Late Quaternary Dynamics of the Labrador/Foxe Sectors of the Laurentide Ice Sheet, Eastern Caradian Artic

在过去的五年中，我们对Laurentide冰原（LIS）稳定性及其在全球气候系统中的作用的概念已经发生了巨大的变化，因为从海底、冰芯和原冰原边缘沉积物中收集了高分辨率的记录。总的来说，这些记录在几年到几十年的时间尺度上记录了海洋和大气环流的快速重组，在几十年到几百年的时间尺度上记录了冰缘的快速波动，导致大量冰向海洋转移。大量冰从陆地向海洋的快速输送可能改变了温盐环流，随后高纬度降水减少，有效地将这三个系统耦合在一起。过去十年，INSTAAR的研究工作主要集中在哈德逊海峡河口的冰川历史上，那里是冰盖与海洋最直接的联系。我们已经提供了哈德逊海峡冰缘快速前进和后退的实地证据（持续前进超过100公里/世纪），以及独立于地形的冰运动，主要进展来自拉布拉多/恩加瓦，而不是哈德逊湾。这些进展的一个结果是冰山大量流入拉布拉多海，随后流入北大西洋，为在北大西洋观察到的海因里希层形成机制提供了第一个直接的冰川地质证据。在本提案中，资金被要求测试三个问题：1)观测到的快速冰流推进是由美国大陆床上固有的不稳定性引发的，还是由气候驱动的？坎伯兰海峡的冰流是否向拉布拉多海贡献了大量的沉积物/融水/冰山？如果是这样，波动是否与哈德逊海峡的推进相一致？3)根据野外证据解释的重建结果是否符合冰川学理论？我们建议通过对坎伯兰峡口冰川地质的实地观察，并利用我们基于实地的边界条件，将一个3-D冰川学模型应用于拉布拉多/巴芬地区，来解决这些问题。坎伯兰湾地区应该保留证据，以澄清福克斯盆地冰流的时间和规模，并在北部提供当地冰川活动的独立记录。将这些冰块前进的时间与哈德逊海峡的时间进行比较，将表明强迫主要是气候还是冰盖不稳定。模拟我们的实地冰川重建将测试它们是否与冰物理兼容，并为冰盖动力学提供额外的见解。

9510063 Miller Our concepts concerning the stability of the Laurentide Ice Sheet (LIS) and its role in the global climate systems have been revised dramatically in the past five years, as high-resolution records have been compiled from the sea floor, ice cores, and from deposits around the margin of the former ice sheet. Collectively, these records document rapid reorganization of oceanic and atmospheric circulation on time scales of a few years to a few decades, and rapid fluctuations of the ice margin that resulted in massive transfers of ice into oceans on time scales of decades to centuries. The rapid delivery of large volumes of ice from the land to the ocean may have altered thermohaline circulation with subsequent reduction in high-latitude precipitation, effectively coupling the three systems. The INSTAAR research effort of the last decade has focused on the glacial history at the mouth of Hudson Strait, the most direct connection of the ice sheet to the ocean. We have provided field evidence for rapid advance and retreat of the ice margin in Hudson Strait (sustained advances in excess of 100 km/century), and for ice movement independent of topography, with major advances sourced in Labrador/Ungava rather than Hudson Bay. A consequence of these advances was a major flux of icebergs into the Labrador Sea and subsequently the North Atlantic, providing the first direct glacial geologic evidence of a mechanism to produce Heinrich layers observed in the North Atlantic. In this proposal funding is requested to test three questions: 1) Are observed rapid icestream advances triggered by inherent instabilities at the bed of the LIS, or are they climatically driven? 2) Did an ice stream in Cumberland Sound contribute substantial sediment/meltwater/icebergs to the Labrador Sea. If so, were fluctuations in phase with the Hudson Strait advances? and 3) Are the reconstructions interpreted from the field evidence compatible with glaciological theory? We proposed to address these questions by field observations of the glacial geology at the mouth of Cumberland Sound and by applying a 3-D glaciological model to the Labrador/Baffin region using our field-based boundary conditions. The Cumberland Sound region should preserve evidence that will clarify the timing and magnitude of a Foxe Basin ice stream, and to the north, provide an independent record of local glacier activity. Comparing the timing of advances for these ice masses with that in Hudson Strait will indicate whether forcing is primarily climate or ice sheet instability. Modeling our field-base glacier reconstructions will test whether they are compatible with ice physics and provide additional insights into ice sheet dynamics.