Glacial meltwater and groundwater interactions : evidence from the Virkisjokull observatory in Iceland

There is growing recognition of the important role that groundwater may have in buffering changes in river discharge due to increased melting of glaciers. Glacial deposits, particularly proglacial deposits and outwash plains can form significant aquifers and contain groundwater stores that are rarely quantified. In addition, interaction of basal melting of glaciers with groundwater can help to sustain flow through prolonged cold winters. The multidisciplinary BGS observatory at Virkisjökull in Iceland provides an excellent opportunity to characterise and quantify glacial meltwaters and groundwater. Glacier meltwater has been measured since September 2011, and precipitation and temperature from weather stations at varying altitudes since September 2009. Meltwaters and groundwater in the proglacial environment have been sampled periodically and analysed for inorganic chemistry, CFC, SF6 and stable isotopes to help understand the origin and flow paths of meltwaters and groundwater. The proglacial deposits have been mapped and the permeability of targeted deposits characterised. Initial findings show that the outwash plain provides a significant highly permeable aquifer, and is recharged locally from precipitation, with a growing influence of meltwater close to the meltwater channel. Shallow groundwater from snow melt within the catchment provides significant flow to the meltwater channels in spring, but in the prolonged winter, basal meltwater, possibly linked with sub glacial groundwater, helps to sustain flow in the meltwater channels. This initial study has led to the design of a more detailed experiment in the summer of 2012 involving the drilling and instrumentation of a targeted network of piezometers across the sandur and proglacial area