Doctoral Dissertation Research: Changing Spatial Patterns of Rocky Mountain Snowpack During the Holocene and Their Effects on Ecological Boundaries

博士论文研究：全新世落基山积雪的空间格局变化及其对生态边界的影响

• 批准号: 0623442
• 负责人: Bryan Shuman
• 金额: $ 1.2万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-01-15 至 2010-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0623442&HistoricalAwards=false
• 关键词: Doctoral; Dissertation; Research; Changing; Spatial

Snowpack is a vital water resource in the West, but little is know about its variation beyond the past 60 years. Vegetation and lake level studies from the Rocky Mountains indicate significant changes in precipitation regimes, including changes in snowpack, during the past 11,000 years. In order to examine the patterns of precipitation change in the past, and to provide long-term context for understanding present and future changes, this doctoral dissertation research project aims to quantify millennial-scale changes in seasonal precipitation patterns over the Holocene and their relation to ecological changes at several sites across the West. Multiple lines of independent evidence from fossil pollen, hydrogen and oxygen isotopes, and lake sediment stratigraphies will be used to reconstruct past moisture, vegetation and fire regime gradients. A survey of modern lake water isotopic values across a gradient of seasonal precipitation regimes will provide a baseline for understanding the sensitivity of lake isotopic budgets to changes in seasonal contributions of precipitation. This baseline will be used to calibrate a hydrologic model that includes lake water and isotopic budgets that will aid in quantifying paleoclimatic records of snowpack. Water budgets, informed by past lake-level data, will determine estimates of overall moisture availability. Isotopic budgets will inform estimates of the contributions of seasonal precipitation to lake-water volume, and of the amount of evaporation. By investigating variations in the spatial patterns of seasonal precipitation over the past 11,000 years in the Rocky Mountains, we will examine the linkages between snowpack change, atmospheric circulation, ecotone shifts, and fire regimes. Annual snowpack is the largest reservoir of fresh water in the West, study results will be especially crucial for evaluating water resources and the possible effects of future climate change in the West. Research sites span key spatial gradients in modern precipitation to investigate the stability of these gradients over time in order to provide a context for understanding recent changes in spatial and volumetric distribution of snowpack in the West. Study results will also evaluate the potential effect of snowpack changes on forest distributions and wildfire regimes. Because the Holocene contains periods of different El-Nino frequency and intensity than today and periods that were likely warmer than today, studying Holocene snowpack distribution may reveal insight into the potential for future changes and their ecological effects. As a Doctoral Dissertation Improvement award, this project will enable a strong student to develop a promising and independent career.

在西部，积雪是一种重要的水资源，但人们对过去60年来积雪的变化知之甚少。落基山脉的植被和湖泊水平研究表明，在过去的11000年里，降水制度发生了重大变化，包括积雪的变化。为了研究过去的降水变化模式，并为理解现在和未来的变化提供长期背景，本博士论文研究项目旨在量化全新世季节降水模式的千年尺度变化及其与西方几个地点的生态变化的关系。来自化石花粉、氢和氧同位素以及湖泊沉积物地层的多条独立证据将用于重建过去的湿度、植被和火灾梯度。跨季节降水制度梯度的现代湖泊水同位素值调查将为理解湖泊同位素收支对降水季节贡献变化的敏感性提供基线。该基线将用于校准包括湖水和同位素预算在内的水文模型，这将有助于量化积雪的古气候记录。根据过去的湖泊水位数据，水量预算将决定对总体水分可用性的估计。同位素预算将为季节性降水对湖泊水量和蒸发量的贡献的估计提供信息。通过研究落基山脉过去11000年季节性降水空间格局的变化，我们将研究积雪变化、大气环流、过渡带转移和火灾制度之间的联系。年积雪是西部最大的淡水储存库，研究结果对于评价西部水资源和未来气候变化可能产生的影响尤为重要。研究地点跨越了现代降水的关键空间梯度，以研究这些梯度随时间的稳定性，从而为理解西部积雪空间和体积分布的近期变化提供背景。研究结果还将评估积雪变化对森林分布和野火状况的潜在影响。由于全新世包含的厄尔尼诺频率和强度与今天不同的时期，以及可能比今天更温暖的时期，研究全新世积雪分布可能会揭示未来变化的潜力及其生态影响。作为博士论文进步奖，这个项目将使一个强大的学生发展一个有前途的和独立的职业生涯。