Doctoral Dissertation Research: Analyzing Tropical Alpine Glacier Dynamics During Middle-Holocene Warming

这个博士论文研究项目将在热带地区的一组山脉中开发过去冰川范围的记录，并将评估该地区和类似地区的冰川对气候条件变化的敏感性，例如交替的温度和降水制度。该项目将提供新的信息和见解，以解决高山热带冰川对气候变化和其他环境条件特别敏感的程度。先前的证据似乎表明，该研究区域的高山冰川在全新世中期持续存在，有证据表明，在这一时期，气温与现在一样温暖，甚至比现在更温暖。该项目有助于评估这些冰川对变暖的敏感性，以便更好地确定过去冰川波动的时间和幅度。通过像这样重建热带地区过去的冰川范围，该项目将提高对影响热带冰川的因素和动力学以及它们对变化环境的敏感性的基本认识。该项目还将提供信息，以便对未来冰川质量损失进行更准确的预测，项目发现将有助于热带地区的规划和发展活动，在热带地区，冰川提供了重要的淡水资源，持续的冰川衰退将直接影响社区的生计和福祉。该项目将通过让本科生参与项目的某些方面，以及在佛蒙特州和新罕布什尔州的小学和中学课堂上进行基于项目的演讲，提供额外的教育和培训好处。作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立研究生涯。热带冰川的持续退缩已被强调为当代地球周围环境条件变化的一种表现，但这些冰川对预测的未来气候条件的敏感性是不确定的。通过这篇论文的研究项目，博士生将通过确定大约8000到4000年前非洲热带东部的冰川范围来提高对热带冰川对温度升高的反应的理解，当时该地区与现在一样温暖或更温暖。该学生将使用详细的地貌图和鲁文佐里山脉冰川沉积物的地表暴露年代来确定当前被称为全新世的间冰期的冰川范围，该间冰期从大约11600年前延伸到现在。她将采用一种表面暴露测年法，该方法依赖于宇宙核素铍-10的测量，铍-10是由于宇宙射线的涌入而在岩石表面随着时间的推移而产生的。该项目将是首个以铍-10为基础的东非热带全新世冰川年表的研究。该学生将把鲁文佐里冰川年表与东非热带其他地区的温度、降水和冰川范围记录进行比较，以评估区域气候条件和冰川波动模式。这些结果将与热带南美洲全新世冰川范围进行比较。确定全球热带地区的冰川在全新世期间是同步波动还是不同步波动，将为评估与全球气候条件变化相关的动力学提供信息。项目结果将推动在未来变暖情景下对冰川进行模拟的努力，从而提供一种方法来检验关于全新世期间在全球范围内传播气候信号的可能机制的假设。

This doctoral dissertation research project will develop records of past glacier extents in one set of mountains in a tropical setting and will assess the sensitivity of glaciers in this and similar regions to changes in climatic conditions, such as alternate temperature and precipitation regimes. The project will provide new information and insights to address the degree to which alpine tropical glaciers are especially sensitive to changing climatic and other environmental conditions. The study region is one for which previous evidence seemed to indicate that alpine glaciers persisted during the middle of the Holocene Epoch, a period when evidence indicates that temperatures were as warm as or warmer than the present time period. The project helps to assess the sensitivity of these glaciers to warming temperatures in order to better ascertain both the timing and magnitude of past glacier fluctuations. By reconstructing past glacier extents in tropical regions like this, this project will improve basic understanding about the factors and dynamics that affect tropical glaciers as well as their sensitivity to a changing environment. The project also will provide information that will yield more accurate predictions of future glacier mass loss, project findings will facilitate planning and development activities in tropical regions, where glaciers provide crucial freshwater resources and ongoing glacier recession will impact directly the livelihoods and wellbeing of communities. The project will provide additional education and training benefits by engaging undergraduate students in some facets of the project and through presentations based on the project in elementary and secondary school classrooms in Vermont and New Hampshire. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.The ongoing retreat of tropical glaciers has been highlighted as one manifestation of contemporary change in environmental conditions around the Earth, but the sensitivity of these glaciers to projected future climate conditions is uncertain. Through this dissertation research project, the doctoral student will improve the understanding of tropical glacier response to warmer temperatures by determining the extents of glaciers in tropical eastern Africa over a period roughly 8,000 to 4,000 years ago, when the region was as warm as or warmer than at present. The student will use detailed geomorphic mapping and surface exposure dating of glacial deposits in the Rwenzori Mountains to determine glacier extents during the current interglacial period known as the Holocene Epoch, which extends from about 11,600 years ago to the present. She will employ a surface-exposure dating method that relies on measurements of the cosmogenic nuclide beryllium-10, which is produced in rock surfaces over time due to the influx of cosmic rays. The project will be the first study to develop a beryllium-10-based chronology of Holocene glacier extents in tropical eastern Africa. The student will compare the Rwenzori glacier chronology with records of temperature, precipitation, and glacier extents from other locations in tropical East Africa in order to assess the regional climate conditions and patterns of glacier fluctuations. These results will be compared with Holocene glacier extents in tropical South America. Determining whether glaciers across the global tropics fluctuated synchronously or asynchronously during the Holocene Epoch will provides information for evaluating the dynamics associated with changing global climatic conditions. Project results will advance efforts to model glaciers within future warming scenarios, thereby providing a means to test hypotheses about the possible mechanisms that transmitted climate signals across the globe during the Holocene Epoch.