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

点击翻译按钮获取中文摘要

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.