River morphodynamic responses to climate change in Greenland

Rivers in Greenland are responding to some of the most rapid and extreme climate change on Earth. Rapidly rising air temperatures in the arctic are causing accelerated ice sheet and mountain glacier melt and permafrost thaw. This melt and thaw is not only generating meltwater but also releasing sediment, which fundamentally affects river geomorphology and hydraulics. Fluvially-transported sediment is a great concern for infrastructure such as hydropower installations and for fishing, both of which are major contributors to the GDP of Greenland. Given the space and time problems of understanding the changes occurring in Greenland’s rivers, numerical modelling is urgently required to quantify the effects of increased meltwater and sediment discharges in river planform, geomorphology, hydraulics and sediment transport, all of which are inter-linked. This project will utilise data from Greenland’s (only) two gauged rivers to parameterise a model and then run scenario experiments with increased meltwater and sediment fluxes.

This project will use a state-of-the-art morphodynamic computational fluid dynamics model (code) to conduct scenario-based experiments of Greenland rivers with increased meltwater and sediment fluxes. The model will be parameterised with river gauged data (daily water and sediment discharge), field data (distributed roughness and grain size distributions) and remote-sensing data (river planform and geomorphology). The scenarios of meltwater increases will be informed by predicted climate change and ice sheet and mountain glacier mass loss estimates. Sediment availability will be estimated as a function of subglacial discharge and as a function of river channel bank composition. For the latter a permafrost distribution and characterisation map will inform scenarios of changing river bank cohesion. Major outcomes therefore will be space- and time-distributed hydraulics, sediment transport (suspended load and bedload) and river bed elevation (i.e. erosion and deposition) estimates for several Greenland rivers under scenarios of climate change, increased meltwater and increased sediment availability. The sediment delivery ratio; i.e. that proportion making it out of catchments to the lowlands/fjords/coast will be of particular interest and might be one of several metrics by which the response of rivers around Greenland to climate change can be compared.