Determination of groundwater impact on runoff by a hydro(geo)logical and isotopic approach in the glaciated Austrelovén watershed (Spitsbergen)

Mélanie Quenet, Christelle Marlin, Aurélie Noret, Gaël Monvoisin, Madeleine Griselin, Florian Tolle, Corinne Le Gal La Salle, Patrick Verdoux, Jean-Michel Friedt

Dans les comptes rendus d’articles de la conférence: GeoMontréal 2013: 66th Canadian Geotechnical Conference; 11th joint with IAH-CNC

Session: Isotope Tracing II

ABSTRACT: In glaciated watersheds of the High Arctic, the quantification of water components involved in the runoff is quite complex and requires a combination of several approaches. Amongst which, the natural hydrochemical and isotopic tracers are powerful tools to identify the mixing of the different end-members if they are characterized by geochemical signatures significantly different. Along the western coast of Spitsbergen, the Austrelovén glacier watershed (10 km²), situated in a continuous permafrost area is representative of small watersheds with continental terminus. Besides, this glacier has the particularity to present a subglacial perennial spring which leads to the growing of icings during winter. Its melting contributes consistently to the flows during summer. However, the origin of the subglacial runoff is still not well known. Associated to this subglacial reservoir discharge, different water-bodies provide water and solutes to the rivers: rainfall, meltwater and groundwater. Indeed, the thawing of the active layer forms a temporary water-table above the permafrost that may exchange with the stream water. In order to decompose the flows at the outlet of the Austrelovén glacier watershed, a set of 151 water samples were taken from the supra-permafrost water-table, springs, ponds, subglacial 182H of the H2O molecule, 13C and A14C of DIC, 87Sr/86Sr) are used to discuss the origin of the different water end-members and to investigate the river water/groundwater exchanges (end-members signatures, water-rock interactions and solute acquisition processes). The predominant water-type is sulfate-bicarbonate calcium. The stable isotopes contents of the water molecule show that the s18O between -8 and --18O between -12 and -18O between -16 and -87Sr/86Sr show that all analyzed waters are radiogenic and seems to confirm that the outlet signature (87Sr/86Sr = 0.730) is a mixture between the supra-permafrost groundwater (87Sr/86Sr = 0.750) and the subglacial river (87Sr/86Sr = 0.726). The origin of the subglacial river 13C and A1413C between -4 and -14C between 19 and 26 pMC). These results are consistent with a long residence time of subglacial meltwater. The latter is likely to discharge from a confined aquifer beneath the glacier.

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