Calibration and evaluation of a high-resolution surface mass-balance model for Paakitsoq, West Greenland

Banwell, Alison F.; Willis, Ian; Arnold, Neil; Messerli, Alexandra; Rye, C.; Tedesco, Marco; Ahlstrøm, Andreas P.

doi:10.3189/2012jog12j034

Cited by 18 publications

(47 citation statements)

References 86 publications

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“…The combination of DEM‐derived channel profiles and visual record of abandoned channels provide a record of time‐evolving fluvial erosion tiled densely over the ablation zone. In combination with ice flow models [e.g., Banwell et al , ] that would provide the appropriate background state for channel profile analysis, analysis of stream profile evolution from DEMs made at multiple times during a melt season could constrain the interplay between ice flow and melting on ∼1 − 10 km scales. We have focused on steady state profiles here, but slope transients arising from sudden changes in base level (such as lake drainage) [ Das et al , ], spatially localized ice sheet acceleration or uplift [e.g., Ryser et al , ] may also be encoded in stream profiles, as is argued for some bedrock landscapes [e.g., Willett et al , ].…”

Section: Discussionmentioning

confidence: 99%

Fluvial supraglacial landscape evolution on the Greenland Ice Sheet

Karlstrom

Yang

2016

Geophysical Research Letters

101

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Supraglacial stream networks incise via thermal erosion of underlying ice, reflecting a balance between localized fluvial incision and dynamic topography from underlying ice flow. We analyze high‐resolution digital elevation models of the ice surface and bedrock in the southwest Greenland Ice Sheet from 1000‐1600 m elevation to quantify the importance of fluvial erosion. At wavelengths greater than ice thickness, bedrock dominates surface topography so supraglacial drainage basins are fixed spatially. At smaller wavelengths, fluvial erosion significantly affects topography. Stream longitudinal profiles exhibit positive mean curvature and consistent power law scaling between local channel slope and drainage area, suggestive of adjustment toward topographic steady state. We interpret these observations with a model for fluvial thermal erosion on top of a flowing ice substrate that predicts concave up steady state longitudinal profiles, where average concavity is most sensitive to melt rate and the relative magnitudes of ice flow and fluvial erosion.

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Section: Discussionmentioning

confidence: 99%

Fluvial supraglacial landscape evolution on the Greenland Ice Sheet

Karlstrom

Yang

2016

Geophysical Research Letters

101

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“…The full model is run from 1 September 2004 to 31 August 2005. This year was selected as it is one for which the SMB model was calibrated [ Banwell et al, ]. However, following Banwell et al [], results are only analyzed from 12 May 2005 to 31 August 2005, which spans the melt season.…”

Section: Methodsmentioning

confidence: 99%

Moulin density controls drainage development beneath the Greenland ice sheet

et al. 2016

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Uncertainty remains about how the surface hydrology of the Greenland ice sheet influences its subglacial drainage system, affecting basal water pressures and ice velocities, particularly over intraseasonal and interseasonal timescales. Here we apply a high spatial (200 m) and temporal (1 h) resolution subglacial hydrological model to a marginal (extending~25 km inland), land-terminating,~200 km 2 domain in the Paakitsoq region, West Greenland. The model is based on that by Hewitt (2013) but adapted for use with both real topographic boundary conditions and calibrated modeled water inputs. The inputs consist of moulin hydrographs, calculated by a surface routing and lake-filling/draining model, which is forced with distributed runoff from a surface energy-balance model. Results suggest that the areal density of lake-bottom moulins and their timing of opening during the melt season strongly affects subglacial drainage system development. A higher moulin density causes an earlier onset of subglacial channelization (i.e., water transport through channels rather than the distributed sheet), which becomes relatively widespread across the bed, whereas a lower moulin density results in a later onset of channelization that becomes less widespread across the bed. In turn, moulin density has a strong control on spatial and temporal variations in subglacial water pressures, which will influence basal sliding rates, and thus ice motion. The density of active surface-to-bed connections should be considered alongside surface melt intensity and extent in future predictions of the ice sheet's dynamics.

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“…The Paakitsoq region includes the area for which the SMB model was calibrated and evaluated in Banwell et al . [], and also encompasses the smaller area for which the surface routing and lake filling model was calibrated and evaluated in Banwell et al . [].…”

Section: Study Sitementioning

confidence: 99%

Modeling subglacial water routing at Paakitsoq, W Greenland

2013

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[1] The functioning of the Greenland Ice Sheet's subglacial drainage system and its effect on ice dynamics have been inferred largely from hypothetical hydrology dynamics models and from analysis of satellite data and in situ GPS measurements. Despite this, there is still uncertainty about how the surface hydrology interacts with the subglacial drainage system and affects basal water pressures and ice flow, especially over annual time scales. To address this, we developed a high spatial (100 m) and temporal (1 h) resolution, distributed, physically based, subglacial hydrological model, and applied it to the Paakitsoq region, western Greenland. The model is driven with moulin input hydrographs calculated by a surface routing and lake filling/draining model, forced ultimately with distributed hourly runoff calculated by a surface mass balance model. Key outputs from the model are spatially and temporally varying subglacial water pressures and proglacial stream hydrographs. Early in the melt season, short spikes in water pressure lasting less than a day occur as a result of lake drainage events. During midsummer, there are sustained periods of high water pressure lasting days to weeks, even at times when the subglacial system is inferred to be predominantly efficient. Later in the summer, large diurnal fluctuations in water pressure occur with peaks regularly exceeding ice overburden pressure superimposed on a gradually declining trend. These phenomena support the results of previous hypothetical modeling efforts and inferences drawn from GPS measurements.

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Calibration and evaluation of a high-resolution surface mass-balance model for Paakitsoq, West Greenland

Cited by 18 publications

References 86 publications

Fluvial supraglacial landscape evolution on the Greenland Ice Sheet

Fluvial supraglacial landscape evolution on the Greenland Ice Sheet

Moulin density controls drainage development beneath the Greenland ice sheet

Modeling subglacial water routing at Paakitsoq, W Greenland

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