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中文摘要：
全新世暖湿气候背景下的代表性气候突变是发生在约8.2kaB.P.和4.2kaB.P.的气候突然变冷变干的事件。对于气候突变事件的出现,海洋环流被普遍认为是其中的关键环节。科学家们利用不同类型的气候模式进行过个例和机理模拟试验,但还未能对气候突变机理做出合理的解释。本研究使用一个中等复杂程度的地球系统模式EMIC（Earth-system Models Intermediate Complexity）MPM-2,模拟研究了全新世气候背景下北大西洋区域,淡水强迫机制作用对温盐环流以及全球气候的可能影响、气候系统响应和恢复时间特征以及南北半球的差异。模拟结果表明海洋对北大西洋淡水通量异常的强度响应敏感,海洋环流对热量和盐份的输送与淡水通量异常强度之间的平衡决定了温盐环流能否对淡水强迫产生不可逆转变,当淡水通量异常达到某一阈值后可能引起海洋和气候平衡态的改变。同时还发现,在气候变化过程中,两次淡水通量异常对海洋和大气系统的强迫作用是不同的,首次淡水通量异常对气候平衡态的影响要远大于其后的淡水通量异常。模拟结果还表明,北大西洋海洋的异常状况可以通过海洋、大气等各圈层相互作用传递到不同圈层和空间区域,在南北半球出现不同的响应特征。上述模拟结果对于认识全新世气候变化特征、不同突变事件之间的关系及其对现代气候的可能影响具有启发意义。
英文摘要：
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.
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