Limitations of the streamtube model

A common feature of one-dimensional streamtube models is that the pressure gradient includes only the effect of the density difference between the plume and the ambient water on a sloping bottom. Variations of the streamtube height and density along the flow path are thus neglected. In the present paper a streamtube model is used to highlight the assumptions underlying the simplification and to obtain the limitations this prerequisite presents. The results indicate that the parameter range for which the simplification is applicable is largest when the initial outflow is parallel to the isobaths. More specific limits are given for three major outflows — the Mediterranean, the Faroe Bank Channel and the Denmark Strait outflow.