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

在全球温暖、均匀的白垩纪时期沉积的地层保存了一个独特的自然实验记录，这将有助于我们更好地理解综合地球系统的动力学行为。西部内白垩纪海道（WIKS）的地层记录为研究提供了无与伦比的机会，因为大量数据集的可用性已经成熟，可以进行综合和分析。利用WIKS作为工作“实验室”，我们建议：(1)了解全球气候系统及其在极端温暖时期的变率；(2)验证与当前条件有很大不同的气候模式；(3)确定WIKS跨越C/T边界对全球和区域强迫因子的海洋、生物和化学响应；(4)更好地界定这些海道响应与西部内陆盆地地质记录之间的联系。在本研究中，我们将在不同的WIKS数据集的约束下，对代表主要的二级海平面循环（Greenhorn cycle）的不同阶段的三个时间切片进行一系列分层大气和海洋模式模拟。对于每个时间片，我们将：(1)从文献中确定全球古地理、古地形、海平面和大气pCO2；(2)利用NCAR群落气候模式（CCM）进行全球气候基线数值试验；(3)开展了一系列CCM对海平面变化、高低地形、变轨道参数和变pCO2的敏感性实验；(4)利用CCM运行的日风应力和蒸发减去降水驱动三维湍流沿海海洋模式，研究WIKS对CCM变化的敏感性；(5)通过跟踪循环模型中的化学示踪剂并建立营养物、氧和盐度的盒子模型，研究这些循环变化可能对有机碳产量和碳氧同位素的影响；(6)通过组合岩相图、底栖生物相/氧梯度图以及推断的温度、古盐度和有机碳分布图来验证这些预测。

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.