Collaborative Research: Evaluating Hydrologic and Ecologic Responses to late-Glacial (9-33ka) Abrupt Climatic Transitions in the Coastal southwest United States

美国西南部沿海地区的气候预测预测，降水的频率和幅度将发生变化，可能会出现整体干旱。尽管模型预测存在不确定性，但很明显，该地区以冬季为主的水文气候学的任何变化，无论是盛宴还是饥荒，都将对这个人口稠密、水资源紧张的地区产生后果。这项建议利用物理(粒度)、生物(花粉)、化学(C：N)和同位素(叶蜡氢同位素)分析，开发了加利福尼亚州埃尔西诺湖十年到亚百年尺度的连续沉积档案。这一独特的西南沿海陆地遗址具有特殊的分辨率和档案连续性，为评估晚期冰期(9-33ka)气候突变期间的水文和生态变化提供了无与伦比的机会。将使用多样化的多代理方法来描述岩芯的特征，以捕捉大规模的晚期冰川过渡，包括每密尔100的叶蜡D/H位移、可变径流的粒度证据以及集水区植被变化的孢粉学证据。埃尔西诺湖的特殊档案以连续沉积、高沉积速率和使用离散有机材料进行非常高分辨率的放射性碳年龄控制的能力为特征。除了代表过去陆地环境变化的高质量档案外，埃尔西诺湖沉积物还将能够与已公布的海洋重建数据进行拟议的对比，包括太平洋海洋表面温度的本地和远端海洋记录，以及大西洋海洋表面温度记录和子午线翻转环流证据，以评估该区域水文和生态变化的驱动原因。该团队将专注于全球气候突变，包括海因里希事件1-3，以及进入和离开博林-阿勒罗德和年轻的仙女座的转变。尽管这些转变不同于预测的人为气候变化，但它们提供了大规模、突然的转变，能够最大限度地洞察强迫-反应关系。工作假设是，水文变化和生态变化是紧密同步的，并对冰川晚期至全新世早期的局部和全球气候突变做出响应。问题是这些地方的反应有多大，有多快，以及可能对未来产生什么影响。首席调查机构加州州立大学富勒顿接触到大量少数族裔，特别是西班牙裔学生。该提案聘请了两名女性联合调查员，其中一人是早期职业助理教授。这项拟议的研究将为三个机构的研究生和本科生研究提供培训和研究机会，重点是建立分析和解释技能集。这项研究还将提供第一个以陆地为基础的、十年至亚百年尺度的记录，记录西南沿海植被如何对气候突变做出反应。对过去水文和生态变化的原因、反应和恢复的基线理解的发展超越了古气候领域，对生态学家、自然资源保护者和与加州植物生物多样性热点有关的政策决策具有重要意义。

Climate projections for the coastal southwestern United States predict a change in the frequency and magnitude of precipitation, perhaps with an overall drying. Despite the uncertainty in model projections, it is clear that any change to the region's winter dominated, "feast or famine" hydroclimatology will have consequences for the highly-populous, water-stressed region. This proposal develops a decadal to subcentennial scale, continuous sedimentary archive from Lake Elsinore, California using physical (grain size), biological (pollen), chemical (C:N), and isotopic (leaf wax hydrogen isotopes) analyses.Characterized by exceptional resolution and archive continuity, this unique terrestrial site in the coastal southwest offers an unparalleled opportunity to evaluate hydrologic and ecologic change across abrupt climatic transitions during the late Glacial period (9-33ka). The cores will be characterized using a diverse, multi-proxy approach to capture large magnitude, late Glacial transitions, including leaf wax D/H shifts of 100 per mil, grain size evidence for variable run-off, and palynological evidence for changes in catchment vegetation. Lake Elsinore's exceptional archive is characterized by continuous deposition, high sedimentation rates, and the capacity for very high resolution radiocarbon age control using discrete organic material. Beyond representing a high quality archive of past terrestrial environmental change, Lake Elsinore sediments will enable proposed correlations with published marine reconstructions including local and distal marine records of Pacific sea surface temperatures (SSTs), as well as Atlantic SSTs and evidence for Meridional Overturning Circulation in order to assess the driving causes of the region's hydrologic and ecologic change. The team will focus on global abrupt climatic transitions including Heinrich events 1-3, and the transitions into and out of the Bolling-Allerod and the Younger Dryas. Although these transitions differ from the projected anthropogenic climate change, they offer large magnitude, abrupt transitions capable of providing maximum insights into forcing-response relationships. The working hypothesis is that hydrologic changes and ecologic shifts are closely in step and responding to local and global abrupt climatic transitions in the late Glacial to early Holocene. The questions are how much and how fast are these local responses demonstrated, and what might be the implications for the future.The lead investigator's institution, Cal State Fullerton, reaches a large number of minority, and especially Hispanic students. The proposal engages two female co-investigators, one of whom is an early career Assistant professor. The proposed study will provide training and research opportunities for graduate and undergraduate research at three institutions, with a focus on building the analytical and interpretative skill sets.This research will also provide the first terrestrially-based, decadal to subcentennial scale record of how the vegetation of the coastal southwest responds to abrupt climatic transitions. The development of a baseline understanding of the causes, responses, and recovery of past hydrologic and ecologic change is of interest beyond the paleoclimate field with implications for ecologists, conservationists, and policy decisions pertaining to the California Floristic Biodiversity Hotspot.