Simulation and understanding of the major transitions in Quaternary climate dynamics

了解过去300万年的气候变化仍然是一项科学挑战。古气候记录提供了关于第四纪气候旋回的丰富信息，并揭示了气候变异性制度的几个显着变化。这些转变的机制仍然没有得到正确的理解。虽然已经提出了一些假设，但由于缺乏适当的建模工具，这些假设的检验受到阻碍。我们建议用一个新的中等复杂性的地球系统模型来研究这些体制变化的性质，该模型将在现有的和全面测试的模型攀登者-2的基础上开发。尽管新的模型将具有比攀登者2号更高的空间分辨率，但它在计算上仍然是有效的，使我们能够在百万年时间尺度上进行实验。利用扰动物理方法获得的一系列模型实现，我们将进行一系列瞬变实验，以检验关于上新世-更新世转变(约2.7 Ma)、中上新世革命(约1.2-0.8 Ma)和中布鲁内斯事件(约430 ka)的机制的现有假说。最终目标是使用轨道强迫作为唯一规定的强迫来再现这些过渡，同时该模式将模拟大气组成、陆地沉积层的演变和风沙输送和沉积。有了这一点，我们有望在理解地球系统主要组成部分的非线性动力学方面取得实质性进展，如冰盖、海洋环流和碳循环，以及各种气候反馈的作用。我们还将评估利用关于过去300万年气候变异性的现有古气候信息的可能性，以更好地约束地球系统对外部作用力和内部扰动的敏感性和稳定性。

Understanding climate variability during the past 3 million years remains a scientific challenge. Paleoclimate records provide rich information about Quaternary climate cycles and reveal several pronounced changes in the regimes of climate variability. The mechanisms of these transitions are still not properly understood. Although a number of hypotheses have been proposed, testing of these hypotheses is hampered by the lack of an appropriate modeling tool. We propose to study the nature of these regime changes with a new Earth system model of intermediate complexity, which will be developed based on the existent and comprehensively tested model CLIMBER-2. Although the new model will have higher spatial resolution than CLIMBER-2, it will be still be computationally efficient to enable us to perform experiments at million-year time scales. Using an ensemble of model realizations obtained by a perturbed physics approach, we will perform a set of transient experiments to test existing hypotheses concerning the mechanisms of the Pliocene-Pleistocene Transition (ca. 2.7 Ma), Mid-Pliocene Revolution (between 1.2 and 0.8 Ma) and Mid-Brunhes Event (ca. 430 ka). The final goal is to reproduce these transitions using orbital forcing as the only prescribed forcing while atmospheric composition, evolution of terrestrial sediment layer and aeloian dust transport and deposition will be simulated by the model. With this we expect to make a substantial progress in understanding the non-linear dynamics of the principal components of the Earth system, such as ice sheets, ocean circulation and carbon cycle, as well as the role of various climate feedbacks. We will also assess a possibility of using the available plaeoclimate information about climate variability over the past 3 million years to provide better constraints on Earth system sensitivity and stability to external forcings and internal perturbations.