Twenty-one years of mass balance observations along the K-transect, West Greenland

Wal, R. S. W. van de; Boot, W.; Smeets, C. J. P. P.; Snellen, Henk; Broeke, M. R. van den; Oerlemans, J.

doi:10.5194/essd-4-31-2012

Cited by 103 publications

(92 citation statements)

References 20 publications

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“…Observational records along the nearby K-transect have shown that the annual ELA has varied from ∼1400 to 1800 m (van de Wal et al, 2012). If the surface velocity and the ice sheet geometry are in a state of balance and reflect steady state flow dynamics over a decadal time scale across the study area, this implies that increased rates of sliding are sufficiently insensitive to seasonal variations in meltwater input so as to produce the observed ice geometry.…”

Section: Enhanced Basal Slipmentioning

confidence: 98%

“…Meltwater-induced seasonal variations in ice motion have been observed to elevations reaching ∼1500-1600 m (Bartholomew et al, 2011;Palmer et al, 2011). Given this evidence, the long term measured ELA of 1553 m (van de Wal et al, 2012) appears to serve as a plausible limit of the inland extent of seasonal surface meltwater routing to the bed. Its location also aligns with the greatest rate of velocity change along the flowline (Figure 8), suggesting that the increase in velocity is related to the introduction of surface meltwater to the bed.…”

Section: Enhanced Basal Slipmentioning

confidence: 99%

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Force Balance along Isunnguata Sermia, West Greenland

2016

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Ice flows when gravity acts on gradients in surface elevation, producing driving stresses. In the Isunnguata Sermia and Russell Glacier catchments of western Greenland, a 50% decline in driving stress along a flow line is juxtaposed with increasing surface flow speed. Here, these circumstances are investigated using modern observational data sources and an analysis of the balance of forces. Stress gradients in the ice mass and basal drag which resist the local driving stress are computed in order to investigate the underlying processes influencing the velocity and stress regimes. Our results show that the largest resistive stress gradients along the flowline result from increasing surface velocity. However, the longitudinal coupling stresses fail to exceed 15 kPa, or 20% of the local driving stress. Consequently, computed basal drag declines in proportion to the driving stress. In the absence of significant resistive stress gradients, other mechanisms are therefore necessary to explain the observed velocity increase despite declining driving stress. In the study area, the observed velocity-driving stress feature occurs at the long-term mean position of the equilibrium line of surface mass balance. We hypothesize that this position approximates the inland limit where seasonal surface meltwater penetrates the bed, and that the increased surface velocity reflects enhanced basal motion associated with these meltwater perturbations.

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Section: Enhanced Basal Slipmentioning

confidence: 98%

Section: Enhanced Basal Slipmentioning

confidence: 99%

Force Balance along Isunnguata Sermia, West Greenland

2016

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“…Figure 9 illustrates the seasonal cycle for SMB and precipitation, runoff and melt components over both the 1961-1990and 1996-2008periods. For the 1961-1990 period, monthly SMB is generally positive, adding between 30 and 60 Gt to the ice sheet except for the peak melt period (June-August) where, despite increased precipitation, there is a net mass loss due to runoff.…”

Section: Seasonal Cyclementioning

confidence: 99%

“…The Regional Atmosphere Climate Model version 2.1 (RACMO2.1) was developed by the Royal Netherlands Meteorological Institute (KNMI) (van Meijgarrd et al, 2008). Adjustments specific to the Arctic environment have been made to the original model to produce RACMO2/GR.…”

Section: Racmomentioning

confidence: 99%

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Surface mass balance model intercomparison for the Greenland ice sheet

et al. 2013

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Abstract. A number of high resolution reconstructions of the surface mass balance (SMB) of the Greenland ice sheet (GrIS) have been produced using global re-analyses data extending back to 1958. These reconstructions have been used in a variety of applications but little is known about their consistency with each other and the impact of the downscaling method on the result. Here, we compare four reconstructions for the period 1960-2008 to assess the consistency in regional, seasonal and integrated SMB components. Total SMB estimates for the GrIS are in agreement within 34 % of the four model average when a common ice sheet mask is used. When models' native land/ice/sea masks are used this spread increases to 57 %. Variation in the spread of components of SMB from their mean: runoff 42 % (29 % native masks), precipitation 20 % (24 % native masks), melt 38 % (74 % native masks), refreeze 83 % (142 % native masks) show, with the exception of refreeze, a similar level of agreement once a common mask is used. Previously noted differences in the models' estimates are partially explained by ice sheet mask differences. Regionally there is less agreement, suggesting spatially compensating errors improve the integrated estimates.Modelled SMB estimates are compared with in situ observations from the accumulation and ablation areas. Agreement is higher in the accumulation area than the ablation area suggesting relatively high uncertainty in the estimation of ablation processes. Since the mid-1990s each model estimates a decreasing annual SMB. A similar period of decreasing SMB is also estimated for the period 1960-1972. The earlier decrease is due to reduced precipitation with runoff remaining unchanged, however, the recent decrease is associated with increased precipitation, now more than compensated for by increased melt driven runoff. Additionally, in three of the four models the equilibrium line altitude has risen since the mid-1990s, reducing the accumulation area at a rate of approximately 60 000 km 2 per decade due to increased melting. Improving process representation requires further study but the use of a single accurate ice sheet mask is a logical way to reduce uncertainty among models.

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Future climate warming increases Greenland ice sheet surface mass balance variability

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Vizcaíno

Lipscomb

et al. 2014

Geophysical Research Letters

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The integrated surface mass balance (SMB) of the Greenland ice sheet (GrIS) has large interannual variability. Long‐term future changes to this variability will affect GrIS dynamics, freshwater fluxes, regional oceanography, and detection of changes in ice volume trends. Here we analyze a simulated 1850–2100 GrIS SMB time series from the Community Earth System Model, currently the only global climate model that realistically simulates GrIS SMB. We find a significant increase in interannual integrated SMB variability over time, which we attribute primarily to a shift to a high‐variability melt‐dominated SMB regime due to GrIS ablation area growth. We find temporal increases to characteristic ablation and accumulation area‐specific SMB variabilities to be of secondary importance. Since ablation area SMB variability is driven largely by variability in summer surface melt, variability in the climate processes regulating the energy fluxes that control melting will likely increasingly determine future GrIS SMB variability.

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Twenty-one years of mass balance observations along the K-transect, West Greenland

Cited by 103 publications

References 20 publications

Force Balance along Isunnguata Sermia, West Greenland

Force Balance along Isunnguata Sermia, West Greenland

Surface mass balance model intercomparison for the Greenland ice sheet

Future climate warming increases Greenland ice sheet surface mass balance variability

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