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 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 Correcting for Systematic Underestimation of Topographic Glacier Aerodynamic Roughness Values From Hintereisferner, Austria

2021 ◽  
Vol 9 ◽  
Author(s):  
Joshua R. Chambers ◽  
Mark W. Smith ◽  
Thomas Smith ◽  
Rudolf Sailer ◽  
Duncan J. Quincey ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Regional Scale ◽  
Laser Scanner ◽  
Turbulent Energy ◽  
Temporal Variations ◽  
Glacier Surface ◽  
Order Of Magnitude ◽  
Spatio Temporal ◽  
Aerodynamic Roughness ◽  
Elevation Model

Spatially-distributed values of glacier aerodynamic roughness (z0) are vital for robust estimates of turbulent energy fluxes and ice and snow melt. Microtopographic data allow rapid estimates of z0 over discrete plot-scale areas, but are sensitive to data scale and resolution. Here, we use an extensive multi-scale dataset from Hintereisferner, Austria, to develop a correction factor to derive z0 values from coarse resolution (up to 30 m) topographic data that are more commonly available over larger areas. Resulting z0 estimates are within an order of magnitude of previously validated, plot-scale estimates and aerodynamic values. The method is developed and tested using plot-scale microtopography data generated by structure from motion photogrammetry combined with glacier-scale data acquired by a permanent in-situ terrestrial laser scanner. Finally, we demonstrate the application of the method to a regional-scale digital elevation model acquired by airborne laser scanning. Our workflow opens up the possibility of including spatio-temporal variations of z0 within glacier surface energy balance models without the need for extensive additional field data collection.

Global differences in the energy balance and melt rates of debris-covered glacier surfaces

2021 ◽  
Author(s):  
Evan Miles ◽  
Jakob Steiner ◽  
Pascal Buri ◽  
Walter Immerzeel ◽  
Francesca Pellicciotti
Keyword(s):  
Energy Balance ◽  
Wind Speed ◽  
Surface Energy ◽  
Mass Loss ◽  
Energy Absorption ◽  
Random Sets ◽  
Physical Parameters ◽  
High Mountain ◽  
Glacier Surface ◽  
Mountain Glacier

<p>Supraglacial debris covers 4% of mountain glacier area globally and generally reduces glacier surface melt. Studies have identified enhanced energy absorption at ice cliffs and supraglacial ponds scattered across the debris surface. Although these features generally cover a small portion of glacier surface area (5-10%) they contribute disproportionately to mass loss at the local glacier scales (20-40%). While past studies have identified their melt-enhancing role in High Mountain Asia, Alaska, and the Alps, it is not clear to what degree they enhance mass loss in other areas of the globe.</p><p>We model the surface energy balance for debris-covered ice, ice cliffs, and supraglacial ponds using meteorological records (4 radiative fluxes, wind speed, air temperature, humidity) from a set of on-glacier automated weather stations representing the global prevalence of debris covered glaciers. We generate 5000 random sets of values for physical parameters using probability distributions derived from literature. We also model the hypothetical energy balance of a debris-free glacier surface at each site, which we use to investigate the melt rates of distinct surface types relative to that of a clean ice glacier. This approach allows us to isolate the melt responses of debris, cliffs and ponds to the site specific meteorological forcing.</p><p>For each site we determine an Østrem curve for sub-debris melt as a function of debris thickness and a probabilistic understanding of surface energy absorption for ice cliffs, supraglacial ponds, and debris-covered ice. While debris leads to strong reductions in melt at all sites, we find an order-of-magnitude spread in sub-debris melt rates due solely to climatic differences between sites. The melt enhancement of ice cliffs relative to debris-covered ice is starkly apparent at all sites, and ice cliffs melt rates are generally 1.5-2.5 times the ablation rate for a clean ice surface. The supraglacial pond energy balance varies regionally, and is sensitive to wind speed and relative humidity, leading to energy absorption 0.4-1.2 times that of clean ice, but 5-10 times higher than debris-covered ice. Our results support the few past assessments of melt rates for cliffs and ponds, and indicate sub-regional coherence in the energy balance response of these features to climate.</p>

scholarly journals On the Relation of Net Balance, Ice Flow, and Surface Lowering of Lewis Glacier, Mount Kenya, East Africa, 1982–86

1987 ◽  
Vol 33 (115) ◽  
pp. 315-318 ◽  
Author(s):  
Stefan Hastenrath
Keyword(s):  
Vertical Flow ◽  
Glacier Surface ◽  
Ice Flow ◽  
Ice Surface ◽  
Mass Redistribution ◽  
Observation Program ◽  
Glacier Ice ◽  
Long Term Observation

AbstractThe second 4 year phase of a long-term observation program on Lewis Glacier, Mount Kenya, was completed in March 1986. As for the 1978–82 interval, net-balance results at a stake network and repeated mapping of the ice-surface topography allowed assessment of the mass economy by both “glaciological” and “geodetic” methods.The general findings from the 1978–82 observations are confirmed: the vertical flow component is directed downward in the upper glacier, and upward in the lower glacier; surface lowering and negative net balance increase down-glacier; ice flow mitigates surface lowering by the negative net balance in the lower glacier, but enhances it in the upper glacier. However, the major difference between the 1982–86 and 1978–82 periods is the progressive slow-down of ice flow. This entails a reduction of mass redistribution, in consequence of which the surface lowering becomes increasingly dependent on thein-situnet balance. It is expected that this circumstance will simplify any inference on future glacier behavior.

scholarly journals 3-D surface properties of glacier penitentes over an ablation season, measured using a Microsoft Xbox Kinect

2016 ◽  
Vol 10 (5) ◽  
pp. 1897-1913 ◽  
Author(s):  
Lindsey I. Nicholson ◽  
Michał Pętlicki ◽  
Ben Partan ◽  
Shelley MacDonell
Keyword(s):  
Wind Direction ◽  
Laser Scanning ◽  
Morphological Changes ◽  
Roughness Element ◽  
Three Dimensional ◽  
Small Scale ◽  
Glacier Surface ◽  
Transverse Profile ◽  
Glacier Ice ◽  
Xbox Kinect

Abstract. In this study, the first small-scale digital surface models (DSMs) of natural penitentes on a glacier surface were produced using a Microsoft Xbox Kinect sensor on Tapado Glacier, Chile (30°08′ S, 69°55′ W). The surfaces produced by the complete processing chain were within the error of standard terrestrial laser scanning techniques, but insufficient overlap between scanned sections that were mosaicked to cover the sampled areas can result in three-dimensional (3-D) positional errors of up to 0.3 m. Between November 2013 and January 2014 penitentes become fewer, wider and deeper, and the distribution of surface slope angles becomes more skewed to steep faces. Although these morphological changes cannot be captured by manual point measurements, mean surface lowering of the scanned areas was comparable to that derived from manual measurements of penitente surface height at a minimum density of 5 m−1 over a 5 m transverse profile. Roughness was computed on the 3-D surfaces by applying two previously published geometrical formulae: one for a 3-D surface and one for single profiles sampled from the surface. Morphometric analysis shows that skimming flow is persistent over penitentes, providing conditions conducive for the development of a distinct microclimate within the penitente troughs. For each method a range of ways of defining the representative roughness element height was used, and the calculations were done both with and without application of a zero displacement height offset to account for the likelihood of skimming air flow over the closely spaced penitentes. The computed roughness values are on the order of 0.01–0.10 m during the early part of the ablation season, increasing to 0.10–0.50 m after the end of December, in line with the roughest values previously published for glacier ice. Both the 3-D surface and profile methods of computing roughness are strongly dependent on wind direction. However, the two methods contradict each other in that the maximum roughness computed for the 3-D surface coincides with airflow across the penitente lineation, while maximum roughness computed for sampled profiles coincides with airflow along the penitente lineation. These findings highlight the importance of determining directional roughness and wind direction for strongly aligned surface features and also suggest more work is required to determine appropriate geometrical roughness formulae for linearized features.

scholarly journals Radar-detected englacial stratigraphy in the Pensacola Mountains, Antarctica: implications for recent changes in ice flow and accumulation

2013 ◽  
Vol 54 (63) ◽  
pp. 91-100 ◽  
Author(s):  
Seth Campbell ◽  
Greg Balco ◽  
Claire Todd ◽  
Howard Conway ◽  
Kathleen Huybers ◽  
...  
Keyword(s):  
Mass Balance ◽  
Surface Elevation ◽  
Ice Flow ◽  
Ice Surface ◽  
Valley Glacier ◽  
Glacier Ice ◽  
Elevation Changes ◽  
Ice Sheet Dynamics ◽  
Surface Ice ◽  
Ground Penetrating

AbstractWe used measurements of radar-detected stratigraphy, surface ice-flow velocities and accumulation rates to investigate relationships between local valley-glacier and regional ice-sheet dynamics in and around the Schmidt Hills, Pensacola Mountains, Antarctica. Ground-penetrating radar profiles were collected perpendicular to the long axis of the Schmidt Hills and the margin of Foundation Ice Stream (FIS). Within the valley confines, the glacier consists of blue ice, and profiles show internal stratigraphy dipping steeply toward the nunataks and truncated at the present-day ablation surface. Below the valley confines, the blue ice is overlain by firn. Data show that upward-progressing overlap of actively accumulating firn onto valley-glacier ice is slightly less than ice flow out of the valleys over the past ∼1200 years. The apparent slightly negative mass balance (-0.25 cm a-1) suggests that ice-margin elevations in the Schmidt Hills may have lowered over this time period, even without a change in the surface elevation of FIS. Results suggest that (1) mass-balance gradients between local valley glaciers and regional ice sheets should be considered when using local information to estimate regional ice surface elevation changes; and (2) interpretation of shallow ice structures imaged with radar can provide information about local ice elevation changes and stability.

scholarly journals INVESTIGATION OF MOUNTAIN GLACIER STORAGE AND ITS CHANGES DURING 2000–2016 IN THE WESTERN TIBETAN PLATEAU USING COMBINED GROUND AND SATELLITE OBSERVATIONS

2019 ◽  
Vol XLII-2/W13 ◽  
pp. 1817-1823
Author(s):  
Y. Zhang ◽  
X. Zou ◽  
H. Gao
Keyword(s):  
Thickness Distribution ◽  
Water Volume ◽  
Ice Thickness ◽  
Volume Distribution ◽  
Elevation Change ◽  
Glacier Surface ◽  
Mountain Glacier ◽  
Discharge Data ◽  
Change Rate ◽  
Glacier Ice

<p><strong>Abstract.</strong> The Upper Indus River Basin (UIB) has developed the largest midlatitude mountain glaciers worldwide. Ice thickness and volume distribution are important prerequisites for glaciological and hydrological investigations. In this paper, we presented detailed estimates of ice thickness in UIB region. Using ground penetrating radar, we measured glacier ice thickness on six typical glaciers; we obtained the parameters of the GlabTOP2 from these measurements and analyzed its uncertainty. Using the verified GlabTOP2 model, we simulated glacier ice thickness and volume in UIB subcatchments. The simulated results indicated that the UIB glacier thickness distribution was not uniform, ranging from 0 to 488&amp;thinsp;m, with an average thickness of 78&amp;thinsp;m. Total volume was defined as 1269.70&amp;thinsp;km<sup>3</sup> in 2000, which corresponded to 1142.73&amp;thinsp;km<sup>3</sup> water volume. According to the calculated discharge data from the Besham hydrological station, the total glacier volume of UIB generally can supply water resources for the downstream area for at least 15 years. And the glacier surface elevations generally decreased from 2000 to 2016 in UIB subbasins, although there was significant spatial heterogeneity in the seven subcatchments. The annual glacier surface elevation change rate of the Hindu Kush area was the smallest, followed by that of the Karakoram. The greatest glacier elevation change rate was observed in the Western Himalaya, indicating rapid glacial melting.</p>

scholarly journals On the Relation of Net Balance, Ice Flow, and Surface Lowering of Lewis Glacier, Mount Kenya, East Africa, 1982–86

1987 ◽  
Vol 33 (115) ◽  
pp. 315-318 ◽  
Author(s):  
Stefan Hastenrath
Keyword(s):  
Vertical Flow ◽  
Glacier Surface ◽  
Ice Flow ◽  
Ice Surface ◽  
Mass Redistribution ◽  
Observation Program ◽  
Glacier Ice ◽  
Long Term Observation

AbstractThe second 4 year phase of a long-term observation program on Lewis Glacier, Mount Kenya, was completed in March 1986. As for the 1978–82 interval, net-balance results at a stake network and repeated mapping of the ice-surface topography allowed assessment of the mass economy by both “glaciological” and “geodetic” methods.The general findings from the 1978–82 observations are confirmed: the vertical flow component is directed downward in the upper glacier, and upward in the lower glacier; surface lowering and negative net balance increase down-glacier; ice flow mitigates surface lowering by the negative net balance in the lower glacier, but enhances it in the upper glacier. However, the major difference between the 1982–86 and 1978–82 periods is the progressive slow-down of ice flow. This entails a reduction of mass redistribution, in consequence of which the surface lowering becomes increasingly dependent on the in-situ net balance. It is expected that this circumstance will simplify any inference on future glacier behavior.

In-situ automatic observations of ice thickness of seas

2012 ◽  
Vol 19 (3) ◽  
pp. 583-592 ◽  
Author(s):  
Yinke Dou ◽  
Xiaomin Chang
Keyword(s):  
Sea Ice ◽  
New Technologies ◽  
Capacitive Sensor ◽  
Automatic Monitoring ◽  
Ice Thickness ◽  
In Situ Observation ◽  
Glacier Surface ◽  
Sea Ice Thickness ◽  
Surface Ice

Abstract Ice thickness is one of the most critical physical indicators in the ice science and engineering. It is therefore very necessary to develop in-situ automatic observation technologies of ice thickness. This paper proposes the principle of three new technologies of in-situ automatic observations of sea ice thickness and provides the findings of laboratory applications. The results show that the in-situ observation accuracy of the monitor apparatus based on the Magnetostrictive Delay Line (MDL) principle can reach ±2 mm, which has solved the “bottleneck” problem of restricting the fine development of a sea ice thermodynamic model, and the resistance accuracy of monitor apparatus with temperature gradient can reach the centimeter level and research the ice and snow substance balance by automatically measuring the glacier surface ice and snow change. The measurement accuracy of the capacitive sensor for ice thickness can also reach ±4 mm and the capacitive sensor is of the potential for automatic monitoring the water level under the ice and the ice formation and development process in water. Such three new technologies can meet different needs of fixed-point ice thickness observation and realize the simultaneous measurement in order to accurately judge the ice thickness.

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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