Mechanisms and Toy Models of the Glacial Cycles

A laboratory experiment has been conducted in which a small basin was heatedfrom below. This basin was connected to a large reservoir that was filled with a layerof salt water at the bottom and fresh water above it, by tubes at the top, the middleand the bottom. It was shown that different flow regimes exist in this experiment. Forlow forcing temperatures, self-sustained oscillations occur, whereas the system reaches asteady state with deep convection for higher forcing temperatures. During an oscillationa shallow convecting layer of salty water at the bottom of the basin grows and entrainsfresh water, until the water column becomes unstable and deep convection can occur.Inflow of salty water through the bottom tube stops the deep convection and the cyclestarts again. In a configuration in which the top and middle tubes had smaller diameters,no oscillations were found. Instead, a regime with steady shallow convection states anda regime with steady deep convection states were found.