Doctoral Dissertation Research: Deciphering Spatially and Temporally Complex High-Latitude Landscapes

北极和南极的高纬度地貌包含了世界上最大的冰川和冰盖如何对过去的气候变化做出反应的证据，并记录了冰川如何侵蚀和运输沉积物和养分。这一博士论文研究项目将考察格陵兰西北部的一片地区，作为一个天然实验室，可以用来研究数万到数十万年时间尺度上的高纬度景观演变。这位博士生将分析在图勒地区不同但相邻的地区沉积的两个不同的冰川沉积物单位，以确定每个沉积单位是如何在空间和时间上演变的，并将这些洞察力用作了解冰川形成的高纬度地区(包括北美北部和其他高纬度地区)的景观演变和沉积物运输的模型。该项目将提供有关过去冰盖进退时间的有价值的新信息。它将有助于解决冰川冰是否起到了侵蚀作用的问题，并将加强对形成高纬度地貌的复杂过程的科学理解。将通过NOAA古气候学数据库向其他研究人员提供宇宙学数据，并将通过学术和大众媒体传播项目成果，以扩大可能受益于将产生的新见解和信息的个人范围。作为博士论文研究改进奖，该奖项还将为有前途的学生建立强大的独立研究事业提供支持。作为本项目重点的高纬度景观是由冰川进退的循环模式塑造的。在冰川时期，当冰盖膨胀时，地貌可以被冰川冰深度侵蚀和雕刻(如果冰处于融点，并且有液态水可用)，或者保存在非侵蚀性冰川冰下(如果冰低于融点并冻结在床上)。在间冰期，当冰盖缩小时，风化作用通过风、水和冻融作用使物质移动来改变地貌。随后较小的冰层推进可能只覆盖部分地貌，造成不同年龄和历史的表面并列在一起的地理位置。这位博士生将通过分析三种稀有同位素：铍-10、铝-26和碳-14，重建图勒地区复杂的景观历史。只有当岩石裸露且没有被冰川覆盖时，这些同位素才会在岩石表面缓慢积累。对岩石表面这些同位素浓度的分析将提供有关该景观的年龄和暴露历史的信息。

High-latitude landscapes in the Arctic and Antarctic contain evidence of how the world's largest glaciers and ice sheets have responded to past changes in climate, and they document how glaciers erode and transport sediments and nutrients. This doctoral dissertation research project will examine an area of northwestern Greenland as a natural laboratory that can be used to study high-latitude landscape evolution on timescales of tens to hundreds of thousands of years. The doctoral student will analyze two distinct units of glacial sediments that have been deposited in different but adjacent areas in the Thule region in order to determine how each of the sedimentary units has evolved over space and time and use these insights as a model for understanding landscape evolution and sediment transport in glaciated high-latitude regions, including locations in northern North America and other high-latitude landscapes where similar processes are functioning. The project will provide valuable new information about the timing of past episodes of ice sheet advance and retreat. It will help address the question of whether glacial ice has behaved as an agent of erosion, and it will enhance scientific understanding of the complex processes that shape high-latitude landscapes. Cosmogenic data will be made accessible to other researchers via the NOAA paleoclimatology database, and project findings will be disseminated through both scholarly and popular media in order to broaden the range of individuals who may benefit from the new insights and information that will be generated. 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 high-latitude landscapes that are the focus of this project are shaped by a cyclic pattern of glacial advance and retreat. During glacial periods, when ice sheets expand, the landscape can either be deeply eroded and sculpted by glacial ice (if the ice is at the melting point and liquid water is available) or preserved beneath non-erosive glacial ice (if the ice is below the melting point and frozen to the bed). During interglacial periods when ice sheets shrink, weathering modifies the landscape through movement of material by wind, water, and freeze-thaw action. Subsequent smaller ice advances may cover only part of the landscape, creating geographies where surfaces with different ages and histories are juxtaposed. The doctoral student will reconstruct the complex landscape history in the Thule region through the analysis of three rare isotopes: beryllium-10, aluminum-26, and carbon-14. These isotopes build up slowly in rock surfaces only when the rocks are exposed and not covered by glaciers. The analyses of the concentrations of these isotopes in rock surfaces will provide information about the age and exposure history of the landscape.