Topographic control of rotating deep water flow through the combination ofa sill and a horizontal constriction

Many subsurface passages connecting the deep parts of the oceans have a top ography such that the location of the most pronounced horizontal constricti on does not coincide with that of the sill. When applying rotating hydrauli c theory to describe the deep water flow through channels of this type, a p roblematic situation emerges since the standard analysis assumes a well-def ined controlling section. The present study demonstrates how the associated critical flow problem arising from the hydraulic model may be resolved on the basis of functional-theoretical analysis. The methodology is applied to the deep water flow into the Baltic proper through the Bornholm Channel, w here multiple critical cross sections were found. These, as well as the ass ociated critical transport predictions, are discussed, and it is found that only one of them serves de facto as a control with unidirectional flow.