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

这是一项由科罗拉多大学和宾利学院的主要研究人员合作提出的建议。在过去的半个世纪里，人们对劳伦泰德冰盖（LIS）的认识已经从一个具有相对稳定的中心核心的厚单圆顶发展到一个更薄、多圆顶和更动态的系统，具有固有的不稳定性。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的排放，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。关于大陆冰川作用的时间和类型的初步资料在这一概念演变中起了关键作用。沿着美国的东北边缘，广泛的一系列冰碛提供了过去冰盖行为的直接记录。由于无法直接确定这些沉积物的年代，早期的研究受到了限制。因此，人们提出的论点是，沿冰盖所有边缘的冰川推进的时间和幅度相似，并且在原冰盖的不同部分之间基本上是不同步的响应。随着宇宙成因暴露年代测定法的发展，现在可以直接测定冰碛的年代，并解决了许多争论。最近的研究证实了该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史假设提供了基础。假设1预测，保存在克莱德和阿斯顿角前塬上的一个冰碛系统是末次冰盛期（LGM）的边缘位置，在末次冰盛期，冰碛之上的高地和冰碛之外的沿海前塬在整个冰盛期都没有大陆冰的覆盖。隐含的认识是，更广泛的冰期发生在末次冰期旋回的早期。对于假设2，初步结果表明，另一种模式也可能是合理的：在大冰期早期，该地区被非侵蚀性冰完全淹没，随后冰盖重组，形成类似于假设1所预测的结构。解决这两个假设可能是理解末次冰期冰川行为的最重要的一步。除了解决LGM的冰限和冰川类型之外，首席调查员还将制作克莱德和Inugsuin峡湾冰碛的详细年表。

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.