Monday, 12 May 2003: 2:30 PM
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This paper proposes a theory of climatic oscillation having a period consistent with observation of ice age periodicity. The creation and destruction of ice caps over both land and water is explained as an artifact of a natural cycle of the related creation and destruction of tropic-to-polar region ocean currents. The theory assumes a simplified earth-ocean model which absorbs a constant amount of solar radiation and re-radiates a constant amount of heat. The system therefore has a constant heat budget. Heat alternates between being concentrated in the tropic regions and being disbursed to the temperate/polar regions. When pole-bound currents are weak or absent, little heat is transferred out of the tropics. Localized solar heating results in an increasing depth of the thermocline in tropical regions. Corresponding cooling in the polar regions ultimately produces ice caps. Warm water is less dense than the cold water below the thermocline. As the depth of the thermocline in the tropics increases and the latitude at which the thermocline reaches the ocean surface decreases, the height of the water column in the tropics increases relative to that in the temperate and polar zones. Therefore, the gradient of ocean surface elevation increases. When the gradient is small, tropical surface water spreads gradually and fairly evenly toward higher latitudes. However, when the gradient becomes sufficiently large, it induces the creation of pole-bound currents at the western edges of the oceans. When the ice caps disappear and the latitude where the thermocline meet the ocean surface moves toward the poles, the ocean surface elevation gradient becomes small. Therefore, less water flows out of the tropics and the pole-bound currents collapse.
The model predicts a rising and lowering of the thermocline depth in the tropics on the same period as the occurrence of ice ages. It also predicts a rapid increase in surface temperature in high latitude temperate zones when water borne ice caps substantially disappear. The creation of pole-bound surface currents may be triggered by low frequency waves at the thermocline interface. Those low frequency sub-surface waves may also induce periodic increases in water flowing away from the tropics triggering the occurrence of an El Nino phenomenon.
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