Climate Forcing, Ocean Circulation, and the Geologic Record of Global Change Across the Cenomanian/Turonian Boundary, Western Interior Seaway of North America

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Strata deposited during the globally warm, equable, Cretaceous period preserve the record of a unique natural experiment which will help us better understand the dynamical behavior of the integrated earth system. The stratigraphic record of the Western Interior Cretaceous Seaway (WIKS) provides an unparalleled opportunity for study because of the availability of substantial data sets that are ripe for synthesis and analysis. Using the WIKS as a working "laboratory" we propose to: (1) understand the global climate system and its variability during a period of extreme warmth; (2) validate climate models for conditions substantially different from the present day; (3) determine the oceanographic, biological, and chemical responses of the WIKS across the C/T boundary to both global and regional forcing factors; and (4) better define the links between these seaway responses and the geologic record of the Western Interior Basin. In this study a series of hierarchical atmospheric and ocean model simulations constrained by the diverse WIKS dataset will be performed for three times slices representing different stages of a major second order sea level cycle (Greenhorn cyclothem). For each time slice we will: (1) determine the global paleogeography, paleotopography, sea level, and atmospheric pCO2 from the literature; (2) perform baseline numerical experiments of global climate using the NCAR Community Climate Model (CCM); (3) perform a series of CCM sensitivity experiments to sealevel changes, low versus high topography, variable orbital parameters, and variable pCO2; (4) investigate the sensitivity of the WIKS to CCM variation by using daily wind stresses and evaporation minus precipitation from the CCM runs to drive a three-dimensional, turbulent flow, coastal ocean model; (5) investigate the influence these circulation changes might have on organic carbon production, and carbon and oxygen isotopes by following chemical tracers in the circulation model and developing box models of nutrients, oxygen, and salinity; and (6) test these predictions by assembling lithofacies maps, benthic biofacies/oxygen gradient maps, and maps of inferred temperature, paleosalinity and organic carbon distribution.