RUI: Collaborative Research: Glaciation and Climate Change in the Rocky Mountains During the Last Glacial Maximum and the Subsequent Deglaciation

在最后一次更新世冰期，北美西部落基山脉有大量的山地冰川，这些冰川的地质记录提供了在最后一次冰盛期期间和之后气候变化的戏剧性证据。这项研究将在美国落基山脉地区更新世山脉冰川年代学的基础上进行补充，并利用这些年代学来模拟过去的气候变化。该项目使用实地考察和分析方法来解决两个广泛目标：(1)确定从蒙大拿州北部到新墨西哥州中南部的样带，维持落基山脉冰川在最后更新世的最大范围内所必需的现代气候变化；(2)确定随后冰川衰退的时间和速度，以及推动这种衰退所需的气候变化的幅度和速度。第一个目标涉及八个研究区域的额外冰川测绘和年代学，利用宇宙成因的铍-10表面暴露测年，以限制最后一次冰盛期冰川的时间和范围。冰川物质平衡和冰流的数值模型将能够确定足以产生观测到的冰川范围的气候变化的性质和程度。第二个目标涉及在八个研究区域中的四个区域进行额外的表面暴露年代测定，以限制最大林分后冰川衰退的时间和速度，并允许对导致冰川衰退的气候变化进行建模。这项研究的结果将包括最后一次更新世冰川和随后的冰川消融的区域综合冰川气候重建，最后一次冰川最大值时间表观变化的气候意义的评估，以及山脉冰川运动年代学的改进。这种高分辨率冰川建模和宇宙成因-放射性核素测年方法的应用将提供对落基山脉地区气候变化历史的洞察。感兴趣的时间间隔是最后一次冰川最大时期(全球冰量最大的时间间隔)和随后向当前暖期的过渡，后者发生在大约6000年后。这一过渡是全球变暖的主要时期，在此期间，美国西部的大气环流发生了重大变化，以应对冰盖缩小、到来的太阳辐射增加和大气二氧化碳水平上升。正如古气候模型所表明的那样，气流的这种变化无疑带来了区域降水模式的变化。这项研究的结果将评估这些模型在表示过去降水模式方面的准确性，并可能为对落基山脉地区未来降水变化的模型预测的准确性提供洞察，该地区对有限的水资源的需求继续增长。

Mountain glaciers were numerous in the Rocky Mountains of western North America during the last Pleistocene glaciation, and the geologic record of these glaciers provides dramatic evidence of climatic changes during and following the Last Glacial Maximum. This research will build upon and augment the Pleistocene mountain glacial chronologies in the U.S. Rocky Mountain region, and use these chronologies to model past climate changes. The project uses both field and analytical methods to address two broad objectives: (1) to determine the changes from modern climate that would be necessary to sustain Rocky Mountain glaciers at their last Pleistocene maximum extents, along a transect from northern Montana to south-central New Mexico, and (2) to determine the timing and rate of subsequent ice recession, and the magnitudes and rates of climate change necessary to drive that recession. The first objective involves additional glacial mapping and chronology in eight study areas, making use of cosmogenic beryllium-10 surface-exposure dating to constrain the timing and extent of glaciers during Last Glacial Maximum. A numerical model of glacier mass balance and ice flow will allow determination of the character and magnitudes of climatic change sufficient to produce the observed glacial extents. The second objective involves additional surface-exposure dating in four of the eight study areas to constrain the timing and rates of ice recession following its maximum stand, and to allow modeling of the climate changes that caused the recession. The results of this research will include a regional synthesis of glacier-climate reconstructions for the last Pleistocene glaciation and the subsequent deglaciation, an assessment of the climatic significance of the apparent variability in the timing of the Last Glacial Maximum, and an improvement in the chronology of mountain glacier movements.This application of high-resolution glacier modeling and cosmogenic-radionuclide dating methods will provide insight into the history of climate change in the Rocky Mountain region. The time interval of interest is the Last Glacial Maximum (the interval of maximum global ice volume) and the subsequent transition to the present warm period, the latter occurring over approximately 6000 years. This transition was an interval of major global warming, during which substantial changes in atmospheric circulation occurred in the western United States in response to shrinking ice sheets, increased incoming solar radiation, and rising atmospheric carbon dioxide levels. Such changes in airflow undoubtedly brought about changes in regional precipitation patterns, as is suggested by paleoclimate models. The results of this research will assess the accuracy of such models in representing precipitation patterns of the past, and may also provide insight into the accuracy of model predictions of future precipitation changes in the Rocky Mountains region, an area where demand for limited water resources continues to grow.