Extreme climates in the Proterozoic and early Palaeozoic: model experiments

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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.