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

这是科罗拉多大学和本特利学院的主要研究人员的合作提案。 在过去的半个世纪里，劳伦泰德冰盖（LIS）的概念已经从一个厚的单一圆顶与一个相对稳定的中央核心，发展成为一个薄，多圆顶和更动态的系统与固有的不稳定性。冰盖在气候系统中的作用包括随着其高度的增加而对大气流动的扰动，以及由于温度变化而改变行星的能量平衡。此外，通过大规模的冰山和融水排放，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。关于大陆冰川作用时间和类型的原始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，大量的冰碛提供了过去冰盖行为的直接记录。 早期的研究由于无法直接确定这些沉积物的年代而受到限制。因此，人们提出了这样的论点：沿着冰盖的所有边缘，冰川前进的时间和幅度都相似，而且前冰盖的不同部分之间的反应从根本上是异步的。沿着冰盖的所有边缘。随着宇宙成因暴露年代测定的发展，现在可以直接测定冰碛的年代，并解决这一争论。 最近的研究确立了该方法在克莱德的实用性，并为两个相互竞争但可检验的冰川历史假说提供了基础。 假设1预测，保存在克莱德和阿斯顿角前陆的冰碛系统之一是末次盛冰期（LGM）的边缘位置，冰碛上方的高地和冰碛外的沿海前陆在整个LGM期间仍然超出大陆冰的界限。隐含的是认识到更广泛的冰川发生在最后一个冰川周期的早期。对于假设2，初步结果表明，另一种模型也可能是合理的：在LGM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中预测的配置。解决这两个假设可能是理解末次冰期LIS行为的最重要的一步。除了解决末次冰期的冰限和冰川风格，主要调查人员将产生一个详细的年代表的日期冰碛从克莱德和Inugsuin峡湾。

OPP-0138586MillerThis 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.