Ocean currents: coastal processes

• what are the sources of ocean currents

  tidal rise and fall, winds and thermohaline circulation
• what us thermohaline circulation


  within the oceans works to redistribute heat around the world
• what are ocean currents

  - near the poles water is chilled (/frozen). It also gets saltier because as ice is formed more salt is left in the ocean

  - this cold slaty water is denser and sinks. As it sinks, surface water moves in to replace it, creating a current

  - the dense cold water moves down towards the equator when it's warmer and then moves back up towards poles.
• what are longshore currents (caused by wind)

  - waves don't approach beach perfectly parallel to shoreline. rather they arrive at slight angle, called 'angle of wave approach'

  - when wave reaches beach/coastline, it releases bursts of energy that generates a current, which runs parallel to shoreline

  - this type of current is called a 'longshore current
• what is upwelling (caused by wind)

  - wind blows across ocean surface pushes water away from an area

  - when this occurs, water rises up from beneath the surface to replace the diverging surface water

  - this process is known as upwelling
• what is downwelling


  - wind blows over the surface of the ocean

  - often along coastlines and areas where surface waters converge as it forces water into a smaller space, causing it to sink.

  - the surface water sinks towards bottom, bringing dissolved oxygen and nutrients into the deeper ocean layers (supports marine life)
• What is an example of downwelling

  The North Atlantic Ocean.

  - warm water from the Gulf Stream cools and sinks, forming part of a significant ocean conveyor belt called the Thermohaline Circulation.