide: Lunar and solar gravity work against each other to produce smallest tidal ranges twice per month

  41. End of Chapter

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