Developing Köppen climate zone maps for key paleoclimate events: quantitative compilations and interpolation improve Late Cretaceous predictions

Abstract:

Köppen(-Geiger) climate classifications are a widely-used scheme for identifying key climate parameters and displaying these spatially to highlight links between climate and ecosystem. Such a system is central to understanding and predicting future conditions resulting from global change, and qualitative versions have historically been applied to deep time in an effort to clarify paleoclimate shifts and impacts. Recent work has developed parameters/thresholds for quantitative reconstruction of a true Köppen classification scheme for paleo-applications, and new progress in both spatial interpolation of climate proxy data and large-scale compilations of paleoclimate proxies has allowed the development of improved predictions for key paleoclimate events and states such as the Late Cretaceous greenhouse. Here we use new quantitative paleoclimate proxy compilations from four Late Cretaceous time slices (Cenomanian, Coniacian/Santonian, Campanian, and Maastrichtian) on multiple continents (North America, Europe, Australia), and apply inverse distance weighting (IDW) methods to create spatial interpolations of relevant paleoclimate parameters, and develop detailed Köppen climate zone maps for these periods/regions. The initial results from this new analysis reveal the expansion and subsequent contraction of the Tropical Savanna and Maritime Temperate climate zones across Late Cretaceous North America and the onset of polar cooling during the Maastrichtian. Beyond serving as useful references for paleoclimate models and further paleoecological work on these periods/regions, these maps have implications for existing questions in biogeography such as climatic controls on “provincialism” in Late Cretaceous vertebrates (e.g., dinosaurs) and other groups, or environmental niches and climatic tolerances of key ancestors (e.g., early mammals). Furthermore, this methodology has applications for other time periods and regions, providing a framework for developing and comparing predictive models of climate/environments/ecosystems in these and additional regions during other key events or climate states which may have relevance for the future.