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

9510063 米勒 在过去的五年里，我们关于劳伦泰德冰盖（LIS）的稳定性及其在全球气候系统中的作用的概念已经被极大地修改，因为高分辨率记录已经从海底，冰芯和前冰盖边缘周围的沉积物中编译出来。 总的来说，这些记录了海洋和大气环流在几年到几十年的时间尺度上的快速重组，以及冰缘的快速波动，导致冰在几十年到几个世纪的时间尺度上大量转移到海洋中。 大量的冰从陆地迅速输送到海洋，可能改变了温盐环流，从而减少了高纬度降水，有效地耦合了三个系统。 在过去十年里，INSTAAR的研究工作集中在哈德逊海峡口的冰川历史上，这是冰盖与海洋最直接的连接。 我们提供了现场证据，证明哈德逊海峡冰缘的快速推进和后退（持续推进超过100 km/世纪），并证明冰的运动与地形无关，主要进展来源于拉布拉多/昂加瓦而不是哈德逊湾。 这些进步的结果是大量冰山流入拉布拉多海，随后流入北大西洋，为在北大西洋观察到的海因里希层的产生机制提供了第一个直接的冰川地质证据。 在这项提案中，要求提供资金来测试三个问题：1）观察到的快速冰沉积是由LIS底部的固有不稳定性引发的，还是由气候驱动的？2)坎伯兰海峡的冰流是否为拉布拉多海贡献了大量的沉积物/融水/冰山。 如果是这样的话，波动是否与哈德逊海峡的进展同步？（3）根据野外证据解释的重建结果是否与冰川学理论相一致？ 我们提出了解决这些问题的冰川地质在口的坎伯兰声音和应用3-D冰川模型拉布拉多/巴芬地区使用我们的实地边界条件的实地观察。 坎伯兰海峡地区应该保存证据，澄清福克斯盆地冰流的时间和规模，并向北，提供当地冰川活动的独立记录。 比较这些冰块与哈德逊海峡冰块的推进时间，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学兼容，并提供对冰盖动态的更多见解。

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.