Evidence of meltwater retention within the Greenland ice sheet

Abstract

Abstract. Greenland ice sheet mass losses have increased in recent decades with approximately half of these attributed to increased surface meltwater runoff. However, controls on ice sheet water release, and the magnitude of englacial storage, firn densification, internal refreezing and other hydrologic processes that delay or reduce true water export to the global ocean remain poorly understood. This problem is amplified by scant hydrometerological measurements. Here, ice sheet surface meltwater runoff and proglacial river discharge determined between 2008 and 2010 for three sites near Kangerlussuaq, western Greenland were used to establish the water budget for a small ice sheet watershed. The water budget could not be closed in the three years, even when uncertainty ranges were considered. Instead between 12% and 53% of ice sheet surface runoff is retained within the glacier each melt year (time between onset of ice sheet runoff in two consecutive years). Evidence of the ice sheet summer meltwater escaping during the cold-season suggests that the Greenland ice sheet cryo-hydrologic system may remain active year round.