EAGER - feasibility study in reconstructing Holocene drought history from sediment cores in Fallen Leaf Lake, CA

EAGER - 从加利福尼亚州落叶湖沉积岩芯重建全新世干旱历史的可行性研究

• 批准号: 1247499
• 负责人: Paula Noble
• 金额: $ 1.5万
• 依托单位: Board of Regents, NSHE, obo University of Nevada, Reno
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-15 至 2014-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1247499&HistoricalAwards=false
• 关键词: EAGER; feasibility; study; reconstructing; Holocene

Work in the western US indicates that profound, long-term shifts in patterns of drought throughout the past 10-13,000 years (the Holocene) have had both historic and prehistoric impact on ecosystems and on humans. This grant will develop a long-term drought record from sediment cores in the northern Sierra Nevada, a climatically sensitive region. The project will focus on the alpine portion of the watershed where the effects of winter precipitation deficits are more directly measurable than in terminal lake basins. These effects include lowered lake levels during drought stages, warmer lake temperatures, variations in strength and depth of thermal stratification, and altered biotic structure. In particular, fossil diatom communities in lake sediments are expected to vary in response to drought, and may be used as a indicators of climate change and long-lasting droughts. An excellent diatom record potentially exists in sediments of Fallen Leaf Lake in the Lake Tahoe watershed for use as paleoclimate indicators, with expected multi-decadal to centennial resolution. Preliminary age models on cores taken in 2010 show great promise for developing a detailed chronology. The cores contain a continuous record extending back 13,300 yrs, with sedimentation rates averaging 1.4 mm/year. The team will test whether diatoms in sub-alpine lake sediment can serve as indicators of changes in winter precipitation, and whether changes in diatom, sedimentologic, and selected geochemical indicators can be related to drought conditions during the Medieval Climatic Anomaly and other Holocene long-term droughts. The lake is a good choice because it records large precipitation-driven lake level shifts, and the area's water balance and hydrologic response to drought is measurable. Preliminary data indicates shifts in the number of diatom species associated with a well documented multi-hundred year drought. The team will investigate diatom response to drought conditions by looking at organic geochemistry from discrete samples (% organic matter and C, N isotopes), compound specific geochemistry, and pollen analysis. In addition, the team will conduct X-ray fluorescence scans for biogenic silica and organic matter content at high resolution (0.2-0.5mm). All core proxy data will be cross-correlated using a variety of multivariate and cross spectral techniques. Regional tree-ring climatic records will be used as an independent means of validating hydrological variability.The proposed research has larger impacts to society, and this data should be of interest to aquatic ecologists, natural resource managers, and climate scientists concerned with the long-term response of fresh-water aquatic systems to climatic change. The timing and effects of prolonged drought will also be of interest to anthropologists reconstructing the migrations of Native Americans in response to drier conditions, including the ancestors of the Northern Paiute, the Maidu, the Washoe, the Yokuts, and the West Mono. Further, this effort to better establish diatoms as indicators of climate variation could add to the number of tools used to interpret regional climate change, and its associated impacts on human activities. This project will provide ages and scanning XRF analyses needed to build a quality age model, and establish the basic sedimentologic framework for this set of Holocene cores. This framework is a necessary first step for all of the ongoing paleontologic and geochemical work that is underway with these cores by various graduate students and faculty members. It will also provide the discrete samples needed for the various specialized indicators (diatoms, organic geochemistry, pollen analysis) and analyses necessary for the diatom work. At present, 5 graduate students rely on these cores for their thesis and dissertation research, and will benefit greatly by additional age control, geochemical data, and samples. Cores and data will be archived at the National Lacustrine Core Repository, Minnesota.

美国西部的工作表明，在过去的10 - 13，000年中，干旱模式的深刻，长期的变化（全新世）对生态系统和人类产生了历史性和史前影响。这笔赠款将从内华达州北部塞拉山脉的沉积物岩心（一个对气候敏感的地区）产生长期的干旱记录。该项目将集中于流域的高山部分，其中冬季降水缺陷的影响比末端湖泊盆地更直接。这些影响包括在干旱阶段降低湖泊水平，较高的湖泊温度，强度和热分层深度的变化以及生物结构改变。特别是，预计湖泊沉积物中的化石硅藻群落会因干旱而有所不同，并可以用作气候变化和持久干旱的指标。在太浩湖流域倒下的叶湖的沉积物中可能存在出色的硅藻记录，以用作古气候指标，预期的是多年达到百年纪念。 2010年核心的初步年龄模型显示出开发详细年表的巨大希望。核心包含连续的记录，延长了13,300年，沉积率平均为1.4毫米/年。该团队将测试亚高山湖沉积物中的硅藻是否可以作为冬季降水变化的指标，以及在中世纪的气候异常和其他全新世长期干旱期间，硅藻，沉积学和选定的地球化学指标的变化是否与干旱条件有关。该湖是一个不错的选择，因为它记录了以降水为导向的湖泊水平的偏移，并且该地区对干旱的水平和水文反应是可以衡量的。初步数据表明，与据记录的多年干旱相关的硅藻数量发生了变化。该小组将通过查看离散样品（％有机物和C，N同位素），复合特定地球化学和花粉分析的有机地球化学来研究对干旱条件的硅藻反应。此外，团队将以高分辨率（0.2-0.5mm）进行X射线荧光扫描，以对生物二氧化硅和有机物含量进行X射线荧光扫描。所有核心代理数据都将使用多种多元和跨光谱技术交叉相关。区域树环的气候记录将用作验证水文变异性的独立手段。拟议的研究对社会产生了更大的影响，水生生态学家，自然资源经理和气候科学家应该对与淡水水生系统对气候变化的长期响应有关。人类学家还将对长期干旱的时机和影响进行重建，以应对较干燥的条件，包括北部Paiute的祖先，Maidu，Maidu，Washoe，Yokuts，Yokuts和West Mono。此外，这项努力更好地建立硅藻作为气候变化的指标可能会增加用于解释区域气候变化的工具的数量，以及其对人类活动的相关影响。该项目将提供建立优质年龄模型所需的年龄和扫描XRF分析，并为这套全新世内核建立基本的沉积框架。该框架是所有正在进行的古生物学和地球化学工作的必要第一步，这些核心和地球化学作品正在与各个研究生和教职员工一起与这些核心进行。它还将提供各种专业指标（硅藻，有机地球化学，花粉分析）所需的离散样本以及硅藻工作所需的分析。目前，有5名研究生依靠这些核心进行论文和论文研究，并将受到额外的年龄控制，地球化学数据和样本的大大受益。核心和数据将在明尼苏达州国家湖泊核心存储库中存档。