GRGC: Examining Isotopic Signals in the Geologic Record Through a General Circulation Model Approach

小行星9316691 一个令人印象深刻的氧和氢同位素记录网络，来自冰芯、湖芯、深海芯和树木年轮，现在可以在不同的时间段进行汇编。 这些记录有可能为过去气候过程的变化提供定量的见解，但如果不了解降水中同位素的基本驱动力，就无法完全认识到它们真正的气候意义。 简单的气团模型不能解释控制区域同位素分布的过程范围，因此将同位素示踪剂与大气环流模型（GCM）相结合是更全面地了解地质记录中记录的同位素信号的必要的第一步。 我们建议调查这些同位素记录的戈达德空间研究所的大气环流模式（GISS GCM）的手段。 我们将追求的主要问题是如何源水特性，空气质量的轨迹，空气质量混合的变化-所有的因素，必须有不同的气候周期与气候系统的主要组成部分-影响区域同位素分布。 在接下来的两年里，我们将进行一些古气候模拟，以确定模型水分源贡献和同位素场对边界条件（冰盖，海冰，海面温度等）特定变化的敏感性。 古气候模拟的结果将与我们将汇编的观测结果进行比较。 这种数据模式的比较将有助于确定北方半球气候系统中对形成同位素记录最重要的组成部分。 这种比较也将为GCM水文循环的可靠性和敏感性提供一个测试。

9316691 Charles An impressive network of oxygen and hydrogen isotopic records from ice cores, lake cores, deep sea cores and tree rings can now be compiled for a variety of time periods. These records potentially offer quantitative insight to past changes in climate processes, but their true climatic significance cannot be fully realized without knowledge of the fundamental driving forces for isotopes in precipitation. Simple air parcel models cannot account for the range of processes which control regional isotope distributions, and therefore the coupling of isotope tracers to a general circulation model (GCM) represents a necessary first step towards a more complete understanding of the isotope signals recorded in the geologic record. We propose to investigate these isotopic records by means of the Goddard Institute for Space Studies General Circulation Model (GISS GCM). The major issue we will pursue is how the changes in sourcewater characteristics, air mass trajectories, and air mass mixing-- all factors which must have varied over climate cycles with the major components of the climate system--affect regional isotopic distributions. Over the next two years, we will conduct a number of paleoclimatic simulations to determine the sensitivity of the model moisture source contributions and isotope fields to specific changes in boundary conditions (ice sheets, sea ice, sea surface temperature, etc.) Results of the paleoclimatic simulations will be compared to the observations, which we will compile. This data-model comparison will help identify the components of Northern Hemisphere climate system that are most important in shaping the isotope records. The comparison will also provide a test for the reliability and sensitivity of the GCM's hydrological cycle.