Collaborative Research: Early-Versus Late-Holocene Drought Variations in the Northern Rocky Mountains

合作研究：落基山脉北部早全新世与晚全新世的干旱变化

• 批准号: 9905262
• 负责人: Lora Stevens-Landon
• 金额: $ 26.61万
• 依托单位: University of Nebraska-Lincoln
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-09-01 至 2003-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9905262&HistoricalAwards=false
• 关键词: Collaborative; Research; Early; Versus; Late

This study proposes to investigate high-frequency drought events in northwestern Montana for two time intervals: 0-2000 and 7000-9000 14C yr BP. The principal goals are to reconstruct the timing, severity, and cyclicities of shifts in effective moisture so that we may address the following questions: 1) Are drought frequencies correlative in time with known solar and/or oceanic-atmospheric frequencies? 2) Does the frequency of drought change over the last 10 ka BP and are these changes correlative with changes in the climatic boundary conditions? 3) Does the timing of drought in the Northwest have a defined relationship to that of adjacent regions?Three climatic proxies preserved in lake sediments-- the d18O of carbonates, diatom assemblages, and charcoal-will be used to answer these questions. The combined use of d18O and diatoms potentially provides an innovative technique for estimating the severity, as well as the seasonal timing of drought. The addition of charcoal analyses permits the study the effects of drought on both aquatic and terrestrial ecosystems. The study aims to reconstruct high-frequency climatic variations at decadal to sub-decadal resolution. The records will be dated with a combination of varve counts and multiple 14C dates to ensure as accurate and detailed a chronology as possible. Three sites were chosen for analysis to mediate potential complications caused by local climatic effects in mountainous regions.

本研究拟对美国蒙大拿州西北部0 ~ 2000年和7000 ~ 9000年两个14C yr BP时间区间的高频干旱事件进行研究。主要目标是重建有效湿度变化的时间、严重程度和周期，以便我们可以解决以下问题：1)干旱频率是否与已知的太阳和/或海洋-大气频率相关？2)近10 ka BP的干旱频率是否发生了变化，这些变化是否与气候边界条件的变化相关？3)西北地区的干旱时间是否与邻近地区的干旱时间有明确的关系？保存在湖泊沉积物中的三个气候指标——碳酸盐的d18O，硅藻组合和木炭——将被用来回答这些问题。d18O和硅藻的结合使用可能为估计干旱的严重程度以及季节性时间提供一种创新技术。加上木炭分析，可以研究干旱对水生和陆地生态系统的影响。该研究旨在以年代际至次年代际分辨率重建高频气候变化。这些记录将结合阀门计数和多个14C日期来确定日期，以确保尽可能准确和详细的年表。选择三个地点进行分析，以调解山区局部气候影响引起的潜在并发症。