Extreme climates in the Proterozoic and early Palaeozoic: model experiments

对新元古代和古生代的地质研究表明，地球经历了全球性的变冷事件，伴随着遍布整个大陆的极端冰川的形成，以及赤道附近的海冰形成。现有的数据提供了证据，至少有三个主要的冰川在晚元古代和一个在奥陶纪末期的古生代（800-550和490-443 Ma）。本提案的目的是研究由于气候变量的变化而出现的极端气候。利用耦合大气/海洋环流模式（AOGCM），并包括碳循环系统中，我想调查的地理陆地分布，大气CO2浓度，日照和海气气体交换的变化如何影响气候和极端气候在地球上创造的情况。通过进行一些模型实验，可以研究气候系统的敏感性和对触发气候系统质的变化的阈值的评估。零维和一维模型提出，相对于太阳辐射的连续变化，存在着大气的多个稳定状态。使用大气环流模型，我预计气候系统的双稳态行为相对于气候变量的变化，如CO2浓度，或由于扰动的碳循环，或改变的陆地覆盖所造成的大陆冰盖的增长。对由于完全不同的陆地结构而改变的海洋环流以及随之而来的海洋热输送的研究也是这项研究的一个重要部分。

Geological studies of the Neoproterozoic Era and Palaeozoic Era have suggested that the Earth has experienced global cooling events accompanied by formation of extreme glaciers, which spread over the entire continents, and by sea-ice formation near the equator. The available data give evidence for at least three major glaciations in the Late Proterozoic Era and for one at the end of Ordovician period of the Palaeozoic Era (800-550 and 490-443 Ma.). The objective of the present proposal is to study the occurrence of extreme climates due to the changes of the climatic variables. Using a coupled atmospheric/oceanic general circulation model (AOGCM) and including a carbon cycle in the system, I would like to investigate how changes of the geographical land distribution, atmospheric CO2 concentration, insolation and the air-sea gas exchange could influence the climate and create circumstances for extreme climates on the Earth. Performing a number of model experiments, the sensitivity of the climate system and evaluation of thresholds, which trigger the qualitative changes in the climate system, could be investigated. Zero and one-dimensional models propose that multiple steady states of the atmosphere exist with respect to a continuous change of the solar insolation. Using a general circulation model I expect bi-stable behavior of the climate system relative to changes of climatic variables like CO2 concentration, or due to perturbations in the carbon cycle, or alteration of the land albedo caused by the growth of the continental ice sheets. Investigation of the oceanic circulation, changed by the completely different land configuration, and of the consequent oceanic heat transport, is also an important part of this research.