As the climate warms, meltwater hydrology and water's influence on glacier motion will be an increasingly important aspect of thermal and dynamic processes of large ice masses. With influence on sea level, ocean circulation, and the general climate system, the sliding stability of ice sheets has strong bearing on globally important processes and, thus, warrants full understanding. Unfortunately, in situ investigations of the mechanical linkages between water input and enhanced motion are difficult on thick ice sheets. This problem motivates interest in the hydrology and dynamics of smaller mountain glaciers, where the manageable scale can be utilized to investigate key glaciological processes. We cannot expect to ever fully understand basal motion without advancing our knowledge of the hydrological processes in operation within and beneath glaciers. Understanding of these processes will greatly aid our ability to interpret time/space variability in glacier motion, and ultimately, our ability to predict future changes to glaciers or reconstruct climate history under given glacial scenarios. With these goals in mind, the Principal Investigators will focus on advancing our knowledge of a critical link between hydrological processes and basal sliding: mechanisms of englacial water storage and routing of surface water to the bed. Recent work at Bench Glacier and work at the polythermal Storglaciaren have revealed an englacial network of planar void spaces. Because these are very different glaciers, it is probable that void spaces are a ubiquitous englacial feature. Water has been observed flowing through the voids by both groups. Englacial water flow through a fracture network is a hydrological model in stark contrast to the currently accepted model of an arborescent network of semi-circular conduits (Rothlisberger conduits). The Principal Investigators will test the hypothesis: planar voids are an important part of the englacial hydrological system, capable of storing and routing water from the surface to the bed and perhaps, along the bed. This work will have strong implications for their ability to model and predict the routing of water from a glacier surface to its bed. This work will be conducted at Bench Glacier, Alaska, where there is a known englacial void network. They will test their hypothesis using a series of borehole experiments and geophysical imaging techniques. Many of the geophysical experiments will utilize data acquisition and processing methodologies that have not previously been applied to glaciers. Hence, this work will advance our understanding of both glaciological processes and shallow geophysical imaging.
