Rivers on ice: do supraglacial streams evolve like bedrock rivers?

点击翻译按钮获取中文摘要

Supraglacial channels (rivers flowing over ice) are an increasingly common feature of glaciers and ice sheets subjected to a warming climate (Kingslake et al., 2016; Bell et al., 2018; Stokes et al., 2019 ). On mountain glaciers, these channels are important discharge routes for meltwater runoff and may also help connect supraglacial to englacial and subglacial systems, with potential implications for glacier flow. On larger ice sheets and ice shelves, supraglacial channels are closely associated with supraglacial lakes, whose development and drainage can impact on ice sheet mass balance (Bell et al., 2018). Perhaps surprisingly, little is known about how these channels evolve over time, both through melt season and over much longer time-scales. Superficially, these channels appear to be similar to river channels, especially those with bedrock beds, in terms of their morphology and flow dynamics, but many questions remain. For example, we do not know whether they have the same hydraulic geometry as river channels; whether their erosion can be modelled using models created for bedrock rivers; or whether flow velocities can be successfully predicted. Understanding these questions will help predict the total discharge that is carried by these systems and will therefore contribute to our understanding of glacier and ice sheet hydrology. Furthermore, an intriguing unknown is whether these supraglacial channels, which can evolve rapidly to changes in glacier shape, might be useful analogues for bedrock river response to much longer-term base-level changes. The aim of this project is to understand the interactions between flow and channel morphology in supra-glacial channels, and to establish whether their behaviour can be predicted using methods developed for bedrock rivers. This will be established through the following objectives:- Extensive literature review on supraglacial channels- Generate an extensive database of channel morphologies from a range of settings using remote sensing techniques- Undertake a detailed investigation of spatial and temporal changes in channel morphology on a mountain glacier over two field seasons- Comparing whether the morphology and evolution of supraglacial channels is similar to that of bedrock channel analogues.