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

魁北克-拉布拉多北部的冰川湖及其对冰川消融晚期和全新世早期气候区间融水排放的贡献

• 批准号: RGPIN-2017-05431
• 负责人: Roy, Martin
• 金额: $ 2.33万
• 依托单位: Université du Québec à Montréal
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=711643
• 关键词: glacial; lakes; northern; Quebec; Labrador

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.

过去15,000至7，000年的气候变化通常与在上一个冰河时代腐烂的冰块边缘发生的大型冰川湖的排水有关。据信，这些大规模的融合水爆发扰乱了北大西洋循环，该循环在调节地球气候方面起着基本作用。由于越来越多的研究表明，由于越来越多的研究表明，格陵兰融化和其他北极冰川融化的淡水释放增加可能会导致海洋热热盐循环的放缓并引起重要的气候反馈，因此这些以前的气候危机事件现在被关注。 在魁北克北部和拉布拉多，最后一次退化导致形成了几个大型冰川湖，这些湖泊入侵了Ungava湾附近的主要河谷。这些冰镇湖水排入了拉布拉多海，在那里反复和持续的融化排放可能破坏了海面条件的稳定，并改变/抑制了海洋关键部门的深水形成。尽管这些冰川湖的排水可能构成现代过程的出色类似物，但通过不确定性对冰撤退模式的不确定性以及对这些湖泊的构型（融合水容量）的缺乏限制，可以避免这些融合水对海洋系统和气候的精确影响。此外，脱气的主要阶段的时机仍然受到限制。 该研究计划基于将基于现场的研究和新的分析方法整合到对中北部Ungava和Labrador的沉积物和地貌记录的研究中。主要目标是：（1）通过系统的映射和冰川化学分析的冰川沉积物和地面的地球化学分析来表征冰缘期间冰缘的动力学和演变； （2）通过映射和高度测量的海岸线测量值重建8个冰川湖的程度和深度； （3）使用GIS模型为湖融合湖量提供了现实的估计。海岸线和爆发洪水沉积物的宇宙基因核素年代将进一步限制湖泊发育和排水的年代学，这应该有助于将这些融水排放放置在北大西洋脱水框架内。 总的来说，该研究计划将通过提供有关冰流模式和冰盖动态的全面知识来提高古地理重建的准确性，这是基本和应用科学的关键要素。这些结果还将提高我们对过去气候扰动和改进边界条件的作用的理解，这些条件是古/预测气候模型至关重要的，以充分评估淡水投入对海洋循环和气候的影响。