scholarly journals Response of the Energy Balance on the Margin of the Greenland Ice Sheet to Temperature Changes

1990 ◽  
Vol 36 (123) ◽  
pp. 217-221 ◽  
Author(s):  
Roger J. Braithwaite ◽  
Ole B. Olesen
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Air Temperature ◽  
Sensible Heat Flux ◽  
Ice Sheet ◽  
Temperature Response ◽  
Greenland Ice Sheet ◽  
Energy Balance Model ◽  
Balance Model ◽  
Sensible Heat

AbstractDaily ice ablation on two outlet glaciers from the Greenland ice sheet, Nordbogletscher (1979–83) and Qamanârssûp sermia (1980–86), is related to air temperature by a linear regression equation. Analysis of this ablation-temperature equation with the help of a simple energy-balance model shows that sensible-heat flux has the greatest temperature response and accounts for about one-half of the temperature response of ablation. Net radiation accounts for about one-quarter of the temperature response of ablation, and latent-heat flux and errors account for the remainder. The temperature response of sensible-heat flux at QQamanârssûp sermia is greater than at Nordbogletscher mainly due to higher average wind speeds. The association of high winds with high temperatures during Föhn events further increases sensible-heat flux. The energy-balance model shows that ablation from a snow surface is only about half that from an ice surface at the same air temperature.

scholarly journals Response of the Energy Balance on the Margin of the Greenland Ice Sheet to Temperature Changes

1990 ◽  
Vol 36 (123) ◽  
pp. 217-221 ◽  
Author(s):  
Roger J. Braithwaite ◽  
Ole B. Olesen
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Air Temperature ◽  
Sensible Heat Flux ◽  
Ice Sheet ◽  
Temperature Response ◽  
Greenland Ice Sheet ◽  
Energy Balance Model ◽  
Balance Model ◽  
Sensible Heat

AbstractDaily ice ablation on two outlet glaciers from the Greenland ice sheet, Nordbogletscher (1979–83) and Qamanârssûp sermia (1980–86), is related to air temperature by a linear regression equation. Analysis of this ablation-temperature equation with the help of a simple energy-balance model shows that sensible-heat flux has the greatest temperature response and accounts for about one-half of the temperature response of ablation. Net radiation accounts for about one-quarter of the temperature response of ablation, and latent-heat flux and errors account for the remainder. The temperature response of sensible-heat flux at QQamanârssûp sermia is greater than at Nordbogletscher mainly due to higher average wind speeds. The association of high winds with high temperatures during Föhn events further increases sensible-heat flux. The energy-balance model shows that ablation from a snow surface is only about half that from an ice surface at the same air temperature.

scholarly journals Evaluation of a Two-Source Snow–Vegetation Energy Balance Model for Estimating Surface Energy Fluxes in a Rangeland Ecosystem

2014 ◽  
Vol 15 (1) ◽  
pp. 143-158 ◽  
Author(s):  
Cezar Kongoli ◽  
William P. Kustas ◽  
Martha C. Anderson ◽  
John M. Norman ◽  
Joseph G. Alfieri ◽  
...  
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Surface Energy ◽  
Snow Cover ◽  
Sensible Heat Flux ◽  
Energy Balance Model ◽  
Balance Model ◽  
Sensible Heat ◽  
Energy Fluxes ◽  
Surface Energy Fluxes

Abstract The utility of a snow–vegetation energy balance model for estimating surface energy fluxes is evaluated with field measurements at two sites in a rangeland ecosystem in southwestern Idaho during the winter of 2007: one site dominated by aspen vegetation and the other by sagebrush. Model parameterizations are adopted from the two-source energy balance (TSEB) modeling scheme, which estimates fluxes from the vegetation and surface substrate separately using remotely sensed measurements of land surface temperature. Modifications include development of routines to account for surface snowmelt energy flux and snow masking of vegetation. Comparisons between modeled and measured surface energy fluxes of net radiation and turbulent heat showed reasonable agreement when considering measurement uncertainties in snow environments and the simplified algorithm used for the snow surface heat flux, particularly on a daily basis. There was generally better performance over the aspen field site, likely due to more reliable input data of snow depth/snow cover. The model was robust in capturing the evolution of surface energy fluxes during melt periods. The model behavior was also consistent with previous studies that indicate the occurrence of upward sensible heat fluxes during daytime owing to solar heating of vegetation limbs and branches, which often exceeds the downward sensible heat flux driving the snowmelt. However, model simulations over aspen trees showed that the upward sensible heat flux could be reversed for a lower canopy fraction owing to the dominance of downward sensible heat flux over snow. This indicates that reliable vegetation or snow cover fraction inputs to the model are needed for estimating fluxes over snow-covered landscapes.

scholarly journals A Simple Energy-Balance Model to Calculate Ice Ablation at the Margin of the Greenland Ice Sheet

1990 ◽  
Vol 36 (123) ◽  
pp. 222-228 ◽  
Author(s):  
Roger J. Braithwaite ◽  
Ole Β. Olesen
Keyword(s):  
Energy Balance ◽  
Sensible Heat Flux ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ablation Rate ◽  
Short Wave ◽  
Energy Balance Model ◽  
Balance Model ◽  
Wave Radiation ◽  
Climate Data

AbstractData for daily ice ablation on two outlets from the Greenland ice sheet, Nordbogletscher (1979–83) and Qamanârssûp sermia (1980–86), are used to test a simple energy-balance model which calculates ablation from climate data. The mean errors of the model are only −1.1 and −1.3 mm water d−1 for Nordbogletscher (14 months) and Qamanârssûp sermia (21 months), respectively, with standard deviations of ±13.6 and ±18.9 mm water d−1 for calculating daily ablation. The larger error for Qamanârssûp sermia may be due to variations in ice albedo but the model also underestimates ablation during Föhn events.According to the model, radiation accounts for about two-thirds of mean ablation for June-August at the two sites, while turbulent fluxes account for about one-third. The average ablation rate is higher at Qamanârssûp sermia than at Nordbogletscher because both sensible-heat flux and short-wave radiation are higher.

scholarly journals A Simple Energy-Balance Model to Calculate Ice Ablation at the Margin of the Greenland Ice Sheet

1990 ◽  
Vol 36 (123) ◽  
pp. 222-228 ◽  
Author(s):  
Roger J. Braithwaite ◽  
Ole Β. Olesen
Keyword(s):  
Energy Balance ◽  
Sensible Heat Flux ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ablation Rate ◽  
Short Wave ◽  
Energy Balance Model ◽  
Balance Model ◽  
Wave Radiation ◽  
Climate Data

AbstractData for daily ice ablation on two outlets from the Greenland ice sheet, Nordbogletscher (1979–83) and Qamanârssûp sermia (1980–86), are used to test a simple energy-balance model which calculates ablation from climate data. The mean errors of the model are only −1.1 and −1.3 mm water d−1for Nordbogletscher (14 months) and Qamanârssûp sermia (21 months), respectively, with standard deviations of ±13.6 and ±18.9 mm water d−1for calculating daily ablation. The larger error for Qamanârssûp sermia may be due to variations in ice albedo but the model also underestimates ablation during Föhn events.According to the model, radiation accounts for about two-thirds of mean ablation for June-August at the two sites, while turbulent fluxes account for about one-third. The average ablation rate is higher at Qamanârssûp sermia than at Nordbogletscher because both sensible-heat flux and short-wave radiation are higher.

scholarly journals Energy Balance Calculations for the Ablation Period 1982 at Vernagtferner. Oetztal Alps

1985 ◽  
Vol 6 ◽  
pp. 158-160 ◽  
Author(s):  
Heidi Escher-Vetter
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Air Temperature ◽  
Sensible Heat Flux ◽  
Longwave Radiation ◽  
Radiation Balance ◽  
Sensible Heat ◽  
The Individual ◽  
The Relationship ◽  
Climatic Pattern

In this paper, some features of energy balance terms will be discussed in respect to the melting capacity available at the surface of Vernagtferner in the Oetztal Alps. The climatic pattern of summer 1982 is described, then the method of calculating individual terms (shortwave and longwave radiation balance, sensible and latent heat flux) from records of radiation, air temperature, humidity and wind. The results of these calculations are discussed for ice, firn and snow areas of the glacier. In particular the relationship between the four terms is shown for 15 July 1982, the day with highest meltwater production in 1982. These values are then compared with the maximum values of the individual terms, showing that the highest meltwater production is caused by the combination of quite high values of the individual terms, but not of the absolutely highest ones. The importance of sensible heat flux for meltwater production in 1982 is discussed: comparison between meltwater production for the whole summer and measured runoff shows reasonable accordance.

scholarly journals Increased Ablation at the Margin of the Greenland Ice Sheet under a Greenhouse-Effect Climate

1990 ◽  
Vol 14 ◽  
pp. 20-22 ◽  
Author(s):  
Roger J. Braithwaite ◽  
Ole B. Olesen
Keyword(s):  
Energy Balance ◽  
Greenhouse Effect ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ablation Rate ◽  
Summer Temperature ◽  
Energy Balance Model ◽  
Balance Model ◽  
Climatic Warming ◽  
West Greenland

Increased ablation under a greenhouse-effect climate is calculated by an energy-balance model for two sites at the margin of the Greenland ice sheet: Nordbogletscher, south Greenland, and Qamanârssûp sermia, West Greenland. The change in summer ablation is nearly linear with change in summer temperature, with gradients of 0.43 and 0.57 m water a−1 deg−1 for Nordbogletscher and Qamanârssûp sermia, respectively. However, the increase in ablation rate must be less in the higher parts of the ice sheet. A future climatic warming will therefore cause a rapid retreat of the ice-sheet margin and a steeper ice-sheet profile.

scholarly journals Backwasting rate on debris-covered Koxkar glacier, Tuomuer mountain, China

2010 ◽  
Vol 56 (196) ◽  
pp. 287-296 ◽  
Author(s):  
Haidong Han ◽  
Jian Wang ◽  
Junfeng Wei ◽  
Shiyin Liu
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Slope Angle ◽  
Sensible Heat Flux ◽  
Energy Balance Model ◽  
Total Heat ◽  
Balance Model ◽  
Covered Area ◽  
Koxkar Glacier ◽  
Mean Square Errors

AbstractA physically based energy-balance model with improved parameterization of solar radiation for a sloped ice surface has been developed to estimate the backwasting rate of an ice cliff in a debris-covered area. The model has been tested against observations between 5 August and 5 September 2008 on 38 ice cliffs in the debris-covered area of Koxkar glacier, Tuomuer mountain, China. We calculated that the energy-balance model gave a good estimate of the backwasting rates, with errors in the range ±1.96 cm d−1 and root-mean-square errors of 0.99 cm d−1. Errors arising from setting of surface albedo and turbulent flux parameterization were limited. We found that shortwave radiation is the most important heat source for ice-cliff ablation, contributing about 76% of the total heat available for ice melt, while the sensible heat flux provides nearly 24% of the total heat for ice-cliff wastage. The latent heat flux and net longwave radiation are comparatively small according to the model calculation. The mean backwasting rate of ice cliffs in the debris-covered area of Koxkar glacier is estimated at 7.64 m a−1 when the winter ablation is neglected. With this annual backwasting rate and given a mean slope angle of 46.4°, the backwasting of ice cliffs produces about 1.60 × 106 m3 of meltwater, accounting for about 7.3% of the total melt runoff from the debris-covered area.

scholarly journals Increased Ablation at the Margin of the Greenland Ice Sheet under a Greenhouse-Effect Climate

1990 ◽  
Vol 14 ◽  
pp. 20-22 ◽  
Author(s):  
Roger J. Braithwaite ◽  
Ole B. Olesen
Keyword(s):  
Energy Balance ◽  
Greenhouse Effect ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ablation Rate ◽  
Summer Temperature ◽  
Energy Balance Model ◽  
Balance Model ◽  
Climatic Warming ◽  
West Greenland

Increased ablation under a greenhouse-effect climate is calculated by an energy-balance model for two sites at the margin of the Greenland ice sheet: Nordbogletscher, south Greenland, and Qamanârssûp sermia, West Greenland. The change in summer ablation is nearly linear with change in summer temperature, with gradients of 0.43 and 0.57 m water a−1 deg−1 for Nordbogletscher and Qamanârssûp sermia, respectively. However, the increase in ablation rate must be less in the higher parts of the ice sheet. A future climatic warming will therefore cause a rapid retreat of the ice-sheet margin and a steeper ice-sheet profile.

scholarly journals Mass-balance modelling of the Greenland ice sheet: a comparison of an energy-balance and a degree-day model

1996 ◽  
Vol 23 ◽  
pp. 36-45 ◽  
Author(s):  
R. S. W. van de Wal
Keyword(s):  
Energy Balance ◽  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Energy Balance Model ◽  
Balance Model ◽  
Temperature Perturbation ◽  
Degree Day

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.

scholarly journals The secret life of ice sails

2017 ◽  
Vol 63 (242) ◽  
pp. 1049-1062 ◽  
Author(s):  
GEOFFREY W. EVATT ◽  
CHRISTOPH MAYER ◽  
AMY MALLINSON ◽  
I. DAVID ABRAHAMS ◽  
MATTHIAS HEIL ◽  
...  
Keyword(s):  
Heat Flux ◽  
Sensitivity Analysis ◽  
Steady State ◽  
Energy Balance ◽  
Surface Energy ◽  
Surface Energy Balance ◽  
Sensible Heat Flux ◽  
Balance Model ◽  
Sensible Heat ◽  
Glacier Surface

ABSTRACTWe present the first dedicated study into the phenomenon of ice sails. These are clean ice structures that protrude from the surface of a small number of debris-covered glaciers and can grow to heights of over 25 m. We draw together what is known about them from the academic/exploration literature and then analyse imagery. We show here that ice sails can develop by one of two mechanisms, both of which require clean ice to become surrounded by debris-covered ice, where the debris layer is shallow enough for the ice beneath it to melt faster than the clean ice. Once formed, ice sails can persist for decades, in an apparently steady state, before debris layer thickening eventually causes a reversal in the relative melt rates and the ice sails decay to merge back with the surrounding glacier surface. We support our image-based analysis with a surface energy-balance model and show that it compares well with available observations from Baltoro Glacier in the Karakoram. A sensitivity analysis of the model is performed and confirms the results from our empirical study that ice sails require a relatively high evaporative heat flux and/or a relatively low sensible heat flux in order to exist.

Sign in / Sign up

Export Citation Format

Share Document