Collaborative Research: Evaluating hydrologic and ecologic responses to late-Glacial (9-33ka) abrupt climatic transitions in the coastal southwest United States

对美国西南部沿海地区的气候预测预测，降水的频率和强度都会发生变化，可能还会出现全面的干旱。尽管模式预测存在不确定性，但很明显，该地区冬季主导的“盛宴或饥荒”水文气候学的任何变化都将对人口众多、水资源紧张的地区产生影响。本研究利用物理（粒度）、生物（花粉）、化学（C:N）和同位素（叶蜡氢同位素）分析了加利福尼亚埃尔西诺湖的十年至次百年的连续沉积档案。西南沿海的这一独特的陆地遗址以其出色的分辨率和档案连续性为特征，为评估晚冰期（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。这些岩心将使用多样化的、多代理的方法来表征，以捕捉大尺度的晚冰期转变，包括每毫升100次的叶蜡D/H变化，径流变化的粒度证据，以及流域植被变化的孢粉证据。埃尔西诺湖的特殊档案的特点是连续沉积，高沉积速率，以及使用离散有机材料进行非常高分辨率放射性碳年龄控制的能力。除了代表过去陆地环境变化的高质量档案外，埃尔西诺湖的沉积物将使人们能够提出与已发表的海洋重建的相关性，包括太平洋表面温度（SSTs）的本地和远端海洋记录，以及大西洋SSTs和经向翻转环流的证据，以评估该地区水文和生态变化的驱动原因。该团队将重点关注全球气候突变，包括海因里希事件1-3，以及进入和退出博林-阿勒罗德和新仙女木时期的过渡。虽然这些转变与预估的人为气候变化不同，但它们提供了大幅度、突然的转变，能够最大限度地深入了解强迫-响应关系。工作假设是，在冰期晚期到全新世早期，水文变化和生态变化是密切同步的，响应着局部和全球气候的突变。问题是这些地方反应的程度和速度，以及对未来可能产生的影响。主要调查机构加州州立大学富勒顿分校（calstate Fullerton）接触了大量少数族裔，尤其是西班牙裔学生。该提案聘请了两位女性共同研究人员，其中一位是早期职业助理教授。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，重点是培养分析和解释技能。这项研究还将提供第一个基于陆地的、年代际到次百年尺度的记录，记录西南沿海的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、响应和恢复的基线理解的发展超出了古气候领域，对生态学家、保护主义者和与加利福尼亚植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 investigators 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.