ocean currents
Skip this Video
Download Presentation
Ocean Currents

Loading in 2 Seconds...

play fullscreen
1 / 31

Ocean Currents - PowerPoint PPT Presentation

  • Uploaded on

Ocean Currents . Earth Science . Ocean Currents . Currents- water in a stream Surface currents- currents that move on or near the surface & are caused by wind Deep current- move very slowly beneath the surface of the ocean & are caused by density differences in water .

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about ' Ocean Currents ' - graham

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
ocean currents

Ocean Currents

Earth Science

ocean currents1
Ocean Currents
  • Currents- water in a stream
    • Surface currents- currents that move on or near the surface & are caused by wind
    • Deep current- move very slowly beneath the surface of the ocean & are caused by density differences in water
ocean currents surface currents
Ocean Currents: Surface Currents
  • Driving energy source for surface currents is wind
  • Surface currents extend down to a depth of 100m
  • 3 controlling factors in surface currents
    • Wind belts
    • Earth’s rotational effects
    • Location of the continents
ocean currents surface currents1
Ocean Currents: Surface Currents
  • Wind belts
    • Most directly affect the surface currents
    • Trade winds & westerlies
      • Trade winds at latitudes north & south of the equator
      • Westerlies are located in the middle latitudes
      • North of the equator the trade winds blow from the northeast (Northern Hemisphere) & are usually warm
      • Southern Hemisphere trade winds blow from the south east
        • In both hemispheres they push water to the west

Wind Belts

    • Northern Hemisphere westerlies blow from the southwest…moves currents eastward across the Atlantic & Pacific Oceans
    • Southern Hemisphere westerlies blow from the northwest…moves currents eastward
      • Produce the largest current on earth…West Wind Drift
        • Travels the entire circumference of the earth and is located in the southern part of all 3 major oceans
ocean currents surface currents2
Ocean Currents: Surface Currents
  • Coriolis Effect
    • Deflection of the earth’s winds and ocean currents based on the rotation of earth
    • Coriolis effect along with the earth’s winds cause gyres
      • Gyres- huge circle of moving water
      • Northern hemisphere- gyre moves clockwise
      • Southern hemisphere- gyre moves counterclockwise
ocean currents surface currents3
Ocean Currents: Surface Currents
  • Continents
    • The surface current flows against a landmass and is divided and deflected
  • Equatorial Current
    • Warm currents
    • 2 of them both move in a westward direction
ocean currents surface currents4
Ocean Currents: Surface Currents
  • North Pacific & Atlantic Currents
    • North Atlantic
      • North Atlantic Equatorial Current
        • Warm current that moves water north along the east coast of North America called the Gulf Stream
        • Gulf Stream widens & slows and becomes the North Atlantic Drift
          • Drift- weak current
        • All of those currents form the North Atlantic Gyre
ocean current surface currents
Ocean Current: Surface Currents
  • North Pacific
    • Similar to the North Atlantic
    • Japan Current is equivalent to the Gulf Stream
      • Flows northward & turns into the North Pacific Drift when it spreads out & slows down as it flows towards North America
ocean currents surface currents5
Ocean Currents: Surface Currents
  • Currents in the Southern Hemisphere
    • Currents here also flow in gyres but in a counterclockwise direction
    • Southern regions of all three major oceans constant westward winds produce the West Wind Drift
      • West Wind Drift is the largest current in the world
      • Because there is no continents to stop it the West wind drift completely circles Antarctica
ocean currents surface currents6
Ocean Currents: Surface Currents
  • Currents in the Southern Hemisphere cont…
    • Indian Ocean currents follow 2 patterns
      • Southern part the currents follow a counterclockwise gyre
      • Northern part the currents are governed by monsoons
        • Monsoons change directions with the seasons
ocean currents deep currents
Ocean Currents: Deep Currents
  • Cold, dense currents that flow beneath the surface of the ocean
    • Much slower moving than surface currents
  • Produced as cold, dense water of the polar regions sinks & flows beneath warmer ocean water toward the equator
    • Movements are the result of density differences
    • Higher density of polar waters is also a result of an increase in salinity
  • Deep-current layer rises only when winds blow the surface water out of the way
ocean currents deep currents1
Ocean Currents: Deep Currents
  • Antarctic Bottom Water
    • The densest & coldest ocean water in the world
    • Dense, cold water sinks to the bottom & very slowly move north forming the Antarctic Bottom Water current
      • Moves to north to about 40 degrees & takes several hundred years to make the trip
ocean currents deep currents2
Ocean Currents: Deep Currents
  • North Atlantic Deep Water
    • South of Greenland the water is exceptionally cold & has high salinity causing it to sink
      • Forms a current that travels south underneath the Gulf Stream
      • Flows southward all the way to the Antarctic & over the Antarctic Bottom Water
    • Deep Atlantic currents also are found near the Mediterranean Sea
ocean currents deep currents3
Ocean Currents: Deep Currents
  • Turbidity Currents
    • Occur when large masses of sediment that have accumulated along a continental shelf or continental slope suddenly break loose and slide downward
      • Causes the water to become more dense than the surrounding water
      • Believed to cause submarine canyons to deepen
ocean waves
Ocean Waves
  • Wave- periodic up and down movement of water
    • Transfer energy
  • 2 basic parts of a wave:
    • Crest- highest point of a wave
    • Trough- lowest point of a wave
  • Wave characteristics
    • Wave height- vertical distance between a crest & a trough of a wave
    • Wavelength- horizontal distance between 2 crests of a wave
    • Wave period- time it takes for one complete wavelength
    • Wave speed= wavelength/period
ocean waves1
Ocean Waves
  • Wave Energy
    • Main source of energy for waves is wind
      • The more energy that is transferred the larger the wave becomes
    • Because of surface area…
      • Large waves tend to become larger because the wind has more area to push on
      • Smaller waves tend to die out because there is a very small surface area for the wind to push on
    • Swell- group of long, rolling waves that are the same size
ocean waves2
Ocean Waves
  • Water Movement in A Wave
    • Only the energy of wave moves forward, the water itself moves very little
      • The water particles within the wave move in a circular motion
        • Circle traced by each water particle in a wave has a diameter equal to the height of the wave
    • Energy received by a wave decreases as depth increases because the waves receive their energy from the wind
      • Diameter of the circle traced by each water particle decreases as depth increases
ocean waves3
Ocean Waves
  • Wave Size
    • 3 factors that affect wave size:
      • Speed of the wind
      • Length of time the wind blows
      • Fetch of a wave
        • Distance that the wind can blow across open water
        • Long fetch produces very large waves
          • Likely to occur during storms
    • Size of a wave will only increase to a certain height to length ratio before it collapses
    • Whitecaps- occur when high wind speeds blow the crest off of a wave
ocean waves waves the shore
Ocean Waves: Waves & the Shore
  • Breakers
    • Height of a wave changes as the wave approaches the shore
    • As a wave moves into shallow water, the bottom of the wave is slowed by friction but the top of the wave continues to move at its original speed
    • The top of wave gets farther & farther ahead of the bottom & eventually it topples over & forms a breaker.
      • Height of the wave when it topples over is one to two time the height of the original wave
ocean waves waves the shore1
Ocean Waves: Waves & the Shore
  • Breakers cont…
    • Size & force of breakers are determined:
      • Original wave height
      • Wavelength
      • Steepness of the ocean floor close to shore
        • More steep = rapid increase of wave height = breaker with greater force
          • Pacific Coast
        • Less steep = slower increase of wave height = breaker with less force
          • Atlantic Coast
ocean waves waves the shore2
Ocean Waves: Waves & the Shore
  • Undertows & Rip Currents
    • Undertow- water carried onto a beach is pulled back into deeper water by an irregular current
      • Create problems only along shores with steep drop-offs
    • Rip current- form when water from large breakers returns to the ocean through channels in underwater sand bars that are parallel to the beach
      • Flow perpendicular to shore
ocean waves waves the shore3
Ocean Waves: Waves & the Shore
  • Longshore Currents
    • Form sandbars
    • Forms as waves approach the beach at an angle
    • Flow parallel to the shore
ocean waves wave the shore
Ocean Waves: Wave & the Shore
  • Tsunamis
    • Most destructive waves in the ocean
    • Energy that forms them comes from seismic sea waves not the wind
      • Usually caused by earthquakes on the ocean floor, but also by volcanic eruptions & underwater landslides
    • Have very long wavelength, wave period is about 15 minutes, and speed of 725 km/hr
    • Entire depth of the water is involved in wave motion
    • Height increase greatly as they approach shore
  • Tides- daily changes in the level of the ocean surface
    • The gravitational pull of the moon on the earth and its waters is the major cause of tides
    • Low tides are formed halfway between two high tides
tides behavior
Tides: Behavior
  • Tidal movement is due to the rotation of the earth and the pull of the moon.
    • Earth rotates from west to east, so tidal bulges appear to move westward around the earth.
      • Because there are two tidal bulges most locations on the ocean have two high tides & two low tides
    • Tidal range- difference in the level of high tide and low tide at specific locations
      • Can vary widely from place to place
tides behavior1
Tides: Behavior
  • During period of new moon & full moon the high tides are the highest and the low tides the lowest
    • This is because the sun, moon, & earth are all aligned
    • These are called spring tides
  • During 1st quarter & 3rd quarter phases the daily tidal range is the smallest
    • This is because the moon & the sun are at right angles to each other in relation to the earth
    • These tides are called neap tides
tides variations
Tides: Variations
  • Tidal patterns are greatly influenced by the size, shape, depth, & location.
    • Atlantic Coast: tides are semidiurnal, which means twice a day
      • Have a fairly regular tidal range
    • Gulf of Mexico: diurnal, which means once a daily
    • Pacific Coast: follow a mixed pattern & have an irregular tidal range
      • Very high followed by very low, then a lower high tide followed by a higher low tide
tides variations1
Tides: Variations
  • Tidal oscillations- caused by the slow rocking motions of ocean water that occur as the tidal bulges move around the ocean basins
    • Produce the world’s greatest tidal range in the Bay of Fundy (tidal ranges is larger than 15m)
tides tidal currents
Tides: Tidal Currents
  • Tidal current- occurs as the ocean water rises and falls with the tides, it flows toward & away from the coast.
    • Flood tide- when tidal current flows toward the coast
    • Ebb tide- when tidal current flows away from the coast
    • Slack water- time between flood tide and ebb tide with no tidal currents.
  • Tidal bore- surge of water that rushes upstream where a river meets an ocean
tide videos
Tide Videos
  • http://youtu.be/kJOvxQElfLc
  • http://youtu.be/5W2sM1Ma7YA