Collaborative Research: Holocene Drought Cycles and Impacts on the Northern Great Plains

这项研究将利用对大平原北部封闭盆地湖泊岩心的高分辨率分析来确定全新世干旱的频率、强度、持续时间、周期性和同步性，并研究植被和火对干旱的反应。由于大平原北部的植被和湖泊对干旱高度敏感，这一地区提供了一个记录美国大陆中部十年至世纪尺度气候周期的绝佳机会。工作假设是，来自单一地点的干旱信号是地区性的，整个地区的干旱是同步的。为了验证这一假设，这项研究将利用湖泊沉积物矿物学、化石花粉、木炭的碳同位素和木炭丰度来详细重建大平原北部十年尺度的干旱周期。这将有助于评估大陆中部气候和北大西洋区域之间的遥相关，该区域最近的研究已将百年至千年尺度的气候振荡与太阳辐射的变化联系起来。这项研究有可能在物理和社会科学领域产生广泛影响。对大气模型预测的大平原北部干旱影响的评估需要了解自然干旱的可变性。来自古科学的证据表明，20世纪的干旱(例如沙尘暴)并不能提供对最近发生的严重干旱范围的看法。历史证据不完整，古科学数据尚未在适当的时间和空间尺度上收集起来，以评估过去干旱的强度、周期性和影响。

This study will utilize high-resolution analysis of cores from closed-basin lakes in the northern Great Plains to determine the frequency, intensity, duration, periodicity, and synchrony of droughts during the Holocene and to examine how vegetation and fire responded to drought. Since vegetation and lakes in the Northern Great Plains are highly sensitive to drought, this region offers an extraordinary opportunity to document decadal- to-century scale climate cycles in the mid-continental United States. The working hypothesis is that the signal of drought from a single site is regional and that droughts were synchronous across the region. To test this hypothesis, the study will utilize lake-sediment mineralogy, fossil pollen, carbon isotopes of charcoal, and charcoal abundance to develop detailed reconstruction of drought cycles from the Northern Great Plains at a decadal scale. This will facilitate evaluation of the teleconnections between mid-continental climate and the North Atlantic region, where recent investigations have linked century to millennial scale climate oscillations to variations in solar irradiance. This research has the potential for broad impact in range of physical and social sciences. Assessment of drought impacts forecast by atmospheric models for the Northern Great Plains requires understanding of natural drought variability. Evidence from paleoscience suggests that 20th century droughts (e.g., the Dust Bowl) do not provide perspective on the range of severe droughts that have occurred in even the recent past. Historical evidence is incomplete and paleoscience data have not yet been assembled at appropriate temporal and spatial scales to assess the intensity, periodicity, and impacts of past droughts.