The influence of fast-draining subglacial lakes on the hydrology and dynamics of the Greenland Ice Sheet

冰下水文学是控制格陵兰冰盖质量损失的关键因素，因为它对消融区的冰运动和海洋终止冰川的正面消融产生了影响。冰下湖泊是这一冰下水文系统的关键组成部分。堆积在湖床上的沉积物可能是过去冰盖结构、古环境和古气候变化以及生命存在的潜在档案。冰下湖水为微生物群落提供了栖息地，也为其他行星上的生命提供了类似物。大量水的局部储存和下游排水调节了基础水文和生物地球化学循环/过程，并可能引发冰缘的崩解和短暂(数周至数月)和长期的冰流变化。排水还可以形成渠道，切割成冰或进入河床，并将大量水和泥沙输送到下游。最后，发生在冰川前陆的洪水对下游的生命和基础设施构成了重大威胁。尽管有充分的记录表明，南极冰盖下有数百个冰下湖泊，但在格陵兰岛，冰下湖泊直到最近才得到很少的关注，因为冰盖的几何形状导致人们认为它们是稀有的。然而，我们团队成员最近的工作表明，格陵兰冰盖下的湖泊分布广泛，而且与南极洲不同，湖泊可以是高度动态的特征，由冰面融化提供营养，并可以在几周内迅速排干。因此，它们是格陵兰和南极洲冰下湖泊在更温暖的世界中如何表现的重要终端成员，因为表面融化变得更加普遍，进入更广泛的河床，湖泊排水变得更加活跃。然而，控制冰下湖泊形成和动态的关键过程及其对格陵兰基础水文和冰流的影响尚未确定。因此，需要将详细的实地数据与数值模拟结合起来，以准确确定这些环境的性质，并评估它们对冰盖、冰下水文学和冰动力学的影响。该项目将组建一个世界领先的多学科团队，对格陵兰多个快速排水的冰下湖泊进行首次实地表征和监测，用于约束和测试最先进的冰下水文模型。它得益于确认在Isunnguata Seria下发现了三个快速排水的冰下湖泊，这是地球上最容易进入的湖泊，因此提供了一个以后勤经济和低风险进行高回报发现科学的机会。其目的是量化快速排水的冰下湖泊对格陵兰冰盖的水文学和动力学的作用，以：(I)提高我们对冰下湖泊在调节格陵兰冰下水文和动态方面的作用的了解；(Ii)了解它们未来对格陵兰和南极洲的影响，(Iii)生成数据，使冰盖和水文模型专家能够改进他们对全球海平面指数未来对海平面上升贡献的预测，(Iv)为格陵兰今后的冰下湖泊勘探奠定科学基础，以便研究过去的冰和气候变化，探索冰下生物和生物地球化学通量。

Subglacial hydrology is a critical control on mass loss from the Greenland Ice Sheet via its impact on ice motion in the ablation zone and frontal ablation of marine terminating glaciers. Subglacial lakes are a key component of this subglacial hydrological system. Sediments that accumulate on lake beds are potential archives of past ice sheet configurations, paleoenvironmental and palaeoclimate change, and the presence of life. Subglacial lake water provides a habitat for microbial communities and an analogue for life on other planetary bodies. The localised storage and downstream drainage of large volumes of water modulates basal hydrology and biogeochemical cycles/processes, and can trigger calving at the ice margin and transient (weeks to months) and long-term ice-flow variations. Drainage events can also form channels, cut up into the ice or down into the bed, and transport large volumes of water and sediment downstream. Finally, outburst floods onto the glacier foreland present a major hazard to downstream life and infrastructure. Although it is well documented that hundreds of subglacial lakes exist beneath the Antarctic Ice Sheet, in Greenland, subglacial lakes have until recently received little attention because the geometry of the ice sheet led to the assumption that they were scarce. However, recent work from members of our team demonstrate that lakes are widespread beneath the Greenland Ice Sheet and moreover, can be highly dynamic features that, in contrast to Antarctica, are fed by melt from the ice surface and can drain rapidly in a matter of weeks. They therefore represent an important end-member for how subglacial lakes in both Greenland and Antarctica will behave in a warmer world as surface melting becomes more prevalent, accesses a wider portion of the bed, and lake drainage becomes more vigorous. Yet the key processes controlling subglacial lake formation and dynamics, and their impact on basal hydrology and ice flow in Greenland have yet to be identified. What is needed therefore is detailed field data integrated with numerical modelling to accurately determine the properties of these environments and assess their influence on ice sheet subglacial hydrology and ice dynamics. The project will assemble a world-leading multidisciplinary team to undertake the first field-based characterisation and monitoring of multiple fast-draining subglacial lakes in Greenland, which will be used to constrain and test a state-of-the-art subglacial hydrological model. It benefits from the confirmed discovery of three fast-draining subglacial lakes beneath Isunnguata Sermia, which are the most accessible on the planet and therefore provide an opportunity to conduct high-reward discovery science with logistical economy and low risk. The aim is to quantify the role of fast-draining subglacial lakes on the hydrology and dynamics of the Greenland Ice Sheet to: (i) improve our understanding of the role of subglacial lakes in modulating subglacial hydrology and dynamics in Greenland; (ii) provide insight into their future impact in both Greenland and Antarctica, (iii) generate data to enable ice sheet and hydrological modellers to improve their predictions of the future contribution of the GrIS to sea level rise, and (iv) develop the scientific basis for future subglacial lake exploration in Greenland for investigating past ice and climate change and exploring subglacial biology and biogeochemical fluxes.