期刊名称：Tellus A: Dynamic Meteorology and Oceanography
电子版ISSN：1600-0870
出版年度：2001
卷号：53
期号：5
页码：629-641
DOI：10.3402/tellusa.v53i5.12232
摘要：Making use of a simple two-layer model, we analyze the impact of freshwater forcing on thethermohaline circulation. We consider the forward-type circulation dominated by thermal forcing,implying that the freshwater forcing acts to reduce the density contrast associated withthe equator-to-pole temperature contrast (prescribed in the model). The system is described bytwo variables: the depth of the upper layer (H) and the density contrast between the upper and lower layer (∆p), which decreases with salinity contrast. The rate of poleward flow of lightsurface water and the diapycnal flow (i.e., upwelling) driven by widespread small-scale mixingare both modeled in terms of H and Dr. Steady states of thermohaline circulation are foundwhen these two flows are equal. The representation of the diapycnal flow (M D ) is instrumentalfor the dynamics of the system. We present equally plausible examples of a physically basedrepresentation of M D ) for which the thermohaline circulation either decreases or increases withdensity contrast. In the latter case, contrary to the traditional wisdom, the freshwater forcingamplifies the circulation and there exists a thermally dominated equilibrium for arbitrary intensityof freshwater forcing. Here, Stommel’s famous feedback between circulation and salinitycontrast is changed from a positive to a negative feedback. The interaction of such a freshwaterboosted thermohaline circulation with the climate system is fundamentally different from whatis commonly assumed, an issue which is briefly addressed.
