Ragon C, Vérard C, Kasparian J, Brunetti M
Group of Applied Physics and Institute for Environmental Sciences, University of Geneva, 66 Bd Carl-Vogt, Geneva 4, 1211, Switzerland.
Section of Earth and Environmental Sciences, University of Geneva, 13 Rue des Maraîchers, Geneva, 1205, Switzerland.
Sci Rep. 2024 Oct 30;14(1):26136. doi: 10.1038/s41598-024-76432-8.
Due to spatial scarcity and uncertainties in sediment data, initial and boundary conditions in deep-time climate simulations are not well constrained. On the other hand, depending on these conditions, feedback mechanisms in the climate system compete and balance differently. This opens up the possibility to obtain multiple steady states in numerical experiments. Here, we use the MIT general circulation model to explore the existence of such alternative steady states around the Permian-Triassic Boundary (PTB). We construct the corresponding bifurcation diagram, taking into account processes on a timescale of thousands of years, in order to identify the stability range of the steady states and tipping points as the atmospheric CO content is varied. We find three alternative steady states with a difference in global mean surface air temperature of about 10 °C. We also examine how these climatic steady states are modified when feedbacks operating on comparable or longer time scales are included, namely vegetation dynamics and air-sea carbon exchanges. Our findings on multistability provide a useful framework for explaining the climatic variations observed in the Early Triassic geological record, as well as some discrepancies between numerical simulations in the literature and geological data at PTB and its aftermath.
由于沉积物数据存在空间稀缺性和不确定性，深时气候模拟中的初始条件和边界条件受到的限制不足。另一方面，取决于这些条件，气候系统中的反馈机制会以不同方式相互竞争和平衡。这使得在数值实验中获得多个稳定状态成为可能。在此，我们使用麻省理工学院的通用环流模型来探究二叠纪 - 三叠纪边界（PTB）附近此类替代稳定状态的存在情况。我们构建了相应的分岔图，考虑了数千年时间尺度上的过程，以便在大气二氧化碳含量变化时确定稳定状态的稳定范围和临界点。我们发现了三种替代稳定状态，其全球平均地表气温相差约10摄氏度。我们还研究了在纳入作用于可比或更长时间尺度的反馈时，即植被动态和海气碳交换时，这些气候稳定状态是如何被改变的。我们关于多稳定性的研究结果为解释早三叠世地质记录中观测到的气候变化以及文献中的数值模拟与PTB及其后续地质数据之间的一些差异提供了一个有用的框架。
