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

快速排水的冰下湖泊对格陵兰冰盖水文和动力学的影响

• 批准号: NE/X000257/1
• 负责人: Stephen Livingstone
• 金额: $ 87.66万
• 依托单位: University of Sheffield
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FX000257%2F1
• 关键词: influence; fast; draining; subglacial; lakes

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.

冰下水文是格陵兰冰盖质量损失的关键控制因素，它通过影响消融区的冰运动和海洋终止冰川的锋面消融来实现。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构造、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，也是其他行星上生命的类似物。大量水的局部储存和下游排水调节了基础水文和地球化学循环/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。排水事件也可以形成通道，切割成冰或进入河床，并将大量的水和沉积物输送到下游。最后，冰川前陆的洪水爆发对下游的生活和基础设施构成了重大威胁。尽管有大量文献记载，南极冰盖下存在数百个冰下湖泊，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假设它们是稀缺的。然而，我们团队成员最近的工作表明，湖泊在格陵兰冰盖下分布广泛，而且可能是高度动态的特征，与南极洲相反，湖泊由冰面融化而成，可以在几周内迅速流失。因此，它们代表了格陵兰和南极洲冰下湖泊如何在更温暖的世界中表现的重要端元，因为表面融化变得更加普遍，进入更宽的床，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相结合，以准确确定这些环境的特性，并评估其对冰盖冰下水文和冰动力的影响。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Isunnguata Sermia下面发现的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。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：㈠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认识; ㈡深入了解其今后对格陵兰和南极的影响，（iii）生成数据，使冰盖和水文模型制作者能够更好地预测全球气候信息系统对海平面上升的未来影响，（iv）为格陵兰未来的冰下湖泊勘探奠定科学基础，以调查过去的冰和气候变化，并探索冰下生物和地球化学通量。