SIMULATION OF ABRUPT CLIMATE EVENTS IN HOLOCENE WITH AN EARTH-SYSTEM MODEL OF INTERMEDIATE COMPLEXITY
基于中等复杂地球系统模式的全新世 气候突变事件模拟试验*

Abrupt climate change events used to be happening on the wet and warm climate background of Holocene, for example, those happened at about 8.2kaB.P. and 4.2kaB.P. when the climate jumped into dry and cold states. Ocean circulation is considered as a key part in these events to amplify and transfer climate signals. Scientists have applied kinds of climate models to perform case simulation and mechanism experiment, but a reasonable explanation about the mechanisms of abrupt climate change in Holocene is still lacking. Here we used an Earth-system Model of Intermediate Complexity (EMIC), MPM-2, to simulate the global climate response to the Freshwater Flux Anomaly (FFA) at 8.2kaB.P. and 4.2kaB.P., including the Thermohaline Circulation (THC), its possible effects on global climate, the differences between two hemispheres, as well as the timescale for climate system to respond and to recover. The results intimate that oceans are sensitive to the strength of FFA, and the balance between the transportation ability of thermohaline circulation and the strength of FFA determines whether ocean circulation changes nonreversely. When FFA reaches some threshold, the equilibrium of ocean and climate will change. The forcing roles of two FFAs to ocean and atmosphere system are different. The first FFA is more important to climate state than that of the second one. Results also intimate that anomalies of North Atlantic Ocean will spread to other parts and regions over the world through interaction between different parts of the earth system, and appear different characters in the northern and southern Hemispheres. Study of this paper is heuristic to explore features of climate change, relations between different abrupt events in Holocene, and their potential effects on present climate.