Constraining Late Paleozoic Climate, CO2 Levels, and Ice Sheet Volumes: Integration of Oxygen Isotopes with Climate and Ice Sheet Models

最近的发展提供了一个机会，耦合的第一次两种方法来估计古生代大陆冰量：氧同位素（18 O/16 O）古测温和冰盖气候模型（ISCM）。 该提案要求资金使用海洋化石和ISCM的氧同位素数据来估计地球过去关键时期的温度变化，冰量和二氧化碳水平。 这项研究将跨越泥盆纪晚期到二叠纪中期，这是地球上最后一个温室-冰库-温室循环。 作为第一步，该模型将在更新世晚期（完全冰川化）和始新世早期或白垩纪中期（无冰）的端元气候上进行测试。 这将检查模型的能力，重现温度分布，并允许比较现有的同位素数据。 该模型将应用于古生代在两种模式。 首先，将从Berner（1997年，Science 76：544-546）的地球化学模型输入CO2水平，从而可以估计全球温度变化和冰量。 使用模拟温度和氧同位素（d18 O）数据从腕足动物壳，海水d18 O可以计算和冰体积重新确定。 不同的CO2水平将被反复输入，以努力收敛到一个解决方案，其中温度分布，CO2水平，和冰体积是相互一致的同位素数据。 这项研究所需的大部分数据都可以从以前的研究中获得，特别是从第一个PI和他的同事那里。 将收集选定时间段的其他数据（例如，早石炭世和早二叠世），使用俄罗斯和澳大利亚合作者提供的在俄罗斯收集的样品。 这将允许开发一个可靠的d18 O记录晚古生代。这项研究是开发确定冰量和二氧化碳水平的新方法的第一个探索性步骤，其中冰盖和气候的物理动力学与通过氧同位素分析获得的精确数据相结合。 最终目标是估计地球过去5.4亿年的大气二氧化碳水平。 由于要检查的参数空间区域禁止使用更昂贵的模型，因此将使用计算机高效的ISCM进行首次研究。 随后的研究将采用更复杂和昂贵的模型，重点放在关键问题和模型/数据不一致的领域。

Recent developments provide an opportunity to couple for the first time two methods for estimating Paleozoic continental ice volume: oxygen isotope (18O/16O) paleothermometry and ice sheet-climate models (ISCMs). This proposal requests funds to use oxygen isotopic data for marine fossils and ISCMs to estimate temperature variations, ice volumes, and CO2 levels during a key interval in Earth's past. The study will span late Devonian to mid-Permian time, Earth's last greenhouse-icehouse-greenhouse cycle. As a first step, the model will be tested on more recent end-member climates, those of the late Pleistocene (fully glaciated) and the Early Eocene or Mid-Cretaceous (ice free). This will examine the model's ability to reproduce temperature distributions and permit comparison to existing isotopic data. The model will then be applied to the Paleozoic in two modes. First, CO2 levels will be inputted from the geochemical model of Berner (1997, Science 76:544-546), permitting estimates of global temperature variation and ice volume. Using modeled temperatures and oxygen isotopic (d18O) data from brachiopod shells, seawater d18O can be calculated and ice volume redetermined. Different CO2 levels will be entered iteratively in an effort to converge on a solution in which the temperature distribution, CO2 level, and ice volume are mutually consistent with the isotopic data. Much of the data necessary for the study are available from previous studies, especially from those of the first PI and his coworkers. Additional data will be collected for select intervals (e.g., Lower Carboniferous and Early Permian) using samples in hand, provided by Russian and Australian collaborators, and collected in Russia. This will permit development of a reliable d18O record for the Late Paleozoic. This study is the first exploratory step in the development of a new methodology for determining ice volume and CO2 levels, in which the physical dynamics of ice sheets and climate are combined with the precise data available through oxygen isotope analysis. The ultimate goal is to estimate atmospheric CO2 levels for Earth's last 540 million years. This premiere study will be performed using a computer-efficient ISCM, as the areas of parameter space to be examined prohibit the use of more expensive models. Subsequent studies will employ more sophisticated and expensive models to focus on key problems and areas of model/data disagreement.