The glacial lakes of northern Quebec-Labrador and their contribution to the meltwater discharges of the late deglaciation and early Holocene climate interval

过去15000年至7000年的气候变化通常与大型冰川湖的排水有关，这些冰川湖是在最后一个冰河时代的腐烂冰块边缘形成的。据信，这些大规模的融水爆发扰乱了北大西洋环流，而北大西洋环流在调节地球气候方面起着重要作用。这些以前的气候强迫事件现在受到关注，因为越来越多的研究表明，目前格陵兰岛和其他北极冰川融化所释放的淡水增加，可能会导致海洋温盐环流减缓，并引起重要的气候反馈。***在魁北克省北部和拉布拉多，最后一次冰川消退导致了几个大型冰川湖的形成，这些冰川湖侵入了昂加瓦湾周围的主要河谷。这些冰坝湖泊流入拉布拉多海，在那里，反复持续的融水排放可能破坏了海洋表面条件的稳定，并改变/抑制了海洋这一关键区域的深水地层形成。虽然这些冰川湖的排水可能形成现代过程的杰出模拟，但由于冰退缩模式的不确定性和对这些湖泊的配置（融水体积）缺乏限制，无法评估这些融水排放对海洋系统和气候的精确影响。此外，对消冰主要阶段的时间仍然知之甚少。***本研究计划是基于实地调查和新分析方法对恩加瓦和拉布拉多中北部沉积物和地貌记录的综合研究。研究的主要目标是：(1)通过对冰川沉积物和地貌的系统制图和地球化学分析，表征冰缘在消冰过程中的动力学和演化特征；(2)通过填图和高程测量重建了8个冰湖的范围和深度；(3)利用GIS模型提供湖泊融水容量的现实估计。海岸线和溃决洪水沉积物的宇宙成因核素定年将进一步限制湖泊发育和排水的年代学，这将有助于将这些融水排放置于北大西洋消冰框架内。***总的来说，该研究项目将通过提供冰流模式和冰盖动力学的全面知识来提高古地理重建的准确性，这是基础科学和应用科学的关键要素。这些结果还将提高我们对融水排放在过去气候扰动中的作用的理解，并完善古/预测气候模型所迫切需要的边界条件，以充分评估淡水输入对海洋环流和气候的影响。

The climate variability of the last 15,000 to 7,000 years is commonly linked to the drainage of large glacial lakes that had developed at the margins of the decaying ice masses of the last Ice Age. These massive outbursts of meltwater are believed to have disturbed the North Atlantic Ocean circulation, which plays a fundamental role in regulating Earth's climate. These former climate-forcing events are now under focus due to a growing number of studies showing that the present-day increase in freshwater releases from the melting of Greenland and other Arctic glaciers may potentially lead to a slowdown of the ocean thermohaline circulation and cause important climate feedbacks.*** In northern Quebec and Labrador, the last deglaciation led to the formation of several large glacial lakes that invaded the main river valleys around Ungava Bay. These ice-dammed lakes drained into the Labrador Sea where the repeated and sustained meltwater discharges likely destabilized the ocean surface conditions and altered/suppressed deepwater formation taking place in this key sector of the ocean. Although the drainage of these glacial lakes may form an outstanding analogue for modern processes, assessing the precise impact of these meltwater discharges on the ocean system and climate is prevented by uncertainties on the pattern of ice retreat and the lack of constraints on the configuration (meltwater volumes) of these lakes. Furthermore, the timing of the main stages of the deglaciation remains poorly constrained. *** This research program is based on the integration of field-based investigations and novel analytical methods to the study of the sediment and geomorphic records of north-central Ungava and Labrador. The main objectives are to: (1) characterize the dynamics and evolution of the ice margin during the deglaciation through systematic mapping and geochemical analyses of glacial sediments and landforms; (2) reconstruct the extent and depth of 8 glacial lakes though mapping and elevation measurements of raised shorelines; and (3) provide realistic estimates for the lake meltwater volumes using GIS models. Cosmogenic nuclide dating of shorelines and outburst flood deposits will further constrain the chronology of the lake development and drainage, which should contribute to place these meltwater discharges within the North Atlantic deglaciation framework.*** Altogether, this research program will improve the accuracy of paleogeographic reconstructions by providing a comprehensive knowledge of ice-flow patterns and ice sheet dynamics, which are critical elements in both fundamental and applied sciences. These results will also improve our understanding of the role of meltwater discharges in past climate perturbations and refine boundary conditions that are critically required by paleo/predictive climate models to fully assess the impact of freshwater inputs on ocean circulation and climate.