Simulation and understanding of the major transitions in Quaternary climate dynamics

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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.