Doctoral Dissertation Research: High-Resolution Time Series of Eastern Sierra California Climate Over the Late Quaternary

博士论文研究：晚第四纪加利福尼亚山脉东部气候的高分辨率时间序列

• 批准号: 0101268
• 负责人: Glen MacDonald
• 金额: $ 0.94万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-04-01 至 2003-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0101268&HistoricalAwards=false
• 关键词: Doctoral; Dissertation; Research; Resolution; Time

Understanding the severity of past drought events and assessing the linkages of these events to conditions in the eastern Pacific is essential for long-term water resource planning in California and adjacent portions of the southwestern United States. This doctoral dissertation research project will use the remains of aquatic organisms, specifically midge fly larvae, preserved within the sediments of small, climatically sensitive Sierran lakes to reconstruct a high-resolution record of paleotemperature and paleohydrology for California during the late-Quaternary (past 13,000 years). This research is an expansion of an earlier NSF-supported project that assessed how present-day differences in air temperature and precipitation, lake water temperature, salinity, depth, and surrounding vegetation are reflected in the modern elemental chemistry and oxygen isotopic composition of lake waters, and the chironomids (midge flies), cladocera (crustaceans), diatoms (unicellular algae), pollen, and stomates found in Sierran lake sediments. Previous work had determined that the modern distribution of midges in Sierran lakes is controlled by summer surface lake-water temperature, lake depth, elevation, and iron. The relationship between midge fly distributions and surface lake-water temperature also have been characterized through the development of a transfer function (mathematical formulae that express the value of a specific environmental variable as a function of plant or animal species composition data). This dissertation research project will apply the new transfer function to the fossil midge assemblages contained within late-Quaternary lake sediment cores, thereby enabling a high-resolution reconstruction of paleotemperature for California during the late-Quaternary.Earlier paleoenvironmental research in the Sierra Nevada indicates that drought events of greater severity than those experienced during the instrumental period (past 100 years) have occurred in eastern California during the late-Holocene (last 3,000 years). Because of the fragmentary nature of the existing paleoenvironmental records, however, understandings of earlier drought periods is limited. This research project will provide a high-resolution record of the inherent variability of eastern California climate during the past 13,000 years. More specifically, this project will use the remains of midge fly larvae preserved in Sierran lake sediments to provide a sensitive and detailed history of the climatic changes that occurred in the eastern Sierra Nevada, California over the last 13,000 years. The results of this work will assist hydrologists, paleoclimatologists, oceanographers, and climate modelers in understanding the timing, magnitude, and causal mechanisms associated with high frequency climate oscillations evident in California during the late-Quaternary. The expected results should assist water resource managers as they attempt to adequately plan for future water resource needs. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.

了解过去干旱事件的严重程度并评估这些事件与东太平洋条件的联系，对于加州和美国西南部邻近地区的长期水资源规划至关重要。 这个博士论文研究项目将使用的水生生物，特别是蠓幼虫，保存在小，气候敏感的Sierran湖泊的沉积物中，重建高分辨率的记录古温度和古水文加州在第四纪晚期（过去13,000年）。 这项研究是早期NSF支持的项目的扩展，该项目评估了当今空气温度和降水，湖水温度，盐度，深度和周围植被的差异如何反映在现代元素化学和湖泊沃茨的氧同位素组成以及摇蚊中（吸浆虫），枝角类（甲壳类），硅藻（单细胞藻类），花粉，和气孔在谢尔兰湖沉积物中发现。 以前的工作已经确定，现代分布的蠓在谢尔兰湖控制夏季表层湖水温度，湖深，海拔和铁。 还通过建立一个传递函数（用数学公式表示某一特定环境变量值随植物或动物物种组成数据的变化）来确定摇蚊分布与表层湖水温度之间的关系。 本论文研究项目将新的传递函数应用于晚第四纪湖泊沉积物岩芯中的化石蠓组合，早期内华达州山脉的古环境研究表明，比仪器测量期间经历的更为严重的干旱事件，（过去100年）发生在东部加州在晚全新世（过去3,000年）。 然而，由于现有的古环境记录的零碎性，对早期干旱期的了解是有限的。 这项研究项目将提供一个高分辨率的记录，在过去的13,000年中，东部加州气候的固有变化。 更具体地说，该项目将利用保存在谢尔兰湖沉积物中的蚊幼虫遗骸，提供加州东部内华达州在过去13,000年中发生的气候变化的敏感和详细的历史。 这项工作的结果将有助于水文学家，古气候学家，海洋学家和气候建模者了解的时间，幅度和因果机制与高频率的气候振荡明显的加州在第四纪晚期。 预期成果应有助于水资源管理人员努力为今后的水资源需求作出适当规划。 作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立的研究生涯。