A systematic approach to determine thresholds of the ocean's thermohaline
circulation
Dijkstra, H. A., L. te Raa and W. Weijer, 2004.
Tellus, 56A, 362-370.
A systematic approach is proposed to determine thresholds in freshwater flux perturbations related to abrupt changes in the ocean's thermohaline circulation. The typical problem considered is the response of the thermohaline driven flow to a localized change, of specified strength and duration, in the surface freshwater flux. The initial response due to the freshwater anomaly is considered as a finite amplitude perturbation. An estimate of this response can be obtained by using ideas from dynamical systems theory. Central quantity to determine whether such a perturbation leads to instability (i.e. a `collapsed' state) is the sign of the tendency of a specific energy functional. The approach is first illustrated with a simple box model and then shown to give good results in a global ocean general circulation model. Full text (pdf)