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

冰下水文是控制格陵兰冰盖质量损失的关键因素，它通过影响消融带的冰运动和海洋终止冰川的锋面消融。冰下湖泊是冰下水文系统的重要组成部分。沉积在湖床上的沉积物是过去冰盖结构、古环境和古气候变化以及生命存在的潜在档案。冰川下的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的栖息地。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，并可能引发冰缘的产犊，以及短暂的（数周至数月）和长期的冰流变化。排水事件也可以形成通道，切割成冰或进入河床，并向下游输送大量的水和沉积物。最后，冰川前陆的溃决洪水对下游的生活和基础设施构成了重大威胁。尽管有充分的文献证明南极冰盖下存在着数百个冰下湖泊，但在格陵兰岛，冰下湖泊直到最近才受到很少的关注，因为冰盖的几何形状导致人们认为它们很稀少。然而，我们小组成员最近的工作表明，在格陵兰冰盖下，湖泊分布广泛，而且，与南极洲相比，湖泊可能是高度动态的特征，由冰表面的融化提供水源，并在几周内迅速流失。因此，它们代表了格陵兰岛和南极洲的冰下湖泊在一个更温暖的世界中如何表现的重要末端成员，因为表面融化变得更加普遍，进入更广泛的河床部分，湖泊排水变得更加有力。然而，控制冰下湖形成和动态的关键过程及其对格陵兰岛基础水文和冰流的影响尚未确定。因此，需要详细的实地数据与数值模拟相结合，以准确确定这些环境的性质，并评估它们对冰盖冰下水文和冰动力学的影响。该项目将组建一支世界领先的多学科团队，对格陵兰岛多个快速排水的冰下湖泊进行首次实地表征和监测，这将用于约束和测试最先进的冰下水文模型。它受益于在isunguata Sermia地下发现了三个快速排水的冰下湖泊，这是地球上最容易到达的，因此提供了一个以物流经济和低风险进行高回报发现科学的机会。目的是量化快速排水的冰下湖泊对格陵兰冰盖水文和动态的作用，以便：(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理解；（二）深入了解它们未来对格陵兰和南极洲的影响；（三）生成数据，使冰盖和水文建模者能够改进其对GrIS未来对海平面上升的贡献的预测；（四）为今后在格陵兰进行冰下湖泊勘探奠定科学基础，以调查过去的冰和气候变化以及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.