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，以及赤道附近海冰的形成。现有资料表明，晚元古代至少有3次大冰期，古生代奥陶纪末有1次大冰期（800 ~ 550 Ma和490 ~ 443 Ma）。本提案的目的是研究由于气候变量的变化而导致的极端气候的发生。我想利用一个耦合的大气/海洋环流模式（AOGCM），并在系统中加入碳循环，研究地理陆地分布、大气CO2浓度、日照和海气交换的变化如何影响气候，并为地球上的极端气候创造条件。通过进行一些模式实验，可以对触发气候系统质变的气候系统敏感性和阈值评估进行研究。零和一维模式表明，相对于太阳日照的连续变化，大气存在多种稳定状态。使用一般环流模型，我预计气候系统的双稳定行为与气候变量的变化有关，如二氧化碳浓度，或由于碳循环的扰动，或由于大陆冰盖的增长引起的陆地反照率的改变。研究完全不同的陆地形态所改变的海洋环流，以及由此产生的海洋热输运，也是本研究的重要组成部分。

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.