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

9510063米勒我们关于劳伦蒂冰盖稳定性及其在全球气候系统中的作用的概念在过去五年中得到了极大的修订，因为从海底、冰芯和前冰盖边缘周围的沉积物汇编了高分辨率的记录。总的来说，这些记录记录了海洋和大气环流在几年到几十年的时间尺度上的迅速重组，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进入海洋。从陆地到海洋的大量冰的快速输送可能改变了温盐循环，从而减少了高纬度降水，有效地耦合了这三个系统。INSTAAR在过去十年的研究重点是哈德逊海峡入海口的冰川历史，哈德逊海峡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进退(持续进退超过100公里/世纪)的现场证据，并提供了不受地形影响的冰运动的现场证据，主要的进动来自拉布拉多/昂加瓦而不是哈德逊湾。这些进展的一个结果是大量冰山流入拉布拉多海，随后进入北大西洋，提供了第一个直接的冰川地质证据，证明了在北大西洋观察到的海因里奇层的形成机制。在这项提案中，要求提供资金来测试三个问题：1)观测到的冰川快速推进是由LIS海床固有的不稳定引发的，还是气候驱动的？2)坎伯兰海湾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推进同步？3)根据现场证据解释的重建结果是否与冰川学理论相符？我们建议通过对坎伯兰海湾入海口的冰川地质进行实地观察，并使用基于现场的边界条件将三维冰川学模型应用于拉布拉多/巴芬地区，来解决这些问题。坎伯兰海湾地区应该保存证据，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。将这些冰块的推进时间与哈德逊海峡的时间进行比较，将表明作用力主要是气候还是冰盖不稳定。我们的野外冰川重建模型将测试它们是否与冰物理兼容，并提供对冰盖动力学的更多见解。

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.