Controls on Variations in the Isotope Composition of Precipitation during Warm Climates

该奖项支持使用具有同位素能力的环流模型来量化地理、全球气候和轨道对降水氧同位素组成的影响的研究。研究人员将使用GENESIS一般循环模型（GCM）进行一系列敏感性测试，其中包括水文循环中的水同位素示踪剂。研究人员和她的同事们将比较在适合现代和早期古近纪时期的边界条件下进行的实验，目的是在各种边界条件和时间尺度上检查降雨、大陆径流和高纬度降雪的同位素组成的可变性。具体而言，研究人员将根据气候物理和水同位素分馏的第一性原理提供淡水氧同位素的估计。该研究将提供在许多前新近纪气候的典型温暖温度下所见的非线性降水氧同位素-温度关系的定义。对适合于比现代更温暖气候的边界条件的降水氧同位素的合理范围进行量化，将使我们对来自海洋和大陆代用记录的古温度、水汽输送和季节性的估计有更大的信心，这些记录目前依赖于同位素-温度关系、氧同位素淡水值和淡水通量估计的假设。这项研究的结果可能会对更广泛的科学界产生广泛的影响，因为它提高了模型中水同位素数值模拟的可靠性，可以很容易地应用于现代气候问题和任何地质时期。

This award supports research using an isotope-capable general circulation model to quantify geographic, global climatic, and orbital effects on the oxygen isotopic composition of precipitation. The researcher will run a series of sensitivity tests will be performed using the GENESIS general circulation model (GCM) with water isotope tracers included in the hydrologic cycle. The researcher and her colleagues will make comparisons among experiments performed with boundary conditions appropriate for the modern and early Paleogene time period with the aim of examining variability in the isotopic composition of rainfall, continental runoff, and high latitude snowfall over a wide variety of boundary conditions and time scales.Specifically, the researcher will provide estimates of freshwater oxygen isotope based on first principles of climate physics and water isotope fractionation. The research will provide a definition of the nonlinear precipitation oxygen isotope-temperature relationships seen at the warm temperatures typical of many pre-Neogene climates. Quantification of plausible ranges in precipitation oxygen isotopes for boundary conditions appropriate for warmer-than-modern climates will allow greater confidence in estimates of paleotemperature, water vapor transport, and seasonality from marine and continental proxy records that currently rely on assumptions of isotope-temperature relationships, oxygen isotope freshwater values, and freshwater flux estimates. The results of this research are likely to have a broad impact on the wider science community through improvements in the reliability of numerical simulations of water isotopes within a model that can be easily applied to modern climate problems and any geologic time period.