Lecture on Ocean Currents

Introduction to Ocean Currents

• Ocean currents provide insight into rotation and direction, influenced by continents.
• Example: 1990 container ship accident with Nike shoes and rubber toys helped understand current directions.

Major Ocean Currents

• Gyres:
  • Rotate clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.
  • Influenced by the Earth's rotation.
• Alaska Current:
  • Moves away from coastlines, causing upwelling.
  • Brings nutrients from deeper waters, supporting high productivity and fisheries.
  • Alaska region is a major fishery area.

Interaction with Atmosphere

• El Niño Events:
  • Affect climate and trade winds, reducing upwelling.
  • Impact on Galapagos iguanas' diet and survival adaptations.

Measuring Ocean Currents

• Use instruments and satellite data.
• Atlantic Ocean Currents:
  • Influenced by northeast and southeast trade winds.
  • Water veers right of the winds in the Northern Hemisphere, left in the Southern Hemisphere.
  • Leads to formation of surface gyres and westward intensification.

Antarctic Circumpolar Current

• Largest surface water flow around Antarctica.
• East and West Wind Drifts:
  • East Wind Drift moves west, West Wind Drift moves east.
  • Unimpeded due to Antarctica's separation from other continents.

Upwelling and Downwelling

• Upwelling:
  • Occurs when water moves away from coastlines, bringing nutrients to the surface.
• Downwelling:
  • Happens where currents converge, aiding oxygen transport to deeper oceans.

Gulf Stream

• Fast-moving current from the equator to higher latitudes.
• Transfers heat, affecting climates like Great Britain.
• Not a linear current; contains eddies that impact navigation.

El Niño and La Niña

• El Niño:
  • Causes climatic shifts, impacting fisheries and precipitation.
• La Niña:
  • More intense upwelling conditions following El Niño.

Deep Water Currents

• North Atlantic Deep Water (NADW):
  • Cold and dense, sinks around Greenland and Labrador.
  • Carries oxygen to deeper ocean layers.
• Antarctic Bottom Water:
  • Coldest, densest deep water current.

Thermohaline Circulation

• Global ocean circulation involving sinking and surface currents.
• Takes about 1000 years for a water molecule to complete the cycle.
• Important for distributing heat globally.

Summary

• Main gyres and currents discussed.
• Upcoming topics: waves, tides, coastal waters, and ocean productivity.

Notes compiled from the lecture on ocean currents, focusing on their behavior, measurement, and global impact.