High-Resolution Climatic Variability in the Southwestern U.S. During the Last Millennium

ATM-9615875 Ku，南加州德隆大学标题：美国西南部的高分辨率气候变率。在过去的千年中，该奖项支持一个研究项目，该研究项目旨在开发一种有效的替代工具，使PI能够重建美国西南部过去千年在亚十年(3-10年)时间尺度上的降水量变率。这是一个与厄尔尼诺/南方涛动(ENSO)事件有关的大气遥相关区域(至少在南部)。其关键方法是对位于俄勒冈州、加利福尼亚州和内华达州N-S样带的闭盆型湖泊中提取的碳酸盐沉积物进行高分辨率氧同位素测量。这种方法的基础在于这样一个事实，即通过降雨和径流进入封闭盆地湖泊的水主要是通过蒸发离开的，而湖泊的同位素组成反映了用于监测区域气候变化的水文平衡，特别是在给定时间的降水变异性。湖相沉积物中的自生碳酸盐矿物记录了湖水同位素组成的过去变化。最近在莫诺湖进行的一项研究验证了拟议研究的可行性。该方法将允许PIs评估水汽来源(来自三个气候区域：太平洋、大陆和墨西哥湾)及其相对强度，并检测风暴路径在时间域中的任何变化。预计这项研究将使PIS能够评估诸如小冰期、中世纪暖期和ENSO等气候异常，并有助于理解亚十年气候变化的原因和动力学。

Abstract ATM-9615875 Ku, Teh-Lung University of Southern California Title: High-Resolution Climatic Variability in the Southwestern U.S. During the Last Millennium This award supports a research project aimed at developing an effective proxy tool which will enable the PIs to reconstruct the precipitation variability on sub-decadal (3-10 years) time scales for the past millennium in the southwestern U.S. This is a region (at least the southern part) of atmospheric teleconnection associated with the El Nino/Southern Oscillation (ENSO) events. The key approach is to employ the high-resolution oxygen isotopic measurement on dated carbonate sediments retrieved from closed- basin lakes located along a N-S transect in Oregon, California and Nevada. The basis for the approach lies in the fact that water entering a closed-basin lake via rain and runoff mostly leaves by evaporation, and the lake's isotopic composition reflects the hydrologic balance that serves to monitor the regional climate change, especially the precipitation variability, at a given time. Past variations of lake water isotopic composition are recorded by authigenic carbonate minerals of the lacustrine sediment. The feasibility of the proposed research has been tested in a recent study conducted in Mono Lake. The method will allow the PIs to assess the moisture sources (from three climatic regimes: Pacific, continental, and Gulf of Mexico) and their relative strengths and detect any shifts in storm track in the time domain. It is anticipated that the study will allow the PIs to evaluate such climatic anomalies as the Little Ice Age, Medieval Warm Period, and ENSO, and contribute to the understanding of the causes and dynamics of sub-decadal climatic variability.