scholarly journals Self-similarity in glacier surface characteristics

2003 ◽  
Vol 49 (167) ◽  
pp. 547-554 ◽  
Author(s):  
Neil S. Arnold ◽  
W. Gareth Rees
Keyword(s):  
Surface Roughness ◽  
Energy Balance ◽  
Spatial Variability ◽  
Snow Depth ◽  
Surface Albedo ◽  
Small Scale ◽  
Late Winter ◽  
Glacier Surface ◽  
Correlation Lengths ◽  
Aerodynamic Roughness

AbstractCatchment-wide information on glacier snow-cover depth, surface albedo and surface roughness is important input data for distributed models of glacier energy balance. In this study, we investigate the small-scale (mm to 100 m) spatial variability in these properties, with a view to better simulating this variability in such models. Data were collected on midre Lovénbreen, a 6 km2 valley glacier in northwest Svalbard. The spatial variability of all three properties was found to be self-similar over the range of scales under investigation. Snow depth and albedo exhibit a correlation length within which measurements were spatially autocorrelated. Late-winter and summer properties of snow depth differed, with smaller depths in summer due to melt, and shorter correlation lengths. Similar correlation lengths for snow depth and surface albedo may suggest that snow-depth variation is an important control on the small-scale spatial variability of glacier surface albedo. For surface roughness, the data highlight a possible problem in energy-balance studies which use microtopographic surveys to calculate aerodynamic roughness, in that the scale of the measurements made affects the calculated roughness value. This suggests that further investigations of the relationships between surface form and aerodynamic roughness of glacier surfaces are needed.

scholarly journals Debris-covered energy balance model for Imja-Lhotse Shar Glacier in the Everest region of Nepal

2015 ◽  
Vol 9 (3) ◽  
pp. 3503-3540 ◽  
Author(s):  
D. R. Rounce ◽  
D. J. Quincey ◽  
D. C. McKinney
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Surface Roughness ◽  
Energy Balance ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Energy Balance Model ◽  
Balance Model ◽  
Glacier Surface ◽  
Supraglacial Lakes

Abstract. Debris thickness plays an important role in regulating ablation rates on debris-covered glaciers as well as controlling the likely size and location of supraglacial lakes. Despite its importance, lack of knowledge about debris properties and associated energy fluxes prevents the robust inclusion of the effects of a debris layer into most glacier surface energy balance models. This study combines fieldwork with a debris-covered energy balance model to estimate debris temperatures and ablation rates on Imja-Lhotse Shar glacier located in the Everest region of Nepal. The debris properties that significantly influence the energy balance model are thermal conductivity, albedo, and surface roughness. Fieldwork was conducted to measure thermal conductivity and a method was developed using Structure from Motion to estimate surface roughness. Debris temperatures measured during the 2014 melt season were used to calibrate and validate a debris-covered energy balance model by optimizing the albedo, thermal conductivity, and surface roughness at 10 debris-covered sites. Furthermore, three methods for estimating the latent heat flux were investigated. Model calibration and validation found the three methods had similar performance; however, comparison of modeled and measured ablation rates revealed that assuming a zero latent heat flux may overestimate ablation. Results also suggest that where debris moisture is unknown, measurements of the relative humidity or precipitation may be used to estimate wet debris periods, i.e., the latent heat flux is non-zero. The effect of temporal resolution on the model was also assessed and results showed that both 6 h data and daily average data slightly underestimate debris temperatures and ablation rates, thus these should only be used to estimate rough ablation rates when no other data are available.

scholarly journals Surface Energy Balance Sensitivity to Meteorological Variability on Haig Glacier, Canadian Rocky Mountains

2016 ◽  
Author(s):  
S. Ebrahimi ◽  
S. J. Marshall
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Rocky Mountains ◽  
Surface Albedo ◽  
Surface Energy Balance ◽  
Specific Humidity ◽  
Shortwave Radiation ◽  
Interannual Variations ◽  
Canadian Rocky Mountains ◽  
Glacier Surface

Abstract. Energy exchanges between the atmosphere and the glacier surface control the net energy available for snow and ice melt. Meteorological and glaciological observations are not always available to measure glacier energy and mass balance directly, so models of energy balance processes are often necessary to understand glacier response to meteorological variability and climate change. This paper explores the theoretical and empirical response of a mid-latitude glacier in the Canadian Rocky Mountains to the daily and interannual variations in the meteorological parameters that govern the surface energy balance. The model's reference conditions are based on 11 years of in situ observations from an automatic weather station at an elevation of 2660 m, in the upper ablation area of Haig Glacier. We use an energy balance model to run sensitivity tests to perturbations in temperature, specific humidity, wind speed, incoming shortwave radiation, and glacier surface albedo. The variables were perturbed one at a time for the duration of the glacier melt season, May to September, for the years 2002–2012. The experiments indicate that summer melt has the strongest sensitivity to interannual variations in incoming shortwave radiation, albedo, and temperature, in that order. To explore more realistic scenarios where meteorological variables and internal feedbacks such as the surface albedo co-evolve, we use the same perturbation approach using meteorological forcing from the North American Regional Reanalysis (NARR) over the period 1979–2014. These experiments provide an estimate of historical variability in Haig Glacier surface energy balance an d melt for years prior to our observational study. The methods introduced in this paper provide a methodology that can be employed in distributed energy balance modelling at regional scales. They also provide the foundation for theoretical framework that can be adapted to compare the climatic sensitivity of glaciers in different climate regimes, e.g., polar, maritime, or tropical environments.

scholarly journals Using 3D turbulence-resolving simulations to understand the impact of surface properties on the energy balance of a debris-covered glacier

2020 ◽  
Vol 14 (5) ◽  
pp. 1611-1632
Author(s):  
Pleun N. J. Bonekamp ◽  
Chiel C. van Heerwaarden ◽  
Jakob F. Steiner ◽  
Walter W. Immerzeel
Keyword(s):  
Energy Balance ◽  
Surface Properties ◽  
Turbulent Fluxes ◽  
Specific Humidity ◽  
Small Scale ◽  
High Mountain ◽  
Conductive Heat ◽  
Glacier Surface ◽  
Glacier Melt ◽  
The Impact

Abstract. Debris-covered glaciers account for almost one-fifth of the total glacier ice volume in High Mountain Asia; however, their contribution to the total glacier melt remains uncertain, and the drivers controlling this melt are still largely unknown. Debris influences the properties (e.g. albedo, thermal conductivity, roughness) of the glacier surface and thus the surface energy balance and glacier melt. In this study we have used sensitivity tests to assess the effect of surface properties of debris on the spatial distribution of micrometeorological variables such as wind fields, moisture and temperature. Subsequently we investigated how those surface properties drive the turbulent fluxes and eventually the conductive heat flux of a debris-covered glacier. We simulated a debris-covered glacier (Lirung Glacier, Nepal) at a 1 m resolution with the MicroHH model, with boundary conditions retrieved from an automatic weather station (temperature, wind and specific humidity) and unmanned aerial vehicle flights (digital elevation map and surface temperature). The model was validated using eddy covariance data. A sensitivity analysis was then performed to provide insight into how heterogeneous surface variables control the glacier microclimate. Additionally, we show that ice cliffs are local melt hot spots and that turbulent fluxes and local heat advection amplify spatial heterogeneity on the surface. The high spatial variability of small-scale meteorological variables suggests that point-based station observations cannot be simply extrapolated to an entire glacier. These outcomes should be considered in future studies for a better estimation of glacier melt in High Mountain Asia.

scholarly journals A scale-dependent model to represent changing aerodynamic roughness of ablating glacier ice based on repeat topographic surveys

2020 ◽  
Vol 66 (260) ◽  
pp. 950-964
Author(s):  
Thomas Smith ◽  
Mark W. Smith ◽  
Joshua R. Chambers ◽  
Rudolf Sailer ◽  
Lindsey Nicholson ◽  
...  
Keyword(s):  
Energy Balance ◽  
Laser Scanning ◽  
Glacier Surface ◽  
Mountain Glacier ◽  
Ice Surface ◽  
Glacier Ice ◽  
Consistent Increase ◽  
Aerodynamic Roughness ◽  
Surface Ice ◽  
Time Substitution

AbstractTurbulent fluxes make a substantial and growing contribution to the energy balance of ice surfaces globally, but are poorly constrained owing to challenges in estimating the aerodynamic roughness length (z0). Here, we used structure from motion (SfM) photogrammetry and terrestrial laser scanning (TLS) surveys to make plot-scale 2-D and 3-D microtopographic estimations of z0 and upscale these to map z0 across an ablating mountain glacier. At plot scales, we found spatial variability in z0 estimates of over two orders of magnitude with unpredictable z0 trajectories, even when classified into ice surface types. TLS-derived surface roughness exhibited strong relationships with plot-scale SfM z0 estimates. At the glacier scale, a consistent increase in z0 of ~0.1 mm d−1 was observed. Space-for-time substitution based on time since surface ice was exposed by snow melt confirmed this gradual increase in z0 over 60 d. These measurements permit us to propose a scale-dependent temporal z0 evolution model where unpredictable variability at the plot scale gives way to more predictable changes of z0 at the glacier scale. This model provides a critical step towards deriving spatially and temporally distributed representations of z0 that are currently lacking in the parameterisation of distributed glacier surface energy balance models.

scholarly journals Effects of surface roughness and light-absorbing impurities on glacier surface albedo, August-one ice cap, Qilian Mountains, China

2020 ◽  
Author(s):  
Junfeng Liu ◽  
Rensheng Chen ◽  
Yongjian Ding ◽  
Chuntan Han ◽  
Yong Yang ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Large Scale ◽  
Surface Albedo ◽  
Flow Line ◽  
Glacier Surface ◽  
Negative Power ◽  
Mountain Glaciers ◽  
Ice Cap ◽  
Ice Surface ◽  
Exciting Potential

Abstract. Surface albedo is the main influence on surface melt for Qilian mountain glaciers. Fluctuations in surface albedo are due primarily to variations in micro scale surface roughness (ξ) and light-absorbing impurities (LAIs) in this region. However, combined ξ and LAIs effects over glacier surface albedo are rarely studied and surface roughness rarely considered in the albedo parameterization methods in this region. The present study was conducted in tandem with an intensive photogrammetric survey of glacier surface roughness, LAIs samples and albedo observations along the main flow-line of August-one ice cap during the 2018 melt season. Automatic photogrammetry of surface roughness and automatic observation of glacier surface albedo was conducted at middle of the ice cap in 2018. Detailed analysis indicates a negative power function and positive linear relationship exist between ξ and albedo for snow and ice surface, respectively. ξ could explain 68% of snow surface albedo and 38 % of ice surface albedo variation in melt season. Effective LAIs concentration (Cξ) calculated by consider ξ effect over LAIs deposition account for more than 63 % of albedo variation at ice surface. Using either ξ or Cξ to estimate ice surface albedo would be a great improvement over some current parameterization methods, such as assuming a constant mean ice surface albedo. A finer resolution of above 50 mm and above 100 mm is recommended for ice and snow ξ calculations, which explain more albedo variation than coarse resolutions below it. With advances in topographic surveys to improve the resolution, extent and availability of topographic datasets and surface roughness, appropriate parameterizations of albedo based on ξ have exciting potential to be applied over large scale snow cover and glacier.

scholarly journals Debris-covered glacier energy balance model for Imja–Lhotse Shar Glacier in the Everest region of Nepal

2015 ◽  
Vol 9 (6) ◽  
pp. 2295-2310 ◽  
Author(s):  
D. R. Rounce ◽  
D. J. Quincey ◽  
D. C. McKinney
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Surface Roughness ◽  
Energy Balance ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Energy Balance Model ◽  
Balance Model ◽  
Glacier Surface ◽  
Supraglacial Lakes

Abstract. Debris thickness plays an important role in regulating ablation rates on debris-covered glaciers as well as controlling the likely size and location of supraglacial lakes. Despite its importance, lack of knowledge about debris properties and associated energy fluxes prevents the robust inclusion of the effects of a debris layer into most glacier surface energy balance models. This study combines fieldwork with a debris-covered glacier energy balance model to estimate debris temperatures and ablation rates on Imja–Lhotse Shar Glacier located in the Everest region of Nepal. The debris properties that significantly influence the energy balance model are the thermal conductivity, albedo, and surface roughness. Fieldwork was conducted to measure thermal conductivity and a method was developed using Structure from Motion to estimate surface roughness. Debris temperatures measured during the 2014 melt season were used to calibrate and validate a debris-covered glacier energy balance model by optimizing the albedo, thermal conductivity, and surface roughness at 10 debris-covered sites. Furthermore, three methods for estimating the latent heat flux were investigated. Model calibration and validation found the three methods had similar performance; however, comparison of modeled and measured ablation rates revealed that assuming the latent heat flux is zero may overestimate ablation. Results also suggest that where debris moisture is unknown, measurements of the relative humidity or precipitation may be used to estimate wet debris periods, i.e., when the latent heat flux is non-zero. The effect of temporal resolution on the model was also assessed and results showed that both 6 h data and daily average data slightly underestimate debris temperatures and ablation rates; thus these should only be used to estimate rough ablation rates when no other data are available.

scholarly journals Spatial distribution of surface ablation in the terminus of Rhonegletscher, Switzerland

2011 ◽  
Vol 52 (58) ◽  
pp. 1-8 ◽  
Author(s):  
Shin Sugiyama ◽  
Takeshi Yoshizawa ◽  
Matthias Huss ◽  
Shun Tsutaki ◽  
Daisuke Nishimura
Keyword(s):  
Field Data ◽  
Surface Albedo ◽  
Surface Energy Balance ◽  
Accurate Estimation ◽  
Small Scale ◽  
Glacier Surface ◽  
Local Conditions ◽  
Temperature Index ◽  
Rate Distribution ◽  
Ice Surface

AbstarctThe spatial pattern of glacier surface melt was measured with a resolution of 20–100m within a region extending 1 km up-glacier from the terminus of Rhonegletscher, Switzerland. The melt rate was monitored from 6 July to 6 September 2009 using 44 ablation stakes. We also measured the surface albedo near the stakes to investigate the importance of this parameter for the melt-rate distribution. The melt rate varied from 32.8 to 71.9 mm w.e. d–1 in the study area. Our measurements suggest that the spatial variation of the melt rate can be explained by (1) shading of the ice surface by neighbouring mountains, (2) surface albedo and (3) effects of microclimate (e.g. radiation from sidewalls) on the surface energy balance. The observed melt-rate distribution was compared to the results of a temperature-index melt model, which takes into account shading of direct solar illumination but not the other two effects. The model reproduces some important features of the field data, but its spatial variations are generally less than the measured values. Our study shows the importance of albedo and other local conditions in the accurate estimation of the small-scale melt-rate distribution.

scholarly journals The surface energy balance of Austre Lovénbreen, Svalbard, during the ablation period in 2014

2021 ◽  
Vol 40 ◽  
Author(s):  
Xiaowei Zou ◽  
Minghu Ding ◽  
Weijun Sun ◽  
Diyi Yang ◽  
Weigang Liu ◽  
...  
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Surface Albedo ◽  
Surface Energy Balance ◽  
Meteorological Data ◽  
Longwave Radiation ◽  
Heat Sinks ◽  
Shortwave Radiation ◽  
Balance Model ◽  
Glacier Surface

The ability to simulate the surface energy balance is key to studying land–atmosphere interactions; however, it remains a weakness in Arctic polar sciences. Based on the analysis of meteorological data from 1 June to 30 September 2014 from an automatic weather station on the glacier Austre Lovénbreen, near Ny–Ålesund, Svalbard, we established a surface energy balance model to simulate surface melt. The results reveal that the net shortwave radiation accounts for 87% (39 W m–2) of the energy sources, and is controlled by cloud cover and surface albedo. The sensible heat equals 6 W m–2 and is a continuous energy source at the glacier surface. Net longwave radiation and latent heat account for 31% and 5% of heat sinks, respectively. The simulated summer mass balance equals –793 mm w.e., agreeing well with the observation by an ultrasonic ranger.

scholarly journals Retreating alpine glaciers: increased melt rates due to accumulation of dust (Vadret da Morteratsch, Switzerland)

2009 ◽  
Vol 55 (192) ◽  
pp. 729-736 ◽  
Author(s):  
J. Oerlemans ◽  
R.H. Giesen ◽  
M.R. Van Den Broeke
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Surface Albedo ◽  
Feedback Mechanism ◽  
Surface Energy Budget ◽  
Balance Model ◽  
Weather Station ◽  
Automatic Weather Station ◽  
Ablation Zone ◽  
Glacier Surface

AbstractThe automatic weather station (AWS) on the snout of the Vadret da Morteratsch, Switzerland, has delivered a unique 12 year meteorological dataset from the ablation zone of a temperate glacier. This dataset can be used to study multi-annual trends in the character of the surface energy budget. Since 2003 there has been a substantial darkening of the glacier tongue due to the accumulation of mineral and biogenic dust. The typical surface albedo in summer has dropped from 0.32 to 0.15. We have analysed the implications of the lowered albedo for the energy balance and the annual ablation. For the 4 year period 2003–06, the decreased albedo caused an additional removal of about 3.5 m of ice. Calculations with an energy-balance model show that the same increase in ablation is obtained by keeping the ice albedo fixed to 0.32 and increasing the air temperature by 1.7 K. Our analysis confirms that for retreating glaciers the deposition of dust from exposed side moraines on the glacier surface constitutes an important feedback mechanism. The mineral dust stimulates the growth of algae, lowers the surface albedo, enhances the melt rates, and thereby facilitates the further retreat of the glacier snout.

scholarly journals Application of an improved surface energy balance model to two large valley glaciers in the St. Elias Mountains, Yukon

2020 ◽  
pp. 1-16
Author(s):  
Tim Hill ◽  
Christine F. Dow ◽  
Eleanor A. Bash ◽  
Luke Copland
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Surface Energy Balance ◽  
Shortwave Radiation ◽  
Balance Model ◽  
Landsat 8 ◽  
Glacier Surface ◽  
Ice Dynamics ◽  
Surface Melt

Abstract Glacier surficial melt rates are commonly modelled using surface energy balance (SEB) models, with outputs applied to extend point-based mass-balance measurements to regional scales, assess water resource availability, examine supraglacial hydrology and to investigate the relationship between surface melt and ice dynamics. We present an improved SEB model that addresses the primary limitations of existing models by: (1) deriving high-resolution (30 m) surface albedo from Landsat 8 imagery, (2) calculating shadows cast onto the glacier surface by high-relief topography to model incident shortwave radiation, (3) developing an algorithm to map debris sufficiently thick to insulate the glacier surface and (4) presenting a formulation of the SEB model coupled to a subsurface heat conduction model. We drive the model with 6 years of in situ meteorological data from Kaskawulsh Glacier and Nàłùdäy (Lowell) Glacier in the St. Elias Mountains, Yukon, Canada, and validate outputs against in situ measurements. Modelled seasonal melt agrees with observations within 9% across a range of elevations on both glaciers in years with high-quality in situ observations. We recommend applying the model to investigate the impacts of surface melt for individual glaciers when sufficient input data are available.

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