Abstract: The responses of the global mean climate and the ENSO to a substantial weakening of the Atlantic Meridional Overturning Circulation (AMOC) are studied using water-hosing experiment in a coupled ocean-atmosphere general circulation model. With 1 Sv freshwater input in the North Atlantic, the AMOC slows down rapidly and weakens by almost 90%, reducing the northward oceanic heat transport, leading to a sea surface temperature (SST) dipole in the Atlantic. Through atmospheric teleconnections and local air-sea interaction, warm SST anomalies are found over the tropical Pacific. However, neither zonal SST gradient nor zonal wind stress changes significantly. The depth and slope of thermocline in tropical Pacific do not change too much, either. Accordingly, the variability of ENSO activity is essentially unchanged. These results indicate that in this model, fresh water perturbation may influence global mean climate, but has little impact on ENSO.

Key words: thermohaline, ENSO, water-hosing, AMOC

摘要： 利用一个完全耦合的海气模式, 通过对比分析两组试验中海表温度、盐度、风应力等气候态变化特征以及ENSO强度和频率的变化, 研究热带太平洋气候平均态及年际变率对热盐环流减弱的响应。在北大西洋高纬地区注入1 Sv淡水后, 大西洋经向翻转流(AMOC)减弱约90%, 这直接导致向北的经向热量输送减少, 使北大西洋有明显降温, 南大西洋略有升温。这些变化会经过大气和海洋的远程传播以及局地海气反馈作用, 影响热带太平洋气候平均态: 赤道东西太平洋的SST都略有增温, 但纬向温度梯度和纬向风应力并没有太大变化, 赤道太平洋温跃层的深度和倾斜度也基本保持不变。相应地, ENSO强度和频率也没有明显变化。由此得出结论: 热盐环流减弱会引起全球气候平均态的变化, 但对热带太平洋的年际变率没有太大影响。

关键词: 热盐环流, ENSO, 淡水试验, 大西洋经向翻转流(AMOC)