Collaborative Research: Holocene Drought in the North American Interior

这项研究将检验关于北美大陆内陆两个干旱易发地区(大平原北部和落基山脉北部)在数十年到千年时间尺度上发生重大干旱的原因和空间模式的几个假说。将从保存在区域湖泊沉积物中的无机和有机地球化学记录中为大平原北部生成跨越整个全新世的十年分辨率降水变化的第一个定量重建。此外，这项研究还将开发一种相对较新的大陆环境的地球化学指标，特别是使用烯酮来重建盐湖的温度变化。智力价值高分辨率的古气候数据表明，在过去的两千年里，北美西部大部分地区经历了比20世纪干旱更持久的大范围严重干旱。目前还不清楚是什么导致了这些所谓的巨灾，因为只有少数高分辨率的大陆古气候记录跨越了过去1000到2000年。这项拟议的研究将比较从大平原北部延伸到整个全新世的高分辨率(十年制)记录与落基山脉北部的记录。跨越数千年的记录的产生将使人们能够评估大范围边界条件的变化如何影响数十年干旱的频率，例如以全新世早期和晚期为特征的季节性日照差异。重建的中部大陆主要干旱的长期时间序列将与太平洋和北大西洋海面温度记录进行比较，以评估1)落基山脉北部和大平原北部是否对大西洋和太平洋的变率具有不同的敏感性，以及2)干旱与潜在海洋强迫之间的关系是否随时间保持不变。这项研究还将开发和应用一种相对新的、功能强大的大陆环境中温度重建的地球化学指标，这有可能极大地提高我们解释过去气候和水文响应的能力。广泛影响了解过去与严重持续干旱相关的因素是有益的，因为它使评估当前的水资源管理计划是否基于对气候的自然长期变异性的正确理解。为了加强公众和直接受干旱影响的人们的科学了解，这项研究将为蒙大拿州东部的一个新的州立公园制作一个展览，该公园位于初级湖岸，将在这个项目中进行研究。展览将介绍如何利用湖泊沉积物来生成气候和景观演化史，以及对该湖进行的研究所提出的关于干旱历史的见解。此外，三名研究生将接受社会相关性跨学科研究的培训。

This research will test several hypotheses about the causes and spatial pattern of major drought at multi-decadal to millennial time scales in two drought prone regions of the North American continental interior: the northern Great Plains and northern Rocky Mountains. The first quantitative reconstruction of precipitation variation at decadal resolution that spans the entire Holocene will be generated for the northern Great Plains from inorganic and organic geochemical records preserved in regional lake sediments. In addition, the research will develop a relatively new geochemical indicator for continental settings, specifically the use of alkenones to reconstruct temperature variation in saline lakes.Intellectual MeritHigh-resolution paleoclimatic data suggest that, during the last two millennia, much of western North America experienced widespread severe drought that was more persistent than the droughts of the 20th century. It is unclear what produces these so-called megadroughts, because only a handful of high-resolution continental paleoclimatic records span more than the last 1000 to 2000 years. The proposed research will compare high resolution (decadal) records that extend through the entire Holocene from the northern Great Plains with records from the northern Rocky Mountains. The generation of records that span many millennia will enable an assessment of how the frequency of multi-decadal drought is influenced by changes in large-scale boundary conditions, such as the seasonal insolation differences that characterize the early versus late-Holocene. The long reconstructed time series of major drought in the mid continent will be compared with Pacific and North Atlantic sea-surface temperature records to evaluate 1) whether the northern Rockies and northern Great Plains are differentially sensitive to Atlantic versus Pacific variability, and 2) whether the relationship between drought and potential oceanic forcing is stationary through time. The research also will develop and apply a relatively new and powerful geochemical proxy for temperature reconstruction in continental settings, which has the potential to greatly improve our ability to interpret past climates and hydrologic responses.Broader ImpactsUnderstanding the factors associated with severe persistent drought in the past is of societal benefit, because it enables an assessment of whether or not current water management plans are based on a sound understanding of the natural long-term variability of climate. To enhance the scientific understanding of the public and the people directly impacted by drought, the research will create an exhibit for a new state park in eastern Montana, located on the shores of the primary lake to be studied in this project. The exhibit will describe how lake sediments can be used to generate a history of climate and landscape evolution and the insights about drought history suggested by research carried out on this lake. In addition, three graduate students will receive training in interdisciplinary research of societal relevance.