Collaborative Research/RUI: Assessing Multi-scale Holocene Climate Variability in Western North America Using Sediments from Lake Elsinore (Southern CA)

北美西部淡水的供应和质量与自然气候变化直接相关。在有关时间尺度上确定气候变化的能力受到观测和仪器记录持续时间短的限制。在南加州，对长时间、高分辨率的古气候记录的需求尤为迫切，那里有2000多万人容易受到气候变化的影响。这笔拨款将利用埃尔西诺湖的沉积物为南加州开发第一个完整的陆地全新世气候记录，并将该记录与该地区其他年代久远的陆地和海洋档案进行比较。对历史数据的分析表明，埃尔西诺湖是记录南加州气候变化的绝佳地点。对湖最深处盆地的2个岩心的初步研究表明，全新世沉积物层序相对较厚（~10m/ 9000年-基于21个AMS 14C日期），连续，沉积物不连续的证据很少。对若干沉积学参数的分析表明，2个岩心在厘米尺度上的变化是一致的。这笔拨款支持使用已建立的气候敏感代理方法对岩心沉积物进行进一步分析。迄今为止，对两个深盆地岩心进行了连续1cm的质量磁化率、总有机质和总碳酸盐分析。这项研究资助主要集中在两个额外的分析：粒度（湖盆和流域沉积物动力学的代表）和d18O（方解石）和d13C（方解石）（分别代表湖泊水文收支和湖泊/流域生产力）。结合其他来自北美西部和太平洋的古气候记录，埃尔西诺湖记录将被用来更好地描述北美西部全新世气候变化的演变和时空格局。此外，该记录将提供全新世自然气候变化的基线，南加州水管理组织（资助了最初的研究）可以以此为基础评估当前的水管理政策。这一记录也将有助于评估水文系统对一系列气候条件的敏感性。本研究的知识价值将为在局部和区域尺度上表征和理解全新世气候变率提供重要信息。这项研究也将有助于回答有关全新世气候演化及其与更大尺度海洋-大气动力学关系的几个重要问题。这项工作更广泛的影响包括研究经验和论文准备2名本科生和1名硕士生。这项研究的结果将通过一个互动网站传播给加州河滨县埃尔西诺湖的公民和管理人员，同时还将开发一个实地网站，供加州州立大学富勒顿分校的实验课使用。作为一个RUI和少数民族服务研究所，该研究还将为CSUF科学领域中代表性不足的个人提供研究机会。最后，这项研究将为北美西部地区未来的水资源变化提供社会相关的见解，该地区的水资源管理对未来的社会经济稳定至关重要。

The availability and quality of freshwater in western North America is directly linked to natural climate variability. The ability to determine climate variations on relevant time scales is limited by the short duration of observational and instrumental records. The need for long, high-resolution paleoclimatological records is particularly acute in Southern California, where over 20 million people are vulnerable to climate variability. This grant will develop the first complete terrestrial Holocene climate record for southern California using sediment from Lake Elsinore and compare this record to other well-dated terrestrial and marine archives from the region. Analysis of historical data indicates that Lake Elsinore is an excellent site for recording climate variability for southern California. Preliminary research on 2 drill cores from the lake's deepest basin indicates a relatively thick (~10m/9,000 yrs - based on 21 AMS 14C dates), continuous Holocene sediment sequence with minimal evidence for sediment discontinuities. Analyses of several sedimentological parameters reveal centimeter-scale variability that is consistent between the 2 cores. This grant supports further analysis of the cored sediment using established climate-sensitive proxy methods. To date, mass magnetic susceptibility, total organic matter, and total carbonate have been analyzed at 1cm contiguous intervals for both deep basin cores. This research grant focuses on two additional analyses: grain size (a proxy for lake basin and drainage basin sediment dynamics) and d18O(calcite) and d13C(calcite) (proxies for lake hydrologic budget and lake/drainage basin productivity, respectively). In conjunction with other paleoclimate records from western North America and the Pacific Ocean, the Lake Elsinore record will be used to better describe the evolution as well as the spatial and temporal patterns of Holocene climate variability over western North America. Furthermore, this record will provide a baseline of Holocene natural climate variability from which Southern California water management organizations - whom funded the initial research - can assess present water management policies. This record will also help to assess the sensitivity of the hydrologic system to a range of climate conditions.The intellectual merit of this study will provide critical information for characterizing and understanding Holocene climate variability on a local and regional scale. This research will also help to answer several important questions regarding Holocene climate evolution and its relationship to larger-scale ocean-atmosphere dynamics. The broader impacts of this work include research experience and thesis preparation for 2 undergraduate students and 1 M.Sc. student. The results of this study will be disseminated to the citizens and managers of Lake Elsinore, Riverside County, California through an interactive web site as well as the development of a field site for use in lab classes at Cal-State Fullerton. As a RUI and Minority Serving Institute, this research will also provide research opportunities for underrepresented individuals in the sciences at CSUF. Lastly, this research will provide socially relevant insight into future water variability in western North America, a region where water resource management is critical to future socio-economic stability.