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

拟议研究的目的是调查海平面反馈(SLF)在海洋冰盖退缩过程中稳定的重要性。拟议的调查将结合新的晚更新世/全新世相对海平面限制条件，从升高的海岸线、现有的近海岩芯和苏格兰西北部的孤立盆地收集，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层面上调查SLF反馈，并在曾流经苏格兰西北部明奇的晚更新世冰流的规模上进行调查。具体地说，我们将检验三个假设：1)在最后一次冰川盛期之后的消退过程中，SLF没有为Minch冰流提供稳定的影响，2)沿着凹陷的冰盖边缘，SLF不是由当地的冰锋决定的，而是由区域GIA信号决定的。SLF在稳定海洋冰流方面的影响是其下方地球流变性的函数。与未来海平面上升预测有关的最大不确定性之一是冰盖的影响。根据现有冰盖在海平面持续上升和变暖方面的表现，模型预测在未来100年内的差异高达2米。我们对冰盖行为和海平面变化之间在现有冰流规模(例如南极洲的Thwaites冰川，格陵兰的Jakobshavn Isbrae)之间的反馈的理解仅限于数值模型，这些模型很少在十年到世纪的时间尺度上与真实世界的例子进行测试。末次冰川盛期之后冰流的退缩为控制冰流退缩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行为，还将有助于GIA模型用于预测未来的海平面变化，以及过去对气候、古地理和考古学的研究。它还将在苏格兰西北部的凸起海岸线上提供一些第一个绝对年龄。

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.