scholarly journals Greenland ice sheet surface mass balance 1991–2000: Application of Polar MM5 mesoscale model and in situ data

2004 ◽  
Vol 109 (D16) ◽  
Author(s):  
Jason E. Box
Keyword(s):  
Mass Balance ◽  
Mesoscale Model ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Sheet Surface ◽  
In Situ Data

scholarly journals Greenland ice sheet surface mass balance: evaluating simulations and making projections with regional climate models

2012 ◽  
Vol 6 (6) ◽  
pp. 1275-1294 ◽  
Author(s):  
J. G. L. Rae ◽  
G. Aðalgeirsdóttir ◽  
T. L. Edwards ◽  
X. Fettweis ◽  
J. M. Gregory ◽  
...  
Keyword(s):  
Mass Balance ◽  
Sea Level ◽  
Climate Models ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Regional Climate Models ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Sheet Surface

Abstract. Four high-resolution regional climate models (RCMs) have been set up for the area of Greenland, with the aim of providing future projections of Greenland ice sheet surface mass balance (SMB), and its contribution to sea level rise, with greater accuracy than is possible from coarser-resolution general circulation models (GCMs). This is the first time an intercomparison has been carried out of RCM results for Greenland climate and SMB. Output from RCM simulations for the recent past with the four RCMs is evaluated against available observations. The evaluation highlights the importance of using a detailed snow physics scheme, especially regarding the representations of albedo and meltwater refreezing. Simulations with three of the RCMs for the 21st century using SRES scenario A1B from two GCMs produce trends of between −5.5 and −1.1 Gt yr−2 in SMB (equivalent to +0.015 and +0.003 mm sea level equivalent yr−2), with trends of smaller magnitude for scenario E1, in which emissions are mitigated. Results from one of the RCMs whose present-day simulation is most realistic indicate that an annual mean near-surface air temperature increase over Greenland of ~ 2°C would be required for the mass loss to increase such that it exceeds accumulation, thereby causing the SMB to become negative, which has been suggested as a threshold beyond which the ice sheet would eventually be eliminated.

scholarly journals GrSMBMIP: Intercomparison of the modelled 1980-2012 surface mass balance over the Greenland Ice sheet

2020 ◽  
Author(s):  
Xavier Fettweis ◽  
Keyword(s):  
Mass Loss ◽  
Mass Balance ◽  
Climate Models ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Meltwater Runoff

<p>The Greenland Ice Sheet (GrIS) mass loss has been accelerating at a rate of about 20 +/- 10 Gt/yr<sup>2</sup> since the end of the 1990's, with around 60% of this mass loss directly attributed to enhanced surface meltwater runoff. However, in the climate and glaciology communities, different approaches exist on how to model the different surface mass balance (SMB) components using: (1) complex physically-based climate models which are computationally expensive; (2) intermediate complexity energy balance models; (3) simple and fast positive degree day models which base their inferences on statistical principles and are computationally highly efficient. Additionally, many of these models compute the SMB components based on different spatial and temporal resolutions, with different forcing fields as well as different ice sheet topographies and extents, making inter-comparison difficult. In the GrIS SMB model intercomparison project (GrSMBMIP) we address these issues by forcing each model with the same data (i.e., the ERA-Interim reanalysis) except for two global models for which this forcing is limited to the oceanic conditions, and at the same time by interpolating all modelled results onto a common ice sheet mask at 1 km horizontal resolution for the common period 1980-2012. The SMB outputs from 13 models are then compared over the GrIS to (1) SMB estimates using a combination of gravimetric remote sensing data from GRACE and measured ice discharge, (2) ice cores, snow pits, in-situ SMB observations, and (3) remotely sensed bare ice extent from MODerate-resolution Imaging Spectroradiometer (MODIS). Our results reveal that the mean GrIS SMB of all 13 models has been positive between 1980 and 2012 with an average of 340 +/- 112 Gt/yr, but has decreased at an average rate of -7.3 Gt/yr<sup>2</sup> (with a significance of 96%), mainly driven by an increase of 8.0 Gt/yr<sup>2</sup> (with a significance of 98%) in meltwater runoff. Spatially, the largest spread among models can be found around the margins of the ice sheet, highlighting the need for accurate representation of the GrIS ablation zone extent and processes driving the surface melt. In addition, a higher density of in-situ SMB observations is required, especially in the south-east accumulation zone, where the model spread can reach 2 mWE/yr due to large discrepancies in modelled snowfall accumulation. Overall, polar regional climate models (RCMs) perform the best compared to observations, in particular for simulating precipitation patterns. However, other simpler and faster models have biases of same order than RCMs with observations and remain then useful tools for long-term simulations. It is also interesting to note that the ensemble mean of the 13 models produces the best estimate of the present day SMB relative to observations, suggesting that biases are not systematic among models. Finally, results from MAR forced by ERA5 will be added in this intercomparison to evaluate the added value of using this new reanalysis as forcing vs the former ERA-Interim reanalysis (used in SMBMIP). </p>

scholarly journals The pattern of anthropogenic signal emergence in Greenland Ice Sheet surface mass balance

2014 ◽  
Vol 41 (16) ◽  
pp. 6002-6008 ◽  
Author(s):  
Jeremy G. Fyke ◽  
Miren Vizcaíno ◽  
William H. Lipscomb
Keyword(s):  
Mass Balance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Sheet Surface

scholarly journals Surface mass balance model intercomparison for the Greenland ice sheet

2012 ◽  
Vol 6 (5) ◽  
pp. 3999-4036 ◽  
Author(s):  
C. L. Vernon ◽  
J. L. Bamber ◽  
J. E. Box ◽  
M. R. van den Broeke ◽  
X. Fettweis ◽  
...  
Keyword(s):  
Mass Balance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Balance Model ◽  
Surface Mass Balance ◽  
Equilibrium Line Altitude ◽  
Surface Mass ◽  
Process Representation ◽  
Model Average

Abstract. Four simulations of the surface mass balance (SMB) of the Greenland ice sheet (GrIS) are compared over the period 1960–2008. 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 km2 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.

scholarly journals Greenland ice sheet surface mass-balance variability: 1991–2003

2005 ◽  
Vol 42 ◽  
pp. 90-94 ◽  
Author(s):  
J.E. Box
Keyword(s):  
Mass Balance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Atmospheric Model ◽  
Horizontal Resolution ◽  
Surface Mass Balance ◽  
Positive Trend ◽  
Surface Mass ◽  
Sheet Surface ◽  
Temperature And Precipitation

AbstractThe Polar MM5 mesoscale atmospheric model was run for 13 years (1991–2003) over Greenland at 24 km horizontal resolution (Box and others, 2004). The model physics were driven by satellite, station and weather-balloon observational data assimilation, i.e. European Centre for Medium-Range Weather Forecasts (ECMWF) operational analysis. The analysis in this study focuses on the response of the surface mass balance to its primary controls: temperature and precipitation. The results indicate coherent spatial patterns of variability and statistically significant links with temperature and precipitation and the North Atlantic Oscillation. Precipitation trends have the same spatial pattern and sign as temperature, suggesting an association of precipitation and temperature variability. Increasing temperatures contribute to an increasing ablation trend and expansion of the ablation zone despite increasing accumulation trends. The Pinatubo (Philippines) volcanic cooling in the early 1990s enhances this apparent warming trend. Only in the northeast does precipitation appear to dominate the surface mass balance, where both temperature and precipitation have decreased. There is little evidence for a total ice-sheet surface mass-balance trend, although the meltwater runoff has a positive trend and, combined with iceberg discharge and basal melting estimates, suggests the ice sheet as a whole is in a state of net mass loss over this period.

scholarly journals Future climate warming increases Greenland ice sheet surface mass balance variability

2014 ◽  
Vol 41 (2) ◽  
pp. 470-475 ◽  
Author(s):  
Jeremy G. Fyke ◽  
Miren Vizcaíno ◽  
William Lipscomb ◽  
Stephen Price
Keyword(s):  
Mass Balance ◽  
Climate Warming ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Future Climate ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Sheet Surface
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