Ocean Currents: Comprehensive Notes

Ocean Currents

Overview

• Ocean currents are continuous movements of water in the Earth's oceans.
• Factors influencing ocean currents:
  • Wind
  • Tides
  • Density
  • Earth’s rotation

Circulation

• Surface Currents:
  • Circulation is driven by wind.
    • Near the shore: wind and tide.
    • Open ocean: wind.
• Deep Ocean Currents:
  • Circulation is largely driven by water density or thermohaline.
    • Temperature (thermo/heat)
    • Salinity (haline/salt)

Current Levels

• Surface Currents:
  • Currents are produced at a 90° angle to its direction due to Earth’s rotation (Coriolis effect).
    • Northern Hemisphere: to the right.
    • Southern Hemisphere: to the left.
  • Consequence:
    • Diverging currents cause upwelling.
    • Converging currents cause downwelling.
• Deep Ocean Currents:
  • Circulation is slow and generates weak currents due to the density of the water.
  • Both temperatures and salinity affect the density of water:
    • The colder the water is, the more dense it is.
    • The saltier the water is, the more dense it is.
    • The more dense the water, the deeper it goes.

Results

• Surface Currents:
  • Gyres occur, which are circular loops or spiral oceanic surface currents found in both the Northern and Southern Hemispheres.
  • Coriolis effect: the principle behind the surface current circulation where the wind push the water in the same rotating gyres.
  • Temperature and salinity of water are affected by precipitation, evaporation, and river runoff.
• Deep Ocean Currents:
  • Thermohaline circulation is the principle behind the deep ocean circulation where deep-ocean currents are driven by differences in the water’s density, which is controlled by temperature (thermo) and salinity (haline).
  • Gyres
  • Whirlpools
• The Global Conveyor Belt