Oceans - unit 3

• Earth's oceans cover 71% of Earth's crust
• Oceans make up 97% of water on Earth
• Major oceans

  • Pacific
  • Atlantic
  • Indian
  • Southern
• Pacific ocean


  Largest and deepest
• Atlantic ocean


  Larger than the Indian ocean
• Indian ocean


  Same depth as the Atlantic ocean but smaller
• Water on Earth came from volcanic activity, erosion from land, and waves breaking on the land
• Ocean water is a mixture of dissolved gases and solids in pure water
• Ocean water contains

  • 85-90 naturally existing elements
  • 96.5% pure water
  • 3.5% dissolved minerals
• Salinity


  Amount of dissolved salts in ocean water, expressed in ppt (parts per thousand) - number of grams of salts dissolved in 1 kg of ocean water
• Most common mineral in ocean water

  NaCl (sodium chloride)
• Salinity is usually the same, differences result from precipitation and runoff water from rivers being deposited into the ocean - results in lower salinity
• Freezing water in polar regions results in higher salinity
• Unusually high temperatures or below normal rainfall results in higher salinity
• Most abundant gases in ocean water

  • N2
  • CO2
  • O2
• Amount of gases in ocean water varies with depth, cold water holds more gases
• Processes affecting Salinity

  1. Decrease of Salinity: precipitation, runoff from land, icebergs melting, sea ice melting

  2. Increase of Salinity: evaporation, formation of sea ice
• Surface Currents

  • Movement of water in the ocean's surface, caused by friction between the ocean and the wind, created by the prevailing wind system, can be localized, seasonal, or permanent
• Gyres

  • Huge moving current systems that dominate the surface of the oceans, caused by the Coriolis effect, deflection of currents away from their origin due to Earth's rotation, different deflection directions in Northern and Southern Hemispheres
• 5 main gyres

  • North Pacific
  • South Pacific
  • Indian Ocean
  • North Atlantic
  • South Atlantic
• Major cause of gyres


  The Coriolis effect, the deflection of currents away from their origin as a result of Earth's rotation, deflection to the right in the Northern Hemisphere and to the left in the Southern Hemisphere
• Four main currents within each Gyre transfer heat from areas of high temperature to areas of low temperature
• Gulf Stream brings warmer water to Great Britain and Northwestern Europe, causing warmer winters
• Peru Current brings cooler water north to the tropics, causing cooler summers
• Ocean currents help maintain the Earth's heat balance, accounting for 25% of heat transport on Earth
• Upwelling


  Vertical rising of cooler ocean water to replace warmer surface waters, wind-induced, occurs along the western coast of continents, coastal winds and the Coriolis effect combine to move surface water away from the shore, cooler water from below moves upward to replace warm water resulting in cooler surface temperatures, bringing greater amounts of nutrients and marine life
• Ocean currents are caused by differences in temperature, salinity, wind patterns, and density.
• Warm water flows toward colder water because it has less mass per volume than cold water (less dense). This creates a horizontal pressure gradient force that drives the movement of water.
• Surface currents move horizontally along the ocean's surface, while deep-water currents flow vertically through the water column.
• Factors affecting density - salinity and temperature
• Pycnocline - a layer of ocean water between 300 -1000m where there is a rapid change in density with depth
• Thermocline - layer of ocean water between 300 -1000m, rapid change in temperature with depth
• Forces Acting on the Shoreline


  • Wave impact
  • Porosson
  • Refraction
  • Longshore Currents
• Wave impact

  Water against the shoreline
• Porosson
• Refraction
• Longshore Currents
• Erosional Features

  • Wave Cut Cliffs
  • Wave Cut Platform
  • Sea Arches
  • Sea Stacks
• Wave Cut Cliffs

  Caused by waves cutting action
• Wave Cut Platform

  Beach-like surface left behind by receding cliff