Development of a glacial abrasion rule for landscape-evolution models

冰川景观是由在其上滑动的冰雕刻而成的。 冰的不断流动磨损了下面的基岩，随着时间的推移侵蚀了它。 这种磨损的速率和模式部分源于一种称为磨蚀的过程，该过程是由基冰中携带的沉积物被压入底层岩石并被冰川沿着推移而产生的。 已经提出了许多理论来估计磨损率，这取决于众多的参数。为了准确地模拟冰川景观的演变，需要一个数学的“磨蚀定律”，准确地捕捉到与磨蚀相关的物理现象。 在真实的冰川下，磨蚀规律的形式很难确定，因为冰川床常常难以接近，而且控制因素很难在野外测量。 进一步加剧这些困难的是，磨损率是微不足道的，因此需要几十年或几个世纪的时间才能测量侵蚀量。该项目的目标是开发一种数学关系，使用一套新的实验室仪器来描述冰川磨损的物理学，以便可以在数字景观演变模型中实现。在实验室中，可以控制和测量条件，精确确定磨损规律所需的精度。该项目将支持一个研究生和本科生从威斯康星大学麦迪逊分校，并提供来自梅诺米尼Nation.A大直径环剪切装置和直接剪切装置的大学代表性不足的学生培训将被用于滑动碎片装载冰在压力熔点在不同的形状和组成的岩石床。将使用白色光干涉仪分析磨损产生的条纹，该干涉仪能够测量低至10-18立方米的侵蚀材料体积。由于能够测量这些微小的体积，滑动实验可以在相对较短的时间内进行（每次不到一个月），并且仍然产生足够的磨损体积来确定磨损规律。使用这些仪器，将制定一个磨损规律，将侵蚀速率与独立变量联系起来，如滑动速度、基底熔化、河床形状、碎屑硬度和碎屑浓度。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。

Glacial landscapes are sculpted by the ice that slides above them. The constant flow of ice wears away at the underlying bedrock, eroding it through time. The rates and patterns of this wear stem in part from a process called abrasion, which results from sediment entrained in basal ice being pressed into the underlying rock and drug along by the glacier. A number of theories have been proposed to estimate abrasion rates, which depend on a multitude of parameters. In order to accurately model the evolution of glacial landscapes, a mathematical “abrasion law” is needed that accurately captures the physics relevant to abrasion. The form of the abrasion law is difficult to determine beneath real glaciers because their beds are often inaccessible and the controlling factors are difficult to measure in the field. Further compounding these difficulties is the fact that abrasion rates are miniscule and therefore require decades or centuries to pass before the eroded volume is measurable. The goal of this project is to develop a mathematical relationship that describes the physics of glacial abrasion using a novel set of laboratory instruments, so that it can be implemented in numerical landscape evolution models. In the laboratory, conditions can be controlled and measured with the precision needed to accurately determine the abrasion law. The project will support a graduate and an undergraduate student from UW-Madison and provide training for underrepresented students from the College of Menominee Nation.A large-diameter ring shear device and a direct shear device at UW-Madison will be used to slide debris-laden ice at the pressure melting point over rock beds that vary in shape and composition. The striations produced by abrasion will be analyzed using a white light interferometer capable of measuring the volume of eroded material down to 10-18 cubic meters. With the ability to measure these miniscule volumes, the sliding experiments can be conducted in relatively short timeframes (less than one month each) and still generate sufficient abraded volume to determine the abrasion law. Using these instruments, an abrasion law will be developed that relates the rate of erosion to independent variables, such as sliding speed, basal melting, bed shape, debris hardness, and debris concentration.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.