Interface Migration in Thermohaline Staircases

Abstract

Abstract A theory for the vertical migration speed (e) of interfaces within thermohaline staircases is developed and illustrated with several oceanic examples. It expresses e in terms of layer-to-layer variations in the vertical buoyancy flux (J). We discuss three mechanisms which can induce migration: 1) the nonlinearity of the equation of state; 2) layer-merging (the coalescence of adjacent layers); and 3) interface-splitting (the creation of new layers at the interfaces between existing layers), The theory predicts that migration will be much slower for nonlinearity than for layer-merging and inteface-splitting, because layer-merging and interface-splitting should lead to large O(1) variations in J, while nonlinearity leads to much smaller O(10−2) variations. Even so, the net effect of migration associated with layer-merging and interface-splitting should be small, since the interfaces will not have time to migrate very far before the staircase readjusts to a new, migration-free, equilibrium state. The...