Accumulation over the Greenland ice sheet from historical and recent records

Bales, R. C.; McConnell, Joseph R.; Mosley‐Thompson, Ellen; Csathó, Beáta

doi:10.1029/2001jd900153

Cited by 118 publications

(125 citation statements)

References 23 publications

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“…The magnitude and inter-annual variation in precipitation for Tasillaq are generally ∼20% greater than for the ERA-40 accumulation for the south east GrIS. The south east GrIS has both the highest absolute precipitation and greatest variability in precipitation of the GrIS (Bales et al, 2001;Hanna et al, 2006Hanna et al, , 2008 and so for other regions of the ice sheet, uncertainty due to interannual precipitation variations will also be less.…”

Section: Constraint On Dynamic Thinningmentioning

confidence: 99%

Testing hypotheses of the cause of peripheral thinning of the Greenland Ice Sheet: is land-terminating ice thinning at anomalously high rates?

et al. 2008

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Abstract.Recent observations have shown that the periphery of the Greenland ice sheet (GrIS) is thinning rapidly and that this thinning is greatest around marine-terminating outlet glaciers. Several theories have been proposed which provide a link between climate and ice thinning. We present surface elevation change (dh/dt) data from NASA's Program for Arctic Regional Climate Assessment (PARCA) laser altimetry surveys for fourteen and eleven of the largest outlet glaciers in Southern Greenland from 1993 to 1998 and 1998 to 2006 respectively to test the applicability of these theories to the GrIS.Initially, outlet glacier dh/dt data are compared with data from concurrent surveys over inland ice (slow flowing ice that is not obviously draining into an outlet glacier) to confirm the effect of ice flow on surface thinning rates. Landterminating and marine-terminating outlet glacier dh/dt data are then compared from 1993 to 1998 and from 1998 to 2006. Finally, ablation anomalies (the difference between the "normal" ablation rate from 1970 to 2000 and the ablation rate in the time period of interest) calculated with a positive degree day model are compared to both marine-terminating and land-terminating outlet glacier dh/dt data.Our results support earlier conclusions that certain marineterminating outlet glaciers have thinned much more than land-terminating outlet glaciers during both time periods. Furthermore we show that these differences are not limited to the largest, fastest-flowing outlet glaciers -almost all marine-terminating outlet glaciers are thinning more than land-terminating outlet glaciers. There was a four fold increase in mean marine-terminating outlet glacier thinning Correspondence to: A. Sole (a.j.sole@bristol.ac.uk) rates below 1000 m elevation between the periods 1993 to 1998 and 1998 to 2006, while thinning rates of landterminating outlet glaciers remained statistically unchanged. This suggests that a change in a controlling mechanism specific to the thinning rates of marine-terminating outlet glaciers occurred in the late 1990s and that this change did not affect thinning rates of land-terminating outlet glaciers.Thinning rates of land-terminating outlet glaciers are statistically the same as ablation anomalies, while thinning rates of marine-terminating outlet glaciers are not. Thinning of land-terminating outlet glaciers therefore seems to be a response to changes in local mass balance (principally increases in air temperature) while thinning of marineterminating outlet glaciers is principally controlled by ice dynamics. The mechanism by which this dynamic thinning occurs is still not clear although its association with marineterminating outlet glaciers suggests perturbations at marine termini (calving) as the likely cause.

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Section: Constraint On Dynamic Thinningmentioning

confidence: 99%

Testing hypotheses of the cause of peripheral thinning of the Greenland Ice Sheet: is land-terminating ice thinning at anomalously high rates?

et al. 2008

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“…Bales et al (2001Bales et al ( , 2009 and Cogley (2004) have collated the available data. In the ablation area stake measurements are taken but due to the logistical difficulties of repeat visits there are fewer of this type Each observation provides an average yearly SMB over a several year period.…”

Section: Validation Datamentioning

confidence: 99%

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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“…1, yellow dots). This data set is based on a compilation of deep snow pit and firn core measurements presented in Bales et al (2001Bales et al ( , 2009, selected for the period 1979-2012, when temporal overlap occurs between model and observations.…”

Section: Observational Datamentioning

confidence: 99%

Evaluation of the updated regional climate model RACMO2.3: summer snowfall impact on the Greenland Ice Sheet

et al. 2015

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Abstract. We discuss Greenland Ice Sheet (GrIS) surface mass balance (SMB) differences between the updated polar version of the RACMO climate model (RACMO2.3) and the previous version (RACMO2.1). Among other revisions, the updated model includes an adjusted rainfall-to-snowfall conversion that produces exclusively snowfall under freezing conditions; this especially favours snowfall in summer. Summer snowfall in the ablation zone of the GrIS has a pronounced effect on melt rates, affecting modelled GrIS SMB in two ways. By covering relatively dark ice with highly reflective fresh snow, these summer snowfalls have the potential to locally reduce melt rates in the ablation zone of the GrIS through the snow-albedo-melt feedback. At larger scales, SMB changes are driven by differences in orographic precipitation following a shift in large-scale circulation, in combination with enhanced moisture to precipitation conversion for warm to moderately cold conditions. A detailed comparison of model output with observations from automatic weather stations, ice cores and ablation stakes shows that the model update generally improves the simulated SMBelevation gradient as well as the representation of the surface energy balance, although significant biases remain.

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Accumulation over the Greenland ice sheet from historical and recent records

Cited by 118 publications

References 23 publications

Testing hypotheses of the cause of peripheral thinning of the Greenland Ice Sheet: is land-terminating ice thinning at anomalously high rates?

Testing hypotheses of the cause of peripheral thinning of the Greenland Ice Sheet: is land-terminating ice thinning at anomalously high rates?

Surface mass balance model intercomparison for the Greenland ice sheet

Evaluation of the updated regional climate model RACMO2.3: summer snowfall impact on the Greenland Ice Sheet

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