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

本研究的目的是探讨海平面反馈（SLF）在稳定海洋冰盖退缩过程中的重要性。拟议的调查将结合从苏格兰西北部凸起的海岸线、现有的近海海洋岩心和隔离盆地收集的新的晚更新世/全新世相对海平面约束，以完善不列颠群岛的冰川均衡调整（GIA）模型。该提案还将在更局部的水平和曾经流经苏格兰西北部明奇的晚更新世冰流的规模上调查SLF反馈。具体来说，我们将测试三个假设：1)末次极大期后Minch冰流消退期间，SLF并没有提供稳定影响，2)沿着缩进的冰盖边缘，SLF不是由局部冰锋控制，而是由区域GIA信号控制，3)SLF对稳定海洋冰流的影响是其下方地球流变的函数。与未来海平面上升预测有关的最大不确定因素之一是冰盖的影响。根据现有冰盖在海平面持续上升和变暖方面的表现，模式对未来100年的预测差异可达2米。我们对现有冰流（如南极洲的Thwaites冰川，格陵兰岛的Jakobshavn Isbrae冰川）尺度上的冰盖行为和海平面变化之间的反馈的理解仅限于数值模型，这些模型很少在年代际到世纪的时间尺度上对现实世界的例子进行测试。末次盛冰期后冰流的退缩为研究冰流退缩过程中控制冰流行为的因素提供了一个很好的试验场。作为该项目的一部分产生的数据不仅将检查冰盖的行为，而且还有助于GIA模型用于预测未来的海平面变化和过去的气候，古地理和考古研究。它还将提供苏格兰西北部凸起海岸线的第一批绝对年龄。

The purpose of the proposed research is to investigate the importance of sea-level feedbacks (SLF) 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 (GIA) models for the British Isles. The proposal will also investigate SLF feedbacks at a more local level and at the scale of a Late Pleistocene ice stream that once flowed through the Minch of northwestern Scotland. Specifically, we will test three hypotheses: 1.) SLF 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, SLF are governed not by the local ice front but by the regional GIA signal, and 3.) the influence of SLF in stabilizing marine ice streams is a function of the rheology of the Earth beneath it.One of the largest uncertainties related to future projections of sea-level rise is the influence of ice sheets. Model projections differ by as much as 2 m over the next 100 years depending on how existing ice sheets behave with respect to ongoing sea-level rise and warming. Our understanding of the feedbacks between ice sheet behavior and sea-level changes at the scale of extant ice streams of concern (e.g. Thwaites Glacier in Antarctica, Jakobshavn Isbrae in Greenland) is limited to numerical models that have rarely been tested against real-world examples at decadal to century time-scales. The retreat of ice streams following the Last Glacial Maximum provides an excellent test ground for the factors controlling the behavior of ice streams during their retreat. The data generated as part of this project will not only examine ice-sheet behavior but also contribute to GIA models used to predict future sea-level changes and past studies of climate, paleogeography, and archeology. It will also provide some of the first absolute ages on raised shorelines across northwestern Scotland.