Variability in Laurentide ice sheet dynamics and global climate changes: a perspective fro mthe depositional record of the greater Hudson Bay region

哈德逊-詹姆斯湾的地理位置靠近劳伦泰德冰盖（LIS）的前地理中心，这使得该地区对冰盖动力学的研究尤为重要。大量的古气候代用物表明，大哈德逊湾地区是上一个冰期循环期间重要气候变化的起源，特别是由于北大西洋的冰山从海洋冰盖边缘断断续续地大量流出。这些所谓的海因里希事件在冰盖动力学方面意义重大，因为目前的冰川学模型将海因里希事件归因于哈德逊湾中心的一个大冰丘的突然崩塌。然而，基于现场的地质数据支持LIS的多圆顶结构。从多面和条纹岩石露头记录的移动冰流序列表明，这些冰穹的重要迁移可能与美国某些地区的海因里希型收缩事件有关。然而，这些冰流转移的时间，以及与冰架解体相关的确切冰流路径都没有得到充分的限制。因此，目前的数值模型与现有的地质观测结果不一致。本研究计划通过研究哈德逊-詹姆斯湾低地第四纪地貌和地层记录的各个方面来解决这些问题。该地区毗邻位于哈德逊湾东部和西部的美国最重要的两个冰穹的前移位区。因此，这些沉积序列应该对冰盖结构的变化敏感，并记录有关假定崩塌的信息。几个与非冰川沉积物互层的冰川单元的存在为整理冰运动的年代学提供了一个绝佳的机会。对非冰川沉积物定年将为冰流的移动顺序提供时间限制。该研究计划的一个长期目标是将LIS的演变和重组事件与深海沉积物记录的全球气候变化（如海因里希事件）联系起来。

The location of Hudson-James Bay near the former geographic center of the Laurentide ice sheet (LIS) makes this region particularly important for the study of ice sheet dynamics. Numerous paleoclimate proxies have shown that the greater Hudson Bay region was at the origin of important climate changes during the last glacial cycle, notably through episodic and massive discharges of icebergs in the North Atlantic Ocean from the margin of a marine-based ice sheet. These so-called Heinrich events are significant in term of ice sheet dynamics because current glaciological model attribute Heinrich events to an abrupt collapse of a large ice dome centered over Hudson Bay. Field-based geological data, however, argue for a multi-dome configuration of the LIS. Sequences of shifting ice flow documented from multi-faceted and striated rock outcrops indicate important migrations of these ice domes that could be related to Heinrich-type drawdown episodes of certain sectors of the LIS. However, the timing of these ice flow shifts, as well as the exact ice flow paths associated with the disintegration of the LIS are inadequately constrained. As a result, numerical models currently disagree with available geological observations. This research program addresses these issues by studying various aspects of the Quaternary geomorphic and stratigraphic records of the Hudson-James Bay lowlands. This region is adjacent to the former zones of displacement of two of the most important ice domes of the LIS, located east and west of Hudson Bay. These sedimentary sequences should thus be sensitive to changes in ice sheet configuration and record information on the postulated collapse. The presence of several glacial units interbedded with nonglacial sediments offers an outstanding opportunity to sort out the chronology of ice movements. Dating of the nonglacial deposits will provide chronological constraints on the shifting sequences of ice flow. A long-term objective of the research program is to correlate the evolution and episodes of reorganizations of the LIS with global climate changes (e.g. Heinrich events) documented from deep-sea sediment records.