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Ice Drilling Program

School of Ice

Thermohaline Circulation Demonstrations

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www.icedrill-education.org

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Thermohaline Circulation Demonstrations

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Part-1 Salinity

  • Prep:
  • Two large cylinders, one filled with fresh water, one filled with saturated salt water.
  • Do not reveal which is fresh, which is salt.
  • Two large ice cubes (or frozen cups or small balloons)
  • If possible, color ice cubes blue. Alternative is to add 2-3 drops of food color on top of the ice cubes after putting into the cylinder.

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Thermohaline Circulation Demonstrations

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Part-1 Salinity

  • Teaching set-up:
  • Ice cubes will be added to each… which cylinder will result in the ice cube melting faster, the salt water or the fresh water?
  • Add the ice cubes, observe, come back to the demo later after ice has melted.

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Thermohaline Circulation Demonstrations

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Part-1 Salinity

  • Processing
  • Now which tube do you think contained the salt water?
  • Salt water is non-mixed tube on the left. Fresh water is less dense as it melts in the salt water, forms a capping layer, inhibits circulation.
  • Fresh water runoff from Greenland is forming a fresh capping layer on the ocean that is inhibiting the circulation in the North Atlantic.

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Thermohaline Circulation Demonstrations

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Part-2 Temperature

  • Prep:
  • Four 125mL or 250mL Erlenmeyer flasks.
  • Warm-Hot water (red) and cold water (blue)
  • Place a square of notecard over the flask and invert.

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Thermohaline Circulation Demonstrations

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Part-2 Temperature

  • Teaching set-up:
  • What are some things that might happen when the notecards are pulled out from between the hot and cold water samples?

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Thermohaline Circulation Demonstrations

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Part-2 Temperature

  • Processing
  • Flasks with hot water on top stay in place without the notecard.
  • Flasks with cold water on top circulate immediately.
  • Cold water is more dense than warm water. As North Atlantic warms, there is a smaller temperature gradient between the cold surface waters and the warmer deep water. This decreasing gradient causes less vigorous sinking/circulation.