Observations of Runoff and Sediment and Dissolved Loads from the Greenland Ice Sheet at Kangerlussuaq, West Greenland, 2007 to 2010

Hasholt, Bent; Mikkelsen, A. B.; Nielsen, Morten Holtegaard; Larsen, Morten Andreas Dahl

doi:10.1127/0372-8854/2012/s-00121

Cited by 60 publications

(106 citation statements)

References 25 publications

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“…As Van de Wal and Russell (1994) already concluded, an uncertainty in meltwater runoff estimates remains due to missing information on the exact extent of the subglacial catchment. Our glacier surface catchment area (12 574 km 2 ) is larger than that reported in previous studies, such as by Mernild et al (2010) (6130 km 2 ) and Hasholt et al (2012) (9743 km 2 ). Given that our 2010 runoff total exceeds the estimated discharge value more than in 2009, and more meltwater originated from a higher elevation in 2010, this could be an indication that the actual drainage area includes less of the upper catchment than assumed in this study.…”

Section: Surface Meltwater Productioncontrasting

confidence: 52%

“…River depth and flow velocity data were gathered at Watson River bridge in Kangerlussuaq and converted into freshwater flux with an estimated uncertainty of 20 % for single values (Hasholt et al, 2012), i.e. 5 % larger than the uncertainty reported by Bartholomew et al (2011) downstream of the bridge, the freshwater from the 25 km long proglacial river originating at the ice sheet margin enters Kangerlussuaq fjord.…”

Section: Observationsmentioning

confidence: 99%

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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

et al. 2012

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Abstract. This study uses data from six on-ice weather stations, calibrated MODIS-derived albedo and proglacial river gauging measurements to drive and validate an energy balance model. We aim to quantify the record-setting positive temperature anomaly in 2010 and its effect on mass balance and runoff from the Kangerlussuaq sector of the Greenland ice sheet. In 2010, the average temperature was 4.9 • C (2.7 standard deviations) above the 1974-2010 average in Kangerlussuaq. High temperatures were also observed over the ice sheet, with the magnitude of the positive anomaly increasing with altitude, particularly in August. Simultaneously, surface albedo was anomalously low in 2010, predominantly in the upper ablation zone. The low albedo was caused by high ablation, which in turn profited from high temperatures and low winter snowfall. Surface energy balance calculations show that the largest melt excess (∼170 %) occurred in the upper ablation zone (above 1000 m), where higher temperatures and lower albedo contributed equally to the melt anomaly. At lower elevations the melt excess can be attributed to high atmospheric temperatures alone. In total, we calculate that 6.6 ± 1.0 km 3 of surface meltwater ran off the ice sheet in the Kangerlussuaq catchment in 2010, exceeding the reference year 2009 (based on atmospheric temperature measurements) by ∼150 %. During future warm episodes we can expect a melt response of at least the same magnitude, unless a larger wintertime snow accumulation delays and moderates the melt-albedo feedback. Due to the hypsometry of the ice sheet, yielding an increasing surface area with elevation, meltwater runoff will be further amplified by increases in melt forcings such as atmospheric heat.

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Section: Surface Meltwater Productioncontrasting

confidence: 52%

Section: Observationsmentioning

confidence: 99%

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

et al. 2012

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“…Where the runoff characteristics of subglacial meltwaters draining from the GrIS are monitored, it is clear that the waters have high sediment [96,98,100] and solute [101, 102, 103•, 104] concentrations, primarily acquired during passage along the ice bed interface. These meltwaters therefore have the potential to provide significant quantities of nutrients to downstream terrestrial and marine ecosystems.…”

Section: Downstream Nutrient Fluxes and Ecosystemsmentioning

confidence: 99%

“…However, two recent studies from west Greenland report much higher rates of erosion:~5 mm year −1 , derived from sediment flux calculations from a large ice sheet catchment [96] and 1-1.8 mm year −1 from cosmogenic dating of exposed glaciated bedrock [97]. Cowton et al [96] argued that large volumes of meltwater accessing the glacier bed, in conjunction with fast hydraulically competent (in terms of sediment transport) drainage routing, large ice thicknesses (100-> 1000 m) and rapid motion (~100 m year −1 ) provide the ideal conditions for both generating and evacuating large volumes of subglacial sediment [98]. Some subsequent studies [76] have argued that these high erosion rates must be indicative of the subglacial drainage evacuating readily mobilised layers of stored subglacial till, as opposed to freshly generated products of erosion.…”

Section: Erosion and Ice Sheet Hydrologymentioning

confidence: 99%

Recent Advances in Our Understanding of the Role of Meltwater in the Greenland Ice Sheet System

Nienow

Sole

Slater

et al. 2017

Curr Clim Change Rep

105

100

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Purpose of the Review This review discusses the role that meltwater plays within the Greenland ice sheet system. The ice sheet's hydrology is important because it affects mass balance through its impact on meltwater runoff processes and ice dynamics. The review considers recent advances in our understanding of the storage and routing of water through the supraglacial, englacial, and subglacial components of the system and their implications for the ice sheet. Recent Findings There have been dramatic increases in surface meltwater generation and runoff since the early 1990s, both due to increased air temperatures and decreasing surface albedo. Processes in the subglacial drainage system have similarities to valley glaciers and in a warming climate, the efficiency of meltwater routing to the ice sheet margin is likely to increase. The behaviour of the subglacial drainage system appears to limit the impact of increased surface melt on annual rates of ice motion, in sections of the ice sheet that terminate on land, while the large volumes of meltwater routed subglacially deliver significant volumes of sediment and nutrients to downstream ecosystems. Summary Considerable advances have been made recently in our understanding of Greenland ice sheet hydrology and its wider influences. Nevertheless, critical gaps persist both in our understanding of hydrology-dynamics coupling, notably at tidewater glaciers, and in runoff processes which ensure that projecting Greenland's future mass balance remains challenging.

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“…River stage has been monitored near the bridge in Kangerlussuaq, southwest Greenland, since 2006 ( Fig. 2; Hasholt et al, 2013). The location of pressure transducers 140-150 m upstream of the bridge in between the two main river channels was chosen to be as close to the river bottom as possible to capture low water levels and sufficiently far upstream to avoid influence of the drop in water level across the stable control section of the river.…”

Section: River Dischargementioning

confidence: 99%

Hypsometric amplification and routing moderation of Greenland ice sheet meltwater release

Mikkelsen²,

Nielsen³

et al. 2017

The Cryosphere

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Abstract. Concurrent ice sheet surface runoff and proglacial discharge monitoring are essential for understanding Greenland ice sheet meltwater release. We use an updated, wellconstrained river discharge time series from the Watson River in southwest Greenland, with an accurate, observation-based ice sheet surface mass balance model of the ∼ 12 000 km 2 ice sheet area feeding the river. For the 2006-2015 decade, we find a large range of a factor of 3 in interannual variability in discharge. The amount of discharge is amplified ∼ 56 % by the ice sheet's hypsometry, i.e., area increase with elevation. A good match between river discharge and ice sheet surface meltwater production is found after introducing elevationdependent transit delays that moderate diurnal variability in meltwater release by a factor of 10-20. The routing lag time increases with ice sheet elevation and attains values in excess of 1 week for the upper reaches of the runoff area at ∼ 1800 m above sea level. These multi-day routing delays ensure that the highest proglacial discharge levels and thus overbank flooding events are more likely to occur after multiday melt episodes. Finally, for the Watson River ice sheet catchment, we find no evidence of meltwater storage in or release from the en-and subglacial environments in quantities exceeding our methodological uncertainty, based on the good match between ice sheet runoff and proglacial discharge.

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Observations of Runoff and Sediment and Dissolved Loads from the Greenland Ice Sheet at Kangerlussuaq, West Greenland, 2007 to 2010

Cited by 60 publications

References 25 publications

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

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

Recent Advances in Our Understanding of the Role of Meltwater in the Greenland Ice Sheet System

Hypsometric amplification and routing moderation of Greenland ice sheet meltwater release

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