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  • 1995-1999  (15)
Collection
Publisher
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Modelling the short-term response of the Greenland ice-sheet to global warming (1997)
    Springer
    Climate dynamics 13 (1997), S. 733-744 
    Details
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract.  A two-dimensional vertically integrated ice flow model has been developed to test the importance of various processes and concepts used for the prediction of the contribution of the Greenland ice-sheet to sea-level rise over the next 350 y (short-term response). The mass balance is modelled by the degree-day method and the energy-balance method. The lithosphere is considered to respond isostatically to a point load and the time evolution of the bedrock follows from a viscous asthenosphere. According to the IPCC-IS92a scenario (with constant aerosols after 1990) the Greenland ice-sheet is likely to cause a global sea level rise of 10.4 cm by 2100 AD. It is shown, however, that the result is sensitive to precise model formulations and that simplifications as used in the sea-level projection in the IPCC-96 report yield less accurate results. Our model results indicate that, on a time scale of a hundred years, including the dynamic response of the ice-sheet yields more mass loss than the fixed response in which changes in geometry are not incorporated. It appears to be important to consider sliding, as well as the fact that climate sensitivity increases for larger perturbations. Variations in predicted sea-level change on a time scale of hundred years depend mostly on the initial state of the ice-sheet. On a time scale of a few hundred years, however, the variability in the predicted melt is dominated by the variability in the climate scenarios.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003820050194
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Modelling the response of glaciers to climate warming (1998)
    Springer
    Climate dynamics 14 (1998), S. 267-274 
    Details
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract  Dynamic ice-flow models for 12 glaciers and ice caps have been forced with various climate change scenarios. The volume of this sample spans three orders of magnitude. Six climate scenarios were considered: from 1990 onwards linear warming rates of 0.01, 0.02 and 0.04 K a-1, with and without concurrent changes in precipitation. The models, calibrated against the historic record of glacier length where possible, were integrated until 2100. The differences in individual glacier responses are very large. No straightforward relationship between glacier size and fractional change of ice volume emerges for any given climate scenario. The hypsometry of individual glaciers and ice caps plays an important role in their response, thus making it difficult to generalize results. For a warming rate of 0.04 K a-1, without increase in precipitation, results indicate that few glaciers would survive until 2100. On the other hand, if the warming rate were to be limited to 0.01 K a-1 with an increase in precipitation of 10% per degree warming, we predict that overall loss would be restricted to 10 to 20% of the 1990 volume.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003820050222
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  • 3
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    Response of valley glaciers to climate change and kinematic waves: a study with a numerical ice-flow model (1995)
    Cambridge University Press
    Details
    Publication Date: 1995-01-01
    Description: A simple numerical flow model that couples mass divergence directly to basal shear stress as the only driving force is used to study kinematic waves. Kinematic waves that result from a perturbation of the ice thickness or mass balance are compared with the linear kinematic-wave theory of Nye/Weertman. The wave velocity is calculated as a function of the wavelength and amplitude of a perturbation. The modelled wave velocity is typically 6–8 times the vertically averaged velocity in the flow direction whereas linear theory predicts a factor of only 5.An experiment with the geometry of Hintereisferner, Austria, shows that the increase in the local ice velocity during a kinematic wave is about 10% but varies slightly depending on the position along the glacier and the amplitude of the kinematic wave. Kinematic waves are thus hard to detect from velocity measurements.The dynamics of simple continuity models are rich enough to support a variety of kinematic-wave phenomena. Such models are a useful tool to study the response of valley glaciers to climate change.
    Print ISSN: 0022-1430
    Electronic ISSN: 1727-5652
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
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  • 4
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    The importance of thermodynamics for modeling the volume of the Greenland Ice Sheet (1999)
    American Geophysical Union
    Details
    Publication Date: 1999-02-01
    Print ISSN: 0148-0227
    Electronic ISSN: 2156-2202
    Topics: Geosciences
    Published by American Geophysical Union
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  • 5
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    Processes of buildup and retreat of the Greenland Ice Sheet (1999)
    American Geophysical Union
    Details
    Publication Date: 1999-02-01
    Print ISSN: 0148-0227
    Electronic ISSN: 2156-2202
    Topics: Geosciences
    Published by American Geophysical Union
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  • 6
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    Projections of global mean sea level rise calculated with a 2D energy-balance climate model and dynamic ice sheet models (1997)
    Taylor & Francis
    Details
    Publication Date: 1997-08-01
    Print ISSN: 0280-6495
    Electronic ISSN: 1600-0870
    Topics: Geography , Geosciences , Physics
    Published by Taylor & Francis on behalf of Department of Meteorology (MISU), Stockholm University.
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  • 7
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    Response of valley glaciers to climate change and kinematic waves: a study with a numerical ice-flow model (1995)
    Cambridge University Press
    Details
    Publication Date: 1995-01-01
    Description: A simple numerical flow model that couples mass divergence directly to basal shear stress as the only driving force is used to study kinematic waves. Kinematic waves that result from a perturbation of the ice thickness or mass balance are compared with the linear kinematic-wave theory of Nye/Weertman. The wave velocity is calculated as a function of the wavelength and amplitude of a perturbation. The modelled wave velocity is typically 6–8 times the vertically averaged velocity in the flow direction whereas linear theory predicts a factor of only 5.An experiment with the geometry of Hintereisferner, Austria, shows that the increase in the local ice velocity during a kinematic wave is about 10% but varies slightly depending on the position along the glacier and the amplitude of the kinematic wave. Kinematic waves are thus hard to detect from velocity measurements.The dynamics of simple continuity models are rich enough to support a variety of kinematic-wave phenomena. Such models are a useful tool to study the response of valley glaciers to climate change.
    Print ISSN: 0022-1430
    Electronic ISSN: 1727-5652
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
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  • 8
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    Mass-balance modelling of the Greenland ice sheet: a comparison of an energy-balance and a degree-day model (1996)
    Cambridge University Press
    Details
    Publication Date: 1996-01-01
    Description: A degree-day model and an energy-balance model for the Greenland ice sheet are compared. The two models are compared at a grid with 20 km spacing. Input for both models is elevation, latitude and accumulation. The models calculate the annual ablation over the entire ice sheet. Although on the whole the two models yield similar results, depending on the tuning of the models, regional discrepancies of up to 45% occur, especially for northern Greenland. The performance of the two types of model is evaluated by comparing the model results with the sparsely available (long-term) mass-balance measurements. Results show that the energy-balance model tends to predict a more accurate mass-balance gradient with elevation than does the degree-day model.Since so little is known about the present-day climate of the ice sheet, it is more useful to consider the sensitivity of the ablation to various climate elements than to consider the actual present-day ablation. Results show that for a 1 K temperature perturbation, sea-level rise is 0.31 mm year−1 for the energy-balance model and 0.34 mm year−1 for the degree-day model. After tuning the degree-day model to a value of the ablation, equivalent to the ablation calculated by the energy-balance model, sensitivity of the degree-day model increases to 0.37 mm sea-level change per year. This means that the sensitivity of the degree-day model for a 1 K temperature perturbation is about 20% higher than the sensitivity of the energy-balance model. Another set of experiments shows that the sensitivity of the ablation is dependent on the magnitude of the temperature perturbation for the two models. Both models show an increasing sensitivity per degree for larger perturbations. The increase in the sensitivity is larger for the degree-day model than for the energy-balance model. The differences in the sensitivity are mainly concentrated in the southern parts of the ice sheet.Experiments for the Bellagio temperature scenario. 0.3°C increase in temperature per decade, leads to sea-level rise of 4.4 cm over a period of 100 years for the energy-balance model. The degree-day model predicts for the same forcing a 5.8 cm rise which is about 32% higher than the result of the energy-balance model.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
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  • 9
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    Mass-balance modelling of the Greenland ice sheet: a comparison of an energy-balance and a degree-day model (1996)
    Cambridge University Press
    Details
    Publication Date: 1996-01-01
    Description: A degree-day model and an energy-balance model for the Greenland ice sheet are compared. The two models are compared at a grid with 20 km spacing. Input for both models is elevation, latitude and accumulation. The models calculate the annual ablation over the entire ice sheet. Although on the whole the two models yield similar results, depending on the tuning of the models, regional discrepancies of up to 45% occur, especially for northern Greenland. The performance of the two types of model is evaluated by comparing the model results with the sparsely available (long-term) mass-balance measurements. Results show that the energy-balance model tends to predict a more accurate mass-balance gradient with elevation than does the degree-day model. Since so little is known about the present-day climate of the ice sheet, it is more useful to consider the sensitivity of the ablation to various climate elements than to consider the actual present-day ablation. Results show that for a 1 K temperature perturbation, sea-level rise is 0.31 mm year−1 for the energy-balance model and 0.34 mm year−1 for the degree-day model. After tuning the degree-day model to a value of the ablation, equivalent to the ablation calculated by the energy-balance model, sensitivity of the degree-day model increases to 0.37 mm sea-level change per year. This means that the sensitivity of the degree-day model for a 1 K temperature perturbation is about 20% higher than the sensitivity of the energy-balance model. Another set of experiments shows that the sensitivity of the ablation is dependent on the magnitude of the temperature perturbation for the two models. Both models show an increasing sensitivity per degree for larger perturbations. The increase in the sensitivity is larger for the degree-day model than for the energy-balance model. The differences in the sensitivity are mainly concentrated in the southern parts of the ice sheet. Experiments for the Bellagio temperature scenario. 0.3°C increase in temperature per decade, leads to sea-level rise of 4.4 cm over a period of 100 years for the energy-balance model. The degree-day model predicts for the same forcing a 5.8 cm rise which is about 32% higher than the result of the energy-balance model.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
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  • 10
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    On elevation models as input for mass-balance calculations of the Greenland ice sheet (1996)
    Cambridge University Press
    Details
    Publication Date: 1996-01-01
    Description: In this paper the elevation model for the Greenland ice sheet based upon radio-echo-sounding flights of the Technical University of Denmark (TUD) (Letréguilly and others, 1991) are compared with the satellite-altimetry model (Tscherning and others, 1993) improved with airborne-laser and radar altimetry (IA model). Although the general hypsometry of both data sets is rather similar, differences seem to be large at individual points along the ice margin. Over the entire ice sheet, the difference between the IA model and the TUD model is 33 m with a root-mean-square error of 112 m. Differential GPS measurements collected in the ice-marginal zone near Søndre Strømfjord show that the IA model is more accurate than the TUD model. The latter data set underestimates the elevation by approximately 150 m in the ice-marginal zone near Søndre Strømfjord. Calculation of the ablation with an energy-balance model and with a degree-day model points to a 20% decrease in the ablation if the IA model is used. Not only does this show the sensitivity of ablation calculations to the orographic input but it also indicates that the ablation calculated by the models used nowadays is relatively overestimated.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
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