Meltwater flow through a rapidly deglaciating glacier and foreland catchment system, Virkísjökull, SE Iceland

This study characterizes the glacial and proglacial hydrology of a rapidly deglaciating system at Virkísjökull in SE Iceland, to determine the water flux through the glacier and proglacial area. This was achieved using dye tracer tests, river discharge measurements and studies of conduits within the foreland and glacier using ground-penetrating radar (GPR). Tracer testing through the glacial system via a moulin demonstrated rapid flow of 0.58 m s–1, which was comparable to the flow rates within the proglacial river, and is at the higher end of velocities observed in glacial conduits. A subsequent test from this moulin at the end of the winter season demonstrated that the conduit system was fully open at this time, suggesting that it may not close during the winter. A tracer test through the proglacial foreland showed that the large proglacial lake does not substantially attenuate flow and revealed the presence of a relic conduit system enabling rapid water transit through this area, with velocities of 0.03 m s–1. The proglacial river is highly responsive to melt as a result of fully developed conduits in both the subglacial and proglacial areas. Given that in the proglacial foreland there are the remains of the previous margin of the glacier, these conduits may be a relic of a previous subglacial pathway that has been abandoned in the foreland. The existence of relic conduits may appear in other deglaciating ice-cored forelands and can have a significant impact on the hydrological connectivity and therefore modelling of river discharge in similar catchments.