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

冰上水道（在冰上流动的河流）是受气候变暖影响的冰川和冰盖越来越常见的特征（Kingslake等人，2016; Bell等人，2018; Stokes等人，2019年）。在高山冰川上，这些通道是融水径流的重要排泄路线，也可能有助于连接冰上系统与冰内系统和冰下系统，对冰川流动有潜在的影响。在较大的冰盖和冰架上，冰上水道与冰上湖泊密切相关，其发展和排水会影响冰盖质量平衡（Bell等人，2018年）。也许令人惊讶的是，很少有人知道这些渠道如何随着时间的推移，无论是通过融化季节和更长的时间尺度。从表面上看，这些通道在形态和水流动力学方面与河流通道相似，特别是那些有基岩的通道，但仍存在许多问题。例如，我们不知道它们是否具有与河道相同的水力几何形状;它们的侵蚀是否可以使用为基岩河流创建的模型进行建模;或者流速是否可以成功预测。了解这些问题将有助于预测这些系统所承载的总流量，从而有助于我们对冰川和冰盖水文学的理解。此外，一个有趣的未知数是，这些冰上通道，可以迅速演变为冰川形状的变化，可能是有用的类似物基岩河流响应更长期的基准面变化。该项目的目的是了解流动和渠道形态之间的相互作用，在冰上渠道，并确定其行为是否可以使用基岩河流开发的方法进行预测。这将通过以下目标建立：-广泛的文献审查冰上渠道-生成一个广泛的数据库的通道形态从一系列设置使用遥感技术-进行详细调查的空间和时间变化的通道形态的山区冰川在两个领域的季节-比较是否冰上渠道的形态和演变是类似的基岩渠道类似物。

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.