Laboratory models of circulation in shallow seas

Abstract
Three laboratory experiments are described. The first was made to observe the flow field of circulation in a model given by Stommel & Leetmaa (1972). The experiment consisted of a very shallow (1 or 2 cm deep) annulus with an inner heated wall of radius 25 cm and a cooled outer wall of radius 57 cm, all mounted on a turntable. When the Ekman number was large the flow was steady and resembled the solutions for a non-rotating estuary given by Hansen & Rattray (1965), but when the Ekman number was small the flow became time-dependent. Values of shear and stratification obtained from theory indicate that the flowing water probably underwent baroclinic instability. It appears that such instability may develop on real shelves. The second experiment consisted of a shallow sea of constant depth bounded by a deep ocean through a uniformly sloping continental rise. The experiment is cooled from above and there is a region that exhibits sinking convection cells, which form the coldest water. This water then spills off the right-hand side of the shallow sea (looking downstream for counterclockwise rotation) and forms bottom water in the deep experimental ocean. The third experiment is a rotating version of the dam-break problem in which a density current is generated after a barrier has been removed. The rotation causes the current to lean against the right-hand wall (looking downstream for counterclockwise rotation) and turbulent eddies are detrained to the side rather than vertically.

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