Laurentide Ice Sheet Dynamics: Applying Cosmogenic Exposure Dating to Constrain Chronology and Glacial Style in the Eastern Canadian Arctic; A Collaborative Proposal

0138566戴维斯这是科罗拉多大学和本特利学院首席研究人员共同提出的建议。在过去的半个世纪里，人们对Laurentide冰盖(LIS)的认识已经从一个具有相对稳定的中心核心的厚重的整体穹顶发展到一个更薄、更多穹顶和更具内在不稳定性的动态系统。冰盖在气候系统中的作用包括随着其高度的增加对大气流动的扰动，以及由于反照率的变化而改变行星能量平衡。此外，通过大量的冰山和融水排放，冰盖是北大西洋热盐环流的决定因素，这是气候系统中最大的非线性。有关大陆冰川作用的时间和类型的主要信息在这一概念演变中发挥了关键作用。沿着LIS的东北边缘，广泛的冰川系列提供了过去冰盖行为的直接记录。早期的研究因无法直接确定这些存款的年代而受到限制。因此，提出了沿冰盖所有边缘的冰川推进的时间和大小相似的论点，以及前冰盖不同部分之间基本上不同步的反应。随着宇宙暴露测年技术的发展，现在可以直接测定冰雹的年龄，并解决这一争论的大部分问题。最近的研究确定了这种方法在克莱德的实用性，并为两种相互竞争但可验证的冰川历史假说提供了基础。假设1预测，在克莱德和阿斯顿角前缘保存的冰凌系统之一是最后一次冰期最大(LGM)边缘位置，在整个LGM期间，冰雹上方的高地和冰雹以外的沿海前陆保持在大陆冰的界限之外。隐含的是认识到更广泛的冰川发生在上一次冰川周期的早期。对于假设2，初步结果表明，另一种模型可能也是可信的：在末次冰期早期，该地区被非侵蚀性冰完全淹没，随后冰盖重组为类似于假设1所预测的形状。解决这两个假设可能是理解LIS在最后一次冰川中行为的最重要的一步。除了解决LGM冰缘和冰川风格外，首席调查员还将提供克莱德湾和伊努苏因湾冰川年代的详细年表。

0138566DavisThis is a collaborative proposal by Principal Investigators at the University of Colorado and Bentley College. Over the past half century, the perception of the Laurentide Ice Sheet (LIS) has developed from a thick monolithic dome with a relatively stable central core, to a thinner, multi-domed and more dynamic system with inherent instabilities. The role of the ice sheet in the climate system includes perturbations to atmospheric flow as its height increased and altering the planetary energy balance due to albedo changes. In addition, through massive ice-berg and meltwater discharges, the ice sheet was a determinant on North Atlantic thermo-haline circulation, the greatest non-linearity in the climate system. Primary information on the timing and style of continental glaciation has played a key role in this conceptual evolution. Along the northeastern margin of the LIS, extensive series of moraines provide a direct record of past ice-sheet behavior. Early studies were limited by an inability to date these deposits directly. Consequently, arguments were advanced for both a similar timing and magnitude of glacial advances along all margins of the ice sheet, and for fundamentally asynchronous responses between different sectors of the former ice sheet. With the development of cosmogenic exposure dating, it is now possible to date the moraines directly and resolve much of this debate. Recent studies establish the utility of the method at Clyde and provide the basis for two competing, but testable hypotheses of the glacial history. Hypothesis 1 predicts that one of the moraine systems preserved on the Clyde and Cape Aston forelands is the last glacial maximum (LGM) marginal position, and that highlands above the moraines and coastal forelands outside the moraines remained beyond the limit of continental ice throughout the LGM. Implicit is the recognition that more extensive glaciations occurred earlier in the last glacial cycle. For hypothesis 2, preliminary results suggest that an alternative model might also be plausible: complete inundation of the region by non-erosive ice early in the LGM followed by a reorganization of the ice sheet later to a configuration similar to that projected in Hypothesis 1. Resolving these two hypotheses is probably the single most important step to understand the behavior of the LIS through the last glaciation. In addition to resolving the LGM ice limits and glacial style, the Principal Investigators will produce a detailed chronology of dated moraines from Clyde and Inugsuin fiords.