A new cycle of jökulhlaups at Russell Glacier, Kangerlussuaq, West Greenland

Abstract

ABSTRACT. Jö kulhlaups in 2007 and 2008 from an ice-dammed lake at the northern margin of Russell Glacier, West Greenland, marked the onset of a renewed jö kulhlaup cycle after 20 years of stability. We present a record of successive ice-dammed lake drainage events and associated ice-margin dynamics spanning $25 years. Robust calculations of lake volumes and peak discharges are made, based on intensive field surveys and utilizing high-spatial-resolution orthophotographs of the lake basin and ice margin. These data enable identification of controls on the behaviour of the ice-dammed lake and provide the first field-based examination of controls on jö kulhlaup magnitude and frequency for this system. We find that Russell Glacier jö kulhlaups have a much higher peak discharge than predicted by the Clague-Mathews relationship, which we attribute to an unusually short englacial/subglacial routeway and the presence of a thin ice dam that permits incomplete sealing of jö kulhlaup conduits between lake drainage events. Additionally, we demonstrate that the passage of jökulhlaups through an interlinked system of proglacial bedrock basins produces significant attenuation of peak discharge downstream. We highlight that improved understanding of jökulhlaup dynamics requires accurate information about ice-dammed lake volume and ice-proximal jö kulhlaup discharge.

Evidence of meltwater retention within the Greenland ice sheet

“…It is known that meltwater may be retained on the ice sheet surface in lakes (Selmes et al, 2011;Sundal et al, 2009) and percolate into firn layers . However, evidence presented in this study suggests that meltwater transported through englacial conduits (Catania and Neumann, 2010;Catania et al, 2008) to storage cavities in englacial and subglacial environments may remain there until short thaw events presumably trigger its release.…”

“…However, this model agreement masks large differences in parameterization, for example, different treatment of meltwater refreezing in firn results in 13-49 % retention of average meltwater production (Box et al, 2006;Ettema et al, 2009;Fettweis, 2007;Hanna et al, 2008;Janssens and Huybrechts, 2000;Mernild and Liston, 2012). Furthermore, all models ignore water storage in supraglacial lakes, which are abundant on the Greenland ice sheet (Selmes et al, 2011).…”

“…1). Site AK4 is upstream and therefore unaffected by episodic jökulhlaups from a large proglacial lake in this region (e.g., Russell et al, 2011). Meteorological observations on the ice sheet were acquired at three AWSs labeled S5, KAN_L, and S6 in Fig.…”

“…In southwestern Greenland, an area with prominent surface meltwater lakes (Selmes et al, 2011), 40 % of lakes store water and freeze up in winter months with remaining lakes either draining slowly (37 %), quickly (14 %), or its state cannot be determined (8 %) (Selmes et al, 2013). Sudden drainage of ice sheet supra- (Bartholomew et al, 2011;Doyle et al, 2013), en-, sub- (Mathews, 1963), and proglacial meltwater lakes (Mernild and Hasholt, 2009;Russell, 2009;Russell et al, 2011) can result in pronounced river discharge anomalies.…”

Large surface meltwater discharge from the Kangerlussuaq sector of the Greenland ice sheet during the record-warm year 2010 explained by detailed energy balance observations

“…Also, the runoff values for the glacier do not consider the sinks and sources in the proglacial tundra, such as precipitation, evaporation, and interaction with groundwater. A further source of mismatch between the two records is potential storage in supra-and sub-glacial melt lakes, including the ice-dammed marginal lake as documented by Russell et al (2011).…”