Doctoral Dissertation Research in Geography and Regional Science

地理学与区域科学博士论文研究

• 批准号: 9206725
• 负责人: Patricia McDowell
• 金额: $ 1万
• 依托单位: University of Oregon Eugene
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-07-01 至 1994-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9206725&HistoricalAwards=false
• 关键词: Doctoral; Dissertation; Research; Geography; Regional

Paleolakes in closed basins are sensitive indicators of past climatic variations. The chronology of the fluctuations in the level of a particular lake can provide evidence of changes in local climate, while basin-wide variations reveals past changes in the large-scale circulation of the atmosphere. One hypothesis resulting from lake studies states that latitudinal shifts in the jet stream and associated surface weather systems, resulting from decay of the continental ice sheet, affected the timing of high stands of closed basin lakes during the late Pleistocene. This project will develop lake-level chronologies during a critical interval of the late Quaternary period for three basins in eastern Oregon. These chronologies will be used to test hypotheses concerning atmospheric circulation controls of regional climatic change. Chronologies will be determined from radiocarbon dates on samples collected from shoreline sediments. A physically based evaporation model and a water balance model will be used to estimate the range of climatic conditions consistent with a specific lake level. The resulting climate scenarios will be employed in a test of the hypothesis that high lake stands were governed by the mean seasonal positions of the jet stream over the western United States. This research will contribute to the regional geomorphology of a region in need of additional study, and it will further our understanding of the mechanisms that control regional climate changes, and thus the responses of hydrological systems.

封闭盆地古湖泊是反映过去气候变化的敏感指标。特定湖泊水位波动的年表可以提供当地气候变化的证据，而盆地范围的变化则揭示了过去大尺度大气环流的变化。从湖泊研究中得出的一个假设认为，由于大陆冰盖的衰变，急流和相关地表天气系统的纬度变化影响了晚更新世封闭盆地湖泊的高峰时间。该项目将在俄勒冈州东部的三个盆地的晚第四纪的一个关键时期开发湖平面年代学。这些年表将用于检验关于大气环流控制区域气候变化的假设。将根据从海岸线沉积物中收集的样品的放射性碳年代来确定年代。将使用基于物理的蒸发模式和水平衡模式来估计与特定湖泊水位相一致的气候条件范围。由此产生的气候情景将用于检验这样一种假设，即高湖林是由美国西部上空急流的平均季节位置决定的。这项研究将有助于进一步研究一个地区的区域地貌，并将进一步了解控制区域气候变化的机制，从而进一步了解水文系统的响应。