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

这项研究建议调查蒙大拿州西北部两个时间间隔的高频干旱事件：0-2000和7000-9000 14C yr BP。主要目标是重建有效湿度变化的时间、严重程度和周期性，以便我们可以解决以下问题：1)干旱频率在时间上是否与已知的太阳和/或海洋-大气频率相关？2)过去10 ka BP干旱频率是否变化，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、硅藻组合和木炭的d18O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和季节性时间提供了一种创新的技术。通过添加木炭分析，可以研究干旱对水生和陆地生态系统的影响。这项研究旨在重建十年到亚十年分辨率的高频气候变化。这些记录将结合VVE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。选择了三个地点进行分析，以调解山区局部气候效应造成的潜在并发症。

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.