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

这个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模拟北美的地形变化。他们将使用上一个冰河时代两个不同的潜在冰盖载荷历史进行计算。利用这些预测，他们将计算北美主要河流系统在最后一个冰河时代（120-0 ka）的流域边界如何变化。为了模拟沉积物来源的变化，他们将把北美基岩年龄图绘制到由于冰川均衡调整而引起的流域变化的预测图上。最后，他们可以预测冰川均衡调整如何改变冰河时期排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大小和几何形状。该项目将支持一个代表性不足的群体的早期职业生涯的首席研究员。她将开发创新的教学工具，使地球科学文化在科学种族主义和帝国主义的根源清晰可辨。这些工具将被纳入在加州大学圣克鲁斯教授的课程。该项目将支持一名博士生及其在科学正义培训计划中的入学。在这里，学生将学习如何科学是牵连在社会不平等的共同生产。首席研究员将参与阿拉斯加土著科学工程项目的中学生外展活动，并将通过UC-HBCU倡议指导暑期本科生。这项跨学科的工作，跨越地球物理学，地貌学和沉积学，将提高我们对过去大陆冰盖和相关气候变化的理解。这项研究将扩大目前推断过去冰盖的工具集，为一种前所未有的新方法奠定基础，该方法旨在重建多个冰川周期的冰盖。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变化的影响，该团队将证明流域演变的可解释性，作为对过去冰盖的潜在新约束。这一发现将使冰河时代的研究人员能够超越冰盖侵蚀性质所带来的挑战，冰盖侵蚀性质在前进过程中破坏了过去冰缘的地质证据。相反，应该可以推断出过去冰盖的地理范围和厚度，在许多冰川循环中，这种方法只受到沉积物年龄的限制，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变的理解。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.