motion in ocean

• Ocean currents


  Movements of water from one region to another, often over long distances and time periods
• Forces acting upon the water to generate currents

  • Earth's rotation
  • Wind
  • Temperature differences
  • Salinity differences
  • Gravitation of the moon
• Ocean


  • Covers 71 percent of the planet and holds 97 percent of its water
  • Key factor in the storage and transfer of heat energy across the globe
  • Movement of heat through local and global ocean currents affects the regulation of local weather conditions and temperature extremes and stabilization of global climate patterns
  • Important for transporting salts, nutrients and marine creatures
  • Knowledge of currents is vital for navigation, shipping, search and rescue and the dispersal of pollutants
• Factors that affect direction of currents

  • Earth's rotation
  • Shape of the sea floor
  • Water temperature
  • Salinity levels
  • The wind
• Coriolis Effect


  • The rotation of the Earth causes an interesting phenomenon on free moving objects on the Earth e.g. wind and ocean currents
  • Wind and Ocean Currents in the Northern Hemisphere are deflected to the right, while objects in the Southern Hemisphere are deflected to the left
• Types of currents


  • Surface currents
  • Deep water currents
• Surface currents


  • The top 400 metres of the ocean's surface is moved primarily by winds that blow in certain patterns because of the Earth's spin and the Coriolis Effect
  • These currents flow in a regular pattern but they can vary in depth, width and speed
  • The Coriolis Effect deflects currents into circular patterns called gyres
• Gyres


  Swirling circular ocean currents – clockwise in the Northern Hemisphere and anti-clockwise in the Southern Hemisphere
• Deep water currents


  • Also known as the Global Conveyor Belt
  • Driven by thermocline circulation
  • Thermocline Circulation refers to the flow of ocean water caused by changes in water density e.g. salt & temperature levels can change
  • Deep water currents make up about 90 per cent of water movements in the ocean
  • Surface currents make up the remaining 10 per cent
• Global Ocean Conveyor Belt

  1. Warm water which holds less salt and is less dense than cold water, travels from the equator near the surface into higher latitudes

  2. When the warm water surfaces it loses some of its heat

  3. It then mixes with Colder Artic waters and becomes cold, salty water. This is more dense and sinks, flowing as a deep current

  4. This creates a continual looping current which moves at a rate of 10cm/s and may take up to 1000 years to complete one loop

  5. The quantity of water moved in the Global Conveyer Belt is more than 16 times the water volume of all the world's rivers
• Upwellings


  • The movement of cold water currents from the deep sea to the surface
  • This occurs in very productive fishing grounds as the upwellings brings nutrients from the seabed which provide food for the growth of plankton, often the start of marine food chains
• Upwelling currents


  • Whale sharks gathering in the tropical waters of the Gulf of Tadjoura off the coast of Djibouti (Africa) to feast on prolific plankton blooms induced by oceanographic upwelling
• Downwellings


  • When currents sink taking with them oxygen and carbon dioxide from the atmosphere
  • These currents stir up the water and help distribute heat, gases and nutrients
• Main ocean gyres


  • South Pacific Gyre
  • Indian Ocean Gyre
  • South Atlantic Gyre
  • North Pacific Gyre
  • North Atlantic Gyre