NSFGEO-NERC: Collaborative Research: How important are sea-level feedbacks in stabilizing marine-based ice streams?

NSFGEO-NERC：合作研究：海平面反馈对于稳定海洋冰流有多重要？

• 批准号: 2147752
• 负责人: Jeremy Bassis
• 金额: $ 20万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 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: 2022-09-01 至 2025-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2147752&HistoricalAwards=false
• 关键词: NSFGEO; NERC; Collaborative; Research; How

Among the largest uncertainties in projections of 21st century sea-level rise is whether and how the Greenland and Antarctic Ice Sheets may collapse as global temperatures increase. One aspect of this uncertainty concerns how the solid Earth responds to melting ice in the form of post-glacial rebound, that is, uplift of crust after the weight of the ice has been removed. This project will examine the behavior of the Earth beneath the ice sheet that covered northwest Scotland during the Last Glacial Maximum, 20,000 years ago. As the earth warmed following the Last Glacial Maximum the ice sheet shrank and around 17,000 years ago a portion of the ice sheet over northwest Scotland experienced a “collapse” or period of fast retreat. The research will use records of past sea levels to document the behavior of the Earth beneath the front of this retreating ice sheet to determine if it rebounded (uplifted) fast enough to help stabilize the retreating ice sheet. There will also be numerical experiments to recreate the behavior of the Earth and ice sheet during this time period and compare these model experiments with measured records of past sea level changes across Scotland. These comparisons will permit new insights into the behavior of retreating ice sheets and provide better constraints on the history and size of the ice sheet that once covered northwest Scotland. The project will conduct a three-week in-residence summer camp for students from high schools with large minority populations to introduce them to the varied dimensions of Earth Science. The purpose of this research is to investigate the importance of sea-level feedbacks in stabilizing marine-based ice sheets during their retreat. The proposed investigation will combine new late Pleistocene/Holocene relative sea-level constraints to be collected from raised shorelines, existing offshore marine cores, and isolation basins from across northwestern Scotland, to refine the glacial isostatic adjustment models for the British Isles. The proposal will also investigate sea-level feedbacks at a more local level and at the scale of the Late Pleistocene ice stream that once flowed through the Minch of northwestern Scotland using a more specialized ice-sheet model. This model, coupled with results from an improved “global” scale glacial isostatic adjustment model for the British Isles, will be used to understand the sensitivity of the former Minch ice stream to more local variables (e.g. mantle rheology, lithospheric thickness, ice sheet geometry, etc.). Three hypotheses will be tested: 1.) Sea-level feedback did not provide a stabilizing influence for the Minch Ice Stream during its retreat following the Last Glacial Maximum; 2.) along indented ice-sheet margins, sea-level feedbacks are governed not by the local ice front but by regional isostatic adjustment; and 3.) the influence of sea-level feedback in stabilizing marine ice streams is a function of the rheology of the Earth beneath it.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.

在预测21世纪世纪海平面上升的最大的不确定性之一是，随着全球气温的上升，格陵兰岛和南极冰盖是否会崩溃，以及如何崩溃。这种不确定性的一个方面涉及固体地球如何以冰后反弹的形式对融化的冰作出反应，即在冰的重量被移除后地壳的隆起。 该项目将研究20,000年前末次盛冰期覆盖苏格兰西北部的冰盖下的地球行为。 随着地球在末次盛冰期后变暖，冰盖缩小，大约17,000年前，苏格兰西北部的一部分冰盖经历了“崩溃”或快速退缩的时期。 该研究将使用过去海平面的记录来记录地球在这一退缩的冰盖前部下方的行为，以确定它是否反弹（上升）得足够快，以帮助稳定退缩的冰盖。还将进行数值实验，以重现地球和冰盖在这段时间内的行为，并将这些模型实验与苏格兰过去海平面变化的测量记录进行比较。 这些比较将使人们对冰盖退缩的行为有新的认识，并对曾经覆盖苏格兰西北部的冰盖的历史和大小提供更好的限制。 该项目将为来自少数民族人口众多的高中的学生举办为期三周的住校夏令营，向他们介绍地球科学的各个方面。 本研究的目的是调查海平面反馈在稳定海基冰盖在其撤退期间的重要性。 拟议的调查将结合联合收割机新的晚更新世/全新世相对海平面的限制，从苏格兰西北部的海岸线，现有的海上海洋岩心和隔离盆地收集，以完善不列颠群岛的冰川均衡调整模型。 该提案还将调查海平面反馈，在更地方的水平和规模的晚更新世冰流，曾经流过苏格兰西北部的明奇使用一个更专业的冰盖模型。 这个模型，再加上一个改进的“全球”规模的冰川均衡调整模型的不列颠群岛的结果，将被用来了解前明奇冰流的敏感性，更多的本地变量（如地幔流变学，岩石圈厚度，冰盖几何形状等）。将测试三个假设：1）。在末次盛冰期之后的撤退期间，海平面反馈并没有为明奇冰流提供稳定的影响; 2）沿着锯齿状冰盖边缘，海平面反馈不是由当地的冰锋，而是由区域均衡调整;和3）。海平面反馈在稳定海洋冰流方面的影响是其下方地球流变学的函数。2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。