Ocean circulation

Surface Layer (top 1 km)

  1. Surface currents depend on
    • average surface winds (trade winds,etc)
    • Solar heating
    • Coriolis effect (Eckman spirals -icebergs move at 90° to wind direction)
    • Gravity
  2. Forms gyres - large circular currents (rhymes with tire).
  3. Clockwise (CW) gyres in the northern hemisphere oceans.
  4. CCW gyres in the southern hemisphere.
  5. Surface currents very complex (eddies, rings, convergence/divergence, geostrophic currents)
  6. Research ongoing for short-term variations (ENSO, NAO, PDO).

Deep Ocean layers

  1. Currents form as a result of thermohaline effects = colder, more saline water sinks.
  2. Temperature differences are low (< 4°C)
  3. Weak currents but HUGE volumes.

The Great Conveyor

  1. Surface and deep currents combined.
  2. Very complex and still far from understood.
  3. Transport times are long = centuries to 1400 years.
  4. Important impact on Earth's heat budget. 2000 x 1012 watts northward in Atlantic.
  5. Important component of Earth's carbon budget (CO2).
    • Oceans hold 50x more carbon than land or air reservoirs.
    • Cold water dissolves more gases.
    • Increasing temp of ocean or increasing turnover of deep water could have HUGE effect on atmospheric CO2.