Topic: Currents and Ocean Circulation
Theme: Interactions

Key Concepts

El Niño

Thermohaline Circulation

Currents and Ice Ages

Currents and Shipping Lanes

  • The icebergs that drift southward past Newfoundland to become hazards in the shipping lanes of the Northrn Atlantic nearly always start as glaciers on Greenland's west coast.
    • Great blocks of ice break off the glacier in a process known as "calving."
    • Wind and currents permitting, these blocks of ice drift into Baffin Bay.
    • Each year an estimated 10,000 icebergs are manufactured by Greenland's west coast glaciers.
    • Icebergs hitch a ride on the West Greenland Current and drift southward in the Labrador Current.
    • Less than 500 of the 10,000 icebergs make it into the open seas.
    • Large icebergs--like the 60-foot berg that sunk the Titanic--can still travel long distances, propelled by vigorous currents and steady wind.

Currents and the Seafloor

  • Hurricane generated currents cause coastal erosion.
  • Storm Surges created by tropical hurricanes/cyclones can develop domes of water only a meter high in the ocean. As they approach the shallow water of the bay or coastal area, they increase in height. Some can reach heights of 12 meters
    • A storm surge is not a wave. It is only a crest with no wavelength or period. It rushes inland in what looks like a suddent wind-blown tide.
    • Storm surges can have catastrophic consequences
      • Bangladesh in 1970 - more than 300,000 deaths
      • Dutch Coast in 1953 - 1,783 deaths
      • Galveston, TX in 1900 - 6,000 deaths
  • Turbidity currents (which occur underwater) are like avalanches. They can carry large quantities of sediment down continental slopes and onto the abyssal plains.
    • Turbidity currents can be triggered by disturbances such as earthquake vibrations, sudden large discharges of sediment by rivers, and coastal storms in the same way avalances on continents can be triggered by noises or storm winds.
    • Since turbidity currents flow down submarine canyons, the scouring action creates and maintain the canyons.