Collaborative Research: Evaluating Snowlines Across the Tropics - The geomorphic imprint of tropospheric cooling and drying during the Last Glacial Maximum

合作研究：评估热带地区的雪线——末次盛冰期对流层冷却和干燥的地貌印记

• 批准号: 2102947
• 负责人: Alice Doughty
• 金额: $ 3.86万
• 依托单位: University of Maine
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-01-01 至 2024-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2102947&HistoricalAwards=false
• 关键词: Collaborative; Research; Evaluating; Snowlines; Across

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).One of the great unsolved mysteries of Earth science is why the global climate oscillates between glacial periods, when multi-kilometer thick ice sheets spread across North America and northern Europe, and interglacial periods, when the Earth is much warmer and continental ice sheets are restricted to very high latitudes. Due to the integrated nature of the global climate system, unlocking this mystery requires knowledge of the chronologic order in which elements of the climate system change during transitions between glacial and interglacial periods and the magnitude of climate changes across latitudes. This project will leverage new and emerging remotely sensed datasets, including high-resolution satellite imagery and digital topography, to address the magnitude of climate changes in the tropical latitudes. Specifically, the researchers will use remotely sensed data to reconstruct former glacial extents throughout the tropics, where glaciers were restricted to the hard-to-reach highlands of high-elevation mountains. The research will produce a globally consistent dataset which will allow the testing of hypotheses about how much the Earth’s low latitudes cooled during the last glacial period, and how tropical changes play into major climate reorganizations. The project will rely heavily on a team of undergraduate researchers and will collaborate with the U.S. Ice Drilling Program to produce public educational material.The methodological approach is based on the realization that past changes in the global climate system can imprint on the topography of mountains. One of the clearest examples of this phenomenon is the transformation of mountain valleys by erosional patterns beneath glaciers. Glaciers only exist where temperatures are cold enough for year-round ice, so if glaciers leave telltale signs of their former extents in erosional and depositional landforms, then it is possible to calculate the position of the freezing line associated with these glaciers. By creating a global dataset of tropical glacial extents in carefully selected areas, the project will achieve three goals: 1) produce a global estimate of the lower bound of the tropical freezing line during the last glacial period 2) use numerical modeling of a “type example” tropical glacial system (Costa Rica) to evaluate the relationship between the annual freezing line and the elevation of glaciers in the tropics and 3) determine whether the lapse rate (change in temperature with elevation) was steeper during the last glacial period. Achieving these goals will advance the understanding of why the global climate has been subject to cyclic variations during Earth’s recent geologic history.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该奖项的全部或部分资金均根据《2021 年美国救援计划法案》（公法 117-2）提供。地球科学未解之谜之一是，为什么全球气候会在冰川期（数公里厚的冰盖遍布北美和北欧）和间冰期（地球变暖得多且大陆冰盖仅限于极高纬度地区）之间波动。由于全球气候系统的综合性，解开这个谜团需要了解冰期和间冰期过渡期间气候系统要素变化的时间顺序以及跨纬度气候变化的幅度。该项目将利用新兴的遥感数据集，包括高分辨率卫星图像和数字地形，来解决热带纬度地区气候变化的严重程度。具体来说，研究人员将利用遥感数据重建整个热带地区以前的冰川范围，那里的冰川仅限于难以到达的高海拔山脉高地。该研究将产生一个全球一致的数据集，该数据集将允许测试有关地球低纬度地区在末次冰期期间变冷程度以及热带变化如何影响重大气候重组的假设。该项目将在很大程度上依靠本科研究人员团队，并将与美国冰钻计划合作制作公共教育材料。该项目的方法基于这样的认识：全球气候系统过去的变化可能会影响山脉的地形。这种现象最明显的例子之一是冰川下方的侵蚀模式对山谷的改造。冰川只存在于温度足够冷、适合全年结冰的地方，因此，如果冰川在侵蚀和沉积地貌中留下了其以前范围的明显迹象，那么就有可能计算出与这些冰川相关的冰冻线的位置。通过在精心挑选的地区创建热带冰川范围的全球数据集，该项目将实现三个目标：1）对末次冰期期间热带冰河线下限进行全球估计；2）使用“典型”热带冰川系统（哥斯达黎加）的数值模型来评估热带地区年度冰河线与冰川海拔之间的关系；3）确定递减率（变化率）是否会下降。 在末次冰期期间，温度随着海拔的升高而变得更加陡峭。实现这些目标将促进人们对为什么全球气候在地球最近的地质历史中受到周期性变化的理解。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。