COLLABORATIVE RESEARCH: Global Change and the Terrestrial Paleoclimate Record from Eastern North America: 600,000 years BP to Present

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。智力价值：这笔拨款将支持开发校准的、高分辨率的、绝对定年的稳定同位素和痕量金属时间序列，这些序列来自多个洞穴系统，这些洞穴系统保存在田纳西州东部、西弗吉尼亚州南部到西弗吉尼亚州东北部的N-S样带中。现代区域气候对北大西洋和太平洋海面变率明显敏感，而气候变率，特别是干旱和古干旱的发生，在仪器记录（如AMO、PDO/NPO）和古记录（如Bond-scale cyclicity、8200年事件）中与大尺度海洋和大气模式有关。此外，研究小组将使用一个包括碳循环在内的完全耦合的气候模型，研究新仙女木期开始时陆地和海洋对气候变化的地球化学反应。整合后，这项工作将产生一个独特的数据产品，用于评估该地区至少最近六个冰期/间冰期旋回的气候变化的时间、幅度和潜在原因。该项目基于洞穴的部分的具体成果是一个年代确定的复合时间序列，可用于评估气候变率的模式和时间尺度，并在近海洋和更远的洞穴（如中国、阿曼）和冰芯记录的背景下，评估造成气候不稳定和模式转变的潜在驱动机制。还将比较N-S样带各个站点的时间序列，以评估气候边界变化的重要性。对研究样带43个洞穴的年代学控制（230Th年龄）表明，通过海洋同位素阶段15 （~600 kyr BP）重建区域气候变化具有特殊的潜力。230年的时间序列将有助于在人类活动的时间尺度上定义气候变化。具体来说，整合来自多个地点的几个高分辨率（多十年尺度）全新世洞穴记录将1)确定过去一万年中气候突变（如8200年事件）的时间，2)解决气候突变的基础。此外，对晚更新世洞穴化石的类似研究将使我们更全面地了解过去的特定气候模式是如何演变的，当时的气候可能与今天的（MIS-2、6、8、10、12、14）相似（例如，MIS-5、7、9、11、13、15）。利用对洞穴滴水（del-18O、del-13C、痕量金属）、洞穴环境（温度、湿度、二氧化碳分压）和洞穴上方大气/水文条件的同位素/地球化学校准研究结果，将加强对晚第四纪气候历史的解释。该项目建模部分的结果将有助于理解地球化学反馈以及在气候快速变化时期（如新仙女木期）可能放大或稳定的因素。提出的研究解决了P2C2的关键倡议，包括1)评估与大尺度耦合气候系统有明显联系的区域对气候模式变化的敏感性和响应，2)评估对突发和极端气候事件的响应，以及3)数据模型综合。更广泛的影响：拟议的研究将定义北美东部大西洋中部/阿巴拉契亚地区过去~60万年的气候变化历史，这是一个人口密集的国家重要地区。该项目旨在提供有意义的实验室和实地指导/实习机会，将本科生与研究生水平和三所大学的教师导师结合起来。pi代表三个不同的研究小组，致力于招募代表性不足的群体，包括女性和少数民族。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Intellectual Merit: This grant will support the development of calibrated, highly-resolved, and absolute-dated stable isotopic and trace-metal time series from multiple speleothems preserved in multiple cave systems along a N-S transect from East Tennessee, through southern West Virginia, to northeastern West Virginia. Modern regional climate is demonstrably sensitive to sea-surface variability of the North Atlantic and Pacific Oceans, and climate variability, in particular the occurrence of drought and paleo-drought, has been linked to large-scale oceanic and atmospheric patterns in the instrumental record (e.g., AMO, PDO/NPO) and in the paleo-record (e.g., Bond-scale cyclicity, 8200-year event). In addition, the team will investigate the geochemical response on land and in the ocean to climatic changes at the onset of the Younger Dryas, using a fully coupled climate model including a carbon cycle. When integrated, the work will yield a unique data product that evaluates the timing, magnitude, and underlying causes for climatic change in the region for at least the last six glacial/interglacial cycles.The specific deliverable for the speleothem-based portion of the project is a well-dated composite time series that can be used to assess the modes and timescales of climate variability, and, in the context of proximal marine and more distal speleothem (e.g., China, Oman) and ice-core records, evaluate the potential driving mechanisms responsible for climate instability and mode-shifts. Time series from individual sites along the N-S transect will also be compared in order to assess the importance of shifts in climatic boundaries. Geochronological control (230Th ages) on 43 speleothems from the study transect demonstrate that exceptional potential exists for reconstructing regional climate change back through Marine Isotope Stage 15 (~600 kyr BP). The 230Th-dated time series will help define climate shifts on timescales of human activity. Specifically, the integration of several highly-resolved (multidecadal-scale) Holocene speleothem records from multiple sites will 1) define the timing of, and 2) resolve the basis for abrupt climate change (e.g., 8200-year event) during the past ten millennia. Furthermore, similar studies of late Pleistocene speleothems will yield a more comprehensive understanding of how specific climate modes evolved in the past when climate was presumably similar to (e.g., MIS-5, 7, 9, 11, 13, 15) or different from (MIS-2, 6, 8, 10, 12, 14) today. Interpretation of the late Quaternary climate history will be strengthened using results from a proposed isotopic/geochemical calibration study of cave drip waters (del-18O, del-13C, trace-metal), cave environment (temperature, humidity, pCO2), and the atmospheric/hydrological conditions above the cave. Results from the modeling-part of the project will contribute to the understanding of geochemical feedbacks and possible amplifying or stabilizing factors at times of rapid climate change, such as the Younger Dryas.The proposed study addresses key initiatives of P2C2, including 1) assessment of sensitivity and response to climate mode changes in a region with demonstrable linkages to large-scale coupled climate systems, 2) assessment of responses to abrupt and extreme climate events, and 3) data-model synthesis.Broader Impacts: The proposed research will define the history of climate change during the last ~600,000 years for the mid-Atlantic/Appalachian region of eastern North America, a highly-populated region of national importance. The project is designed to provide meaningful lab- and field-based mentorship/traineeship opportunities that couple undergraduates with graduate-level and faculty mentors across three universities. The PIs represent three diverse research groups committed to recruitment of underrepresented groups, including females and minorities.