Investigating meltwater flow beneath the Greenland Ice Sheet using a multi-tracer approach

The Greenland Ice Sheet is the main reservoir of ice in the northern hemisphere capable of affecting sea level in the 21st Century. Measurements of the elevation of the ice sheet surface from aircraft now provide a much better picture of the whether the ice sheet is graining or losing mass. However, until there is a better understanding of how ice flows from the ice sheet interior to the ocean, models that aim to predict the response of the Greenland Ice Sheet to climate change and the impact on sea level are unlikely to produce accurate estimates. One of the least poorly understood aspects of ice flow is how meltwater lubrication at the ice sheet sole might affect the rate of ice discharge to the ocean. Recent research has shown that the input of surface meltwater to the ice sheet bed in summer causes considerable ice speed up. Exactly how meltwater flows at the bed (does it flow in discrete channels or does it spread out and flow in a more diffuse manner?) is crucial to understanding how the ice sheet might respond to increased melt inputs in a warming climate. Currently, little is known about basal meltwater routing because the vast amounts of meltwater prevent the use of traditional tracing techniques (e.g. dye tracing). This project aims to apply novel tracing methods which will survive large scale dilution, and which can be injected to holes (moulins) on the glacier surface and detected when the water emerges at the ice sheet front. Some of these techniques have been using widely in oceanography to trace currents across ocean basins. Our tracer experiments will provide new information regarding characteristics of meltwater flow paths and their temporal/spatial variations at the bed of the ice sheet and provide detailed measurements (e.g. pressure) of along-flow path characteristics. Comparison of our tracer results (e.g. water flow speeds, pressure conditions in channels) with ice velocity data from the same glacier will help identify linkages between meltwater routing and ice flow mechanisms, and will generate a unique dataset for future numerical modelling studies aimed at quantifying the future contribution of the Greenland Ice Sheet to global sea level rise.level rise.