Reconstructing climate variability and aridity in the Sierra Nevada, CA, based on isotopic evidence in sediments from Swamp Lake, Yosemite

该奖项是根据2009年《美国复苏和再投资法案》(公法111-5)资助的。了解加州气候如何对多个时间尺度上的全球和区域强迫机制做出反应，对于管理稀缺的水资源和预测自然模式将如何与未来气候变暖相互作用至关重要。鉴于仪器记录较短，只有古气候记录才能为理解较长时间尺度上的气候变异性和生态系统反应提供基础，捕捉控制区域气候和决定供水的十年和百年尺度过程的许多周期，以及在不同气候制度下经历的极端条件的范围。这项赠款基于从内华达山脉中部沼泽湖发现的19,000年沉积序列中的同位素证据，开发了加利福尼亚州气候变异性的新记录。这一较长的记录允许高分辨率(20-50年)重建以前确定的全新世中期和晚期干旱时段，以便更好地了解长期干旱背后的年代际气候变化。前人的工作表明，从沉积有机质(OM)中提取的生物标志物化合物中的氢同位素(del-D)测量提供了一个强大的古水文工具。目前的项目使用陆地植物和水生生物标志物的Del-D标记来重建塞拉利昂过去的降水模式、蒸发平衡和水的可获得性。利用一套有机质替代指标(总碳氮、碳氮比、del-13C、del-15N、生物标志物丰度)的平行记录追踪了有机质来源、湖泊生产力和其他生态系统对气候条件变化的反应。气候重建得到了一项多年实地研究的支持，该研究旨在了解湖盆的同位素水文学，用仪器记录进行校准，并与沼泽湖、内华达山脉和整个加利福尼亚州的现有记录进行比较。内华达山脉晚更新世-全新世气候变异性十年至百年分辨率记录的发展代表着加州古气候研究向前迈出的重要一步。这样的记录具有直接的社会重要性，因为这些时间尺度上的过程决定了水的供应，影响了动植物的分布，并调节了洪水和干旱等更频繁事件的发生。该项目为未被充分代表的本科生和少数族裔本科生提供参与研究的机会，并参与旨在加强他们领导能力的项目。为AGEP项目的学生协调辅导，并在加州大学圣迭戈分校开设“第一个研究生地质学项目--Geokids”，并开设K-12教育课程“交流海洋科学”。该项目参与了美国国家科学基金会资助的国家教育项目“科学日记”和“儿童科学挑战”(通过星球的脉搏，NPR)。国际和平研究所还在开发一门以古海洋学和古气候学为主题的探究式课程。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).An understanding of how climate in California responds to global and regional forcing mechanisms on multiple timescales is crucial for the management of scarce water resources and for predicting how natural patterns will interact with future climate warming. In light of the short instrumental record, only paleoclimatic records can provide the basis for understanding climate variability and ecosystem responses on longer timescales, capturing many cycles of the decadal and centennial-scale processes that control regional climate and determine water supplies, as well as the range of extreme conditions experienced under different climatic regimes.This grant develops new records of climatic variability in California based on isotopic evidence in the 19,000-year sedimentary sequence recovered from Swamp Lake in the central Sierra Nevada. This longer record allows high-resolution (20-50 yr) reconstructions for previously identified dry intervals in the mid- and late-Holocene, in order to better understand the decadal climate variability underlying long-term droughts. Previous work demonstrated that measurements of hydrogen isotopes (del-D) in biomarker compounds extracted from sedimentary organic matter (OM) provides a powerful paleohydrologic tool. The current project uses coupled del-D signatures of terrestrial plant and aquatic biomarkers to reconstruct past precipitation patterns, evaporative balance and water availability in the Sierra. A parallel record utilizing a suite of OM proxies (total C & N, C/N ratio, del-13C, del-15N, biomarker abundances) traces OM sources, lake productivity and other ecosystem responses to changing climate conditions. Climate reconstructions are supported by a multi-year field study to understand the isotope hydrology of the lake basin, calibration with the instrumental record, and comparisons with existing records from Swamp Lake, the Sierra Nevada, and California as a whole. The development of a decadally- to centennially-resolved record of Late Pleistocene-Holocene climatic variability for the Sierra Nevada represents a major step forward for paleoclimatic research in California. Such records are of direct societal importance because processes on these timescales determine water supplies, influence the distribution of plants and animals, and modulate the occurrence of higher-frequency events such as floods and droughts.The project provides involvement for underrepresented and minority undergraduate students in research, and participation in programs that aim to strengthen their leadership skills. Mentoring is coordinated for students from the AGEP program, and a 'first grad geology program - Geokids' at UCSC, and a K-12 education class 'Communicating ocean sciences' is offered. The project participates in the NSF-funded national education programs 'Science Diaries' and 'Kids Science Challenge' (through Pulse of the Planet, NPR). The PI also is developing an inquiry-based curriculum on the topic of paleoceangraphy and paleoclimatology.