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Site Map / Index This page last modified: 7th January, 2008 ŠPaul Markwick 2000-2008 |
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Markwick, Paul J. & Valdes, Paul J. (2002) A quantitative evaluation and application of the results of a Maastrichtian (Late Cretaceous) coupled ocean-atmosphere experiment using the HadCM3 AOGCM Cretaceous climate and oceanography Workshop Abstract The Maastrichtian (Late Cretaceous) is a stage better known for its abrupt, enigmatic end, rather than for any inherent interest. Yet the K-T extinction event and its consequences, can only be understood in the context of the contemporary climate and environment. The Maastrichtian is a time of global cooling, but with no persuasive evidence of large-scale polar glaciation. Seaways, though beginning to close, continued to dominate the geography of North America, Eurasia, South America and North Africa. The Arctic was almost fully land-locked, whilst in Asia highlands extended from Indonesia north through China and into NE Russia. It is a stage with a large terrestrial and marine geological record on all continents, and is present in a significant number of DSDP and ODP sites. Terrestrial fossil localities, with many recognizably modern forms, extend from the Antarctic Peninsular to Alaska, and throughout the continental interiors or North America and Asia. As such the Maastrichtian provides an ideal time interval for which to model the climate, and then evaluate the results based on observations. A series of atmosphere (AGCM) and coupled ocean-atmosphere (AOGCM) model experiments have been run using the latest Hadley Centre model, HadCM3. The details of this model, boundary conditions, and the climate and ocean results are described in a separate presentation in this workshop (Valdes). Here we will present the outcome of a quantitative and qualitative evaluation of the 'veracity' of the model experiments using a comprehensive dataset of geological climate proxies, including fossil vertebrates, megafloras, paleosols, and stable isotope geochemistry. This quantitative analysis is in progress at the time of writing this abstract but will be completed by the time of the meeting. Preliminary assessment indicates that the AOGCM experiment better replicates 'observations' than existing AGCM experiments. While such data-model comparisons increase our understanding of model behaviour, the integration of data with carefully designed model experiments can be also used to address other geological problems, for which we provide some examples. This is only possible because of the compilation of a comprehensive dataset of geological, tectonic and paleontological information, and the construction of a detailed, 'hydrologically-correct,' global paleo-topographic and bathymetric digital elevation model (DEM). This geography not only supplies an essential boundary condition for the modelling experiments, but also provides the context for investigating and further understanding processes on the surface of the Maastrichtian Earth, including the distribution and evolution of life. |
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