关键词: 热盐环流, 平衡响应, 瞬变响应

Abstract: The equilibrium response of the thermohaline circulation (THC) to changes of atmospheric Green House Gases is simulated using a fully coupled climate model. The strength of the North Atlantic THC decreases about 20% when the concentration of atmospheric CO₂ doubles and increases about 13% when the concentration halves. The response of the THC is divided into two different stages: the transient stage and the equilibrium stage. The transient response is mainly attributable to the changes of local surface heat flux and freshwater flux in the high latitude of North Atlantic, while the equilibrium response is also relevant to the non-local transport of heat and freshwater by THC itself, with the former acting as a positive feedback and the later as a negative feedback. The slow recovery of THC in the doubled CO₂ experiment implies the role of the positive feedback overwhelms that of negative feedback, while the equilibrium behavior of THC in the halved CO₂ experiment suggests that they cancel each other. In addition, the nonlinear relationship between density and temperature of seawater leads to the nonlinear behavior of the THC responses in doubled and halved CO₂ experiments.

Key words: thermohaline circulation, equilibrium response, transient response