Tracking Past Ice Sheets with North American River Drainage Basin Captures Induced by Glacial Isostatic Adjustment

通过冰川均衡调整引起的北美河流流域捕获来追踪过去的冰盖

• 批准号: 2120574
• 负责人: Tamara Pico
• 金额: $ 41.34万
• 依托单位: University of California-Santa Cruz
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2120574&HistoricalAwards=false
• 关键词: Tracking; Past; Ice; Sheets; North

This team of investigators will build a framework to test past ice sheet geometries using shifts in river drainage basin boundaries induced by glacial isostatic adjustment, as recorded by sediment provenance. They will simulate topographic change over North America using a state-of-the-art gravitationally self-consistent glacial isostatic adjustment model. They will perform calculations using two differing potential ice sheet loading histories over the last ice age. Using these predictions, they will calculate how drainage basin boundaries changed over the last ice age (120-0 ka) for major North American river systems. To model sediment provenance variations, they will superimpose a North American bedrock age map onto the predicted maps of drainage basin shifts due to glacial isostatic adjustment. Finally, they can predict how glacial isostatic adjustment shifts the age distribution of detrital grains (sediment provenance) drained into major North American Rivers over the ice age. Ultimately these predictions can be compared to existing and future sediment provenance records to identify likely past ice sheet size and geometry. This project will support an early-career principal investigator from an underrepresented group. She will develop innovative teaching tools for making legible the roots of geoscience culture in scientific racism and imperialism. These tools will be incorporated into courses taught at UC Santa Cruz. The project will support a PhD student and their enrollment in the Science & Justice Training Program. Here the student will learn how science is implicated in the co-production of social inequities. The principal investigator will participate in outreach to middle school students in the Alaska Native Science & Engineering Program and will mentor summer undergraduate students through the UC-HBCU Initiative.This interdisciplinary work, spanning geophysics, geomorphology, and sedimentology, will improve our understanding of past continental ice sheets and associated climate change. The research will expand the current toolset for inferring past ice sheets, setting a foundation for an unprecedented, novel method aimed at ice-sheet reconstruction over multiple glacial cycles. By robustly testing the influence of glacial isostatic adjustment on drainage basin shifts recorded in sediment provenance, the team will demonstrate the plausibility of drainage basin evolution as a potential new constraint on past ice sheets. This finding would enable ice-age researchers to transcend challenges imposed by the erosional nature of ice sheets, which destroy geologic evidence of past ice margins as they advance. Instead, it should be possible to infer the geographic extent and thickness of past ice sheets deeper in time, over many glacial cycles, and this approach is limited only by the age of sedimentary deposits, which can span millions of years. Furthermore, quantifying the influence of glacial isostatic adjustment on river drainage basins will improve our understanding of landscape evolution on ice age timescales.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.

该研究小组将建立一个框架，利用沉积物来源记录的冰川均衡调整引起的河流流域盆地边界的变化来测试过去的冰盖几何形状。他们将使用最先进的重力自洽冰川均衡调整模型来模拟北美的地形变化。他们将使用上一个冰河时期两个不同的潜在冰盖加载历史进行计算。利用这些预测，他们将计算北美主要河流系统在上一个冰河时代（120-0ka）期间流域边界如何变化。为了模拟沉积物来源变化，他们将北美基岩年龄图叠加到由于冰川均衡调整而导致流域盆地变化的预测图上。最后，他们可以预测冰川均衡调整如何改变冰河时期流入北美主要河流的碎屑颗粒（沉积物来源）的年龄分布。最终，这些预测可以与现有和未来的沉积物来源记录进行比较，以确定过去可能的冰盖尺寸和几何形状。该项目将支持来自代表性不足群体的早期职业首席研究员。她将开发创新的教学工具，使地球科学文化的根源在科学种族主义和帝国主义中清晰可见。这些工具将被纳入加州大学圣克鲁斯分校教授的课程中。该项目将支持一名博士生及其参加科学与正义培训计划。在这里，学生将了解科学如何与社会不平等的共同生产有关。首席研究员将参与阿拉斯加本土科学与工程计划中的中学生外展活动，并将通过 UC-HBCU 计划指导暑期本科生。这项跨学科工作涵盖地球物理学、地貌学和沉积学，将增进我们对过去的了解大陆冰盖和相关的气候变化。该研究将扩展当前用于推断过去冰盖的工具集，为旨在重建多个冰川周期冰盖的前所未有的新颖方法奠定基础。通过强有力地测试冰川均衡调整对沉积物来源中记录的流域盆地变化的影响，该团队将证明流域演化作为过去冰盖的潜在新约束的合理性。这一发现将使冰河时代的研究人员能够克服冰盖侵蚀性质带来的挑战，冰盖侵蚀性质会随着冰盖的推进而破坏过去冰缘的地质证据。相反，应该可以在许多冰川周期中更深入地推断过去冰盖的地理范围和厚度，而这种方法仅受沉积物年龄的限制，沉积物的年龄可以跨越数百万年。此外，量化冰川均衡调整对河流流域的影响将提高我们对冰河时代时间尺度上景观演化的理解。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。