scholarly journals A 1 year record of global radiation and albedo in the ablation zone of Morteratschgletscher, Switzerland

1998 ◽  
Vol 44 (147) ◽  
pp. 231-238 ◽  
Author(s):  
J. Oerlemans ◽  
W. H. Knap
Keyword(s):  
Snow Depth ◽  
Global Radiation ◽  
Glacier Mass Balance ◽  
Control Parameters ◽  
Ablation Zone ◽  
Atmospheric Attenuation ◽  
Glacier Surface ◽  
Mass Balance Models ◽  
Optimal Values ◽  
Analyse Data

AbstractWe analyse data on solar radiation measured with an automatic weather station on Morteratschgletscher, Switzerland, for the period 1 October 1995–30 September 1996. The station is in the lower ablation zone. Due to shading by surrounding mountains and atmospheric attenuation, only 49% of the annual extraterrestrial irradiance (mean: 292 W m−2) reaches the glacier surface. About 48% of this is absorbed at the surface (mean: 79 W m−2; annual albedo of 0.53).We present a simple albedo scheme for use in glacier mass-balance models. We fit the model to the 1 year dataset by optimizing five control parameters (optimal values in brackets): albedo of snow (0.75), albedo of firn (0.53), albedo of ice (0.34),e-folding constant for effect of ageing on snow albedo (21.9 days) ande-folding constant for effect of snow depth on albedo (3.2 cm). The input consists of daily albedo, snow depth and dates of snowfall events. The correlation coefficient between observed and simulated albedo is 0.931, the corresponding rms difference being 0.067.

scholarly journals A 1 year record of global radiation and albedo in the ablation zone of Morteratschgletscher, Switzerland

1998 ◽  
Vol 44 (147) ◽  
pp. 231-238 ◽  
Author(s):  
J. Oerlemans ◽  
W. H. Knap
Keyword(s):  
Snow Depth ◽  
Global Radiation ◽  
Glacier Mass Balance ◽  
Control Parameters ◽  
Ablation Zone ◽  
Atmospheric Attenuation ◽  
Glacier Surface ◽  
Mass Balance Models ◽  
Optimal Values ◽  
Analyse Data

AbstractWe analyse data on solar radiation measured with an automatic weather station on Morteratschgletscher, Switzerland, for the period 1 October 1995–30 September 1996. The station is in the lower ablation zone. Due to shading by surrounding mountains and atmospheric attenuation, only 49% of the annual extraterrestrial irradiance (mean: 292 W m−2) reaches the glacier surface. About 48% of this is absorbed at the surface (mean: 79 W m−2; annual albedo of 0.53).We present a simple albedo scheme for use in glacier mass-balance models. We fit the model to the 1 year dataset by optimizing five control parameters (optimal values in brackets): albedo of snow (0.75), albedo of firn (0.53), albedo of ice (0.34), e-folding constant for effect of ageing on snow albedo (21.9 days) and e-folding constant for effect of snow depth on albedo (3.2 cm). The input consists of daily albedo, snow depth and dates of snowfall events. The correlation coefficient between observed and simulated albedo is 0.931, the corresponding rms difference being 0.067.

scholarly journals Glacier Mass Balance in the Nyainqentanglha Mountains between 2000 and 2017 Retrieved from ZiYuan-3 Stereo Images and the SRTM DEM

2020 ◽  
Vol 12 (5) ◽  
pp. 864 ◽  
Author(s):  
Shaoting Ren ◽  
Massimo Menenti ◽  
Li Jia ◽  
Jing Zhang ◽  
Jingxiao Zhang ◽  
...  
Keyword(s):  
Mass Loss ◽  
Mass Balance ◽  
Glacier Mass Balance ◽  
The Tibetan Plateau ◽  
Ablation Zone ◽  
Mass Balances ◽  
Srtm Dem ◽  
Stereo Images ◽  
Glacier Surface ◽  
Accumulation Zone

Mountain glaciers are excellent indicators of climate change and have an important role in the terrestrial water cycle and food security in many parts of the world. Glaciers are the major water source of rivers and lakes in the Nyainqentanglha Mountains (NM) region, where the glacier area has the second largest extent on the Tibetan Plateau. The potential of the high spatial resolution ZiYuan-3 (ZY-3) Three-Line-Array (TLA) stereo images to retrieve glacier mass balance has not been sufficiently explored. In this study, we optimized the procedure to extract a Digital Elevation Model (DEM) from ZY-3 TLA stereo images and estimated the geodetic mass balance of representative glaciers in the two typical areas of the NM using ZY-3 DEMs and the C-band Shuttle Radar Topography Mission (SRTM) DEM in three periods, i.e., 2000–2013, 2013–2017 and 2000–2017. The results provide detailed information towards better understanding of glacier change and specifically show that: (1) with our new stereo procedure, ZY-3 TLA data can significantly increase point cloud density and decrease invalid data on the glacier surface map to generate a high resolution (5 m) glacier mass balance map; (2) the glacier mass balance in both the Western Nyainqentanglha Mountains (WNM) and Eastern Nyainqentanglha Mountains (ENM) was negative in 2000–2017, and experienced faster mass loss in recent years (2013–2017) in the WNM. Overall, the glaciers in the western and eastern NM show different change patterns since they are influenced by different climate regimes; the glacier mass balances in WNM was –0.22 ± 0.23 m w.e. a−1 and –0.43 ± 0.06 m w.e. a−1 in 2000–2013 and 2013–2017, respectively, while in 2000–2017, it was –0.30 ± 0.19 m w.e. a−1 in the WNM and –0.56 ± 0.20 m w.e. a−1 in the ENM; (3) in the WNM, the glaciers experienced mass loss in 2000–2013 and 2013–2017 in the ablation zone, while in the accumulation zone mass increased in 2000–2013 and a large mass loss occurred in 2013–2017; as regards the ENM, the glacier mass balance was negative in 2000–2017 in both zones; (4) glacier mass balance can be affected by the fractional abundance of debris and glacier slope; (5) the glacier mass balances retrieved by ZY-3 and TanDEM-X data agreed well in the ablation zone, while a large difference occurred in the accumulation zone because of the snow/firn penetration of the X-band SAR signal.

Debris-induced stagnation and ensuing morphological evolution of a central Himalayan glacier

2021 ◽  
Author(s):  
Purushottam Kumar Garg ◽  
Aparna Shukla ◽  
Santosh Kumar Rai ◽  
Jairam Singh Yadav
Keyword(s):  
Remote Sensing ◽  
Morphological Evolution ◽  
Remote Sensing Data ◽  
Google Earth ◽  
Lateral Moraine ◽  
Central Himalaya ◽  
Ablation Zone ◽  
Glacier Surface ◽  
Glacier System ◽  
Debris Cover

<p>This study presents field evidences (October 2018) and remote sensing measurements (2000-2020) to show stagnant conditions of lower ablation zone (LAZ) of the ‘companion glacier’, central Himalaya, India and its implication on the morphological evolution. The Companion glacier is named so as it accompanied the Chorabari glacier (widely studied benchmark glacier in the central Himalaya) in the distant past. Supraglacial debris thickness, supraglacial ponds anf other morphological features (e.g. lateral moraine height, supraglacial mounds) were measured/observed in the field. Glacier area, length, debris extent, surface elevation change and surface ice velocity were estimated using satellite remote sensing data from Landsat-TM/ETM+/OLI, Sentinel-MSI, Terra-ASTER and SRTM, Cartosat-1 and Google Earth images. Results show that the glacier has very small accumulation area and it is mainly fed by avalanches. The headwall of glacier is very steep which causes frequent avalanches leading to voluminous debris addition to the glacier system. Consequently, about 80% area of the glacier is debris-covered. The debris is very thick in the LAZ exceeding several meters in the LAZ and comprised of big boulders making debris thickness measurements practically impossible particularly in the snout region. However, debris thickness decreases with increasing distance from the snout and is in the order of 20-40 cm at about 2.5 km upglacier. The huge debris cover has protected the glacier ice from rapid melting. That’s why surface lowering of the glacier is less as compared to nearby Chorabari glacier. Moreover, due to (a) less mass supply from upper reaches and (b) huge debris cover, the glacier movement is very slow. The movement is too low that is allowed vegetation (some big grasses with wooded stems) to grow and survive on the glacier surface. The slow moving LAZ also causing bulging on the upper ablation zone (UAZ). Consequently, several mounds have developed on the UAZ. Thin debris slides down from mounds exposing the ice underneath for melting. Owing to these processes, spot melting is now a dominant mechanism of glacier wastage in the companion glacier. Thus, it can be summarized that careful field observations along with remote sensing estimates can be very important for understanding the glacier evolution.</p>

scholarly journals Geodetic Mass Balance of Haxilegen Glacier No. 51, Eastern Tien Shan, from 1964 to 2018

2022 ◽  
Vol 14 (2) ◽  
pp. 272
Author(s):  
Chunhai Xu ◽  
Zhongqin Li ◽  
Feiteng Wang ◽  
Jianxin Mu ◽  
Xin Zhang
Keyword(s):  
Mass Loss ◽  
Mass Balance ◽  
Laser Scanning ◽  
Mean Value ◽  
Tien Shan ◽  
Glacier Mass Balance ◽  
Topographic Map ◽  
Glacier Surface ◽  
Elevation Changes ◽  
Geodetic Mass Balance

The eastern Tien Shan hosts substantial mid-latitude glaciers, but in situ glacier mass balance records are extremely sparse. Haxilegen Glacier No. 51 (eastern Tien Shan, China) is one of the very few well-measured glaciers, and comprehensive glaciological measurements were implemented from 1999 to 2011 and re-established in 2017. Mass balance of Haxilegen Glacier No. 51 (1999–2015) has recently been reported, but the mass balance record has not extended to the period before 1999. Here, we used a 1:50,000-scale topographic map and long-range terrestrial laser scanning (TLS) data to calculate the area, volume, and mass changes for Haxilegen Glacier No. 51 from 1964 to 2018. Haxilegen Glacier No. 51 lost 0.34 km2 (at a rate of 0.006 km2 a−1 or 0.42% a−1) of its area during the period 1964–2018. The glacier experienced clearly negative surface elevation changes and geodetic mass balance. Thinning occurred almost across the entire glacier surface, with a mean value of −0.43 ± 0.12 m a−1. The calculated average geodetic mass balance was −0.36 ± 0.12 m w.e. a−1. Without considering the error bounds of mass balance estimates, glacier mass loss over the past 50 years was in line with the observed and modeled mass balance (−0.37 ± 0.22 m w.e. a−1) that was published for short time intervals since 1999 but was slightly less negative than glacier mass loss in the entire eastern Tien Shan. Our results indicate that Riegl VZ®-6000 TLS can be widely used for mass balance measurements of unmonitored individual glaciers.

Temperate Alpine glacier surface dynamics linked to collapsing subglacial conduits

2021 ◽  
Author(s):  
Pascal Egli ◽  
Stuart Lane ◽  
James Irving ◽  
Bruno Belotti
Keyword(s):  
Three Dimensional ◽  
Swiss Alps ◽  
Glacier Retreat ◽  
Collapse Mechanism ◽  
Glacier Mass Balance ◽  
Glacier Surface ◽  
Alpine Glacier ◽  
Surface Loss ◽  
Ice Surface ◽  
Surface Melt

<p>If tongues of temperate Alpine glaciers are subjected to high temperatures their topography may change rapidly due to the effects of differential melt related to aspect and debris cover. Independent of local surface melt, the position of subglacial conduits may have an important influence on ice creep and so on changes in topography at the ice surface. This reflects analyses that suggest that subglacial conduits at glacier margins may not be permanently pressurised; and that creep closure rates are insufficient to close subglacial conduits completely. Rapid climate warming may exacerbate this process, due both to surface-melt driven glacier thinning and over-enlargement of conduits due to high upstream melt rates. Over-enlarged conduits that are not permanently pressurised would lead to the development of structural weaknesses and eventual collapse of the ice surface into the conduits. We hypothesise that this collapse mechanism could represent an important and alternative driver of rapid glacier retreat.</p><p>In this paper we combine: (1) an extensive survey of glacier margin collapse in the Swiss Alps with (2) intensive monitoring of the dynamics of such collapse at the Otemma Glacier in the south-western Swiss Alps. Daily UAV surveys were undertaken at a high spatial resolution and with precise and accurate ground control. These datasets were used to generate surface change information using SfM-MVS photogrammetry. Surfaces of difference showed surface loss that could not be related to ablation alone. Combining them with three-dimensional ground-penetrating radar (GPR) surveys in the same zone showed that the surface loss was coincident spatially with the positions of sub-glacial conduits, for ice thicknesses between 20 m and 50 m. We show that this form of subglacial conduit collapse is also happening for several other glaciers in the Swiss Alps, and that this mechanism of snout collapse and glacier retreat has become more common than has hitherto been the case. It also leads to temporal patterns of glacier margin retreat that differ from those that might be expected due to glacier mass balance and ice mass flux effects alone.</p>

scholarly journals Surface melt and the importance of water flow – an analysis based on high-resolution unmanned aerial vehicle (UAV) data for an Arctic glacier

2020 ◽  
Vol 14 (2) ◽  
pp. 549-563 ◽  
Author(s):  
Eleanor A. Bash ◽  
Brian J. Moorman
Keyword(s):  
Water Flow ◽  
Model Performance ◽  
Model Error ◽  
Two Dimensions ◽  
Glacier Mass Balance ◽  
Glacier Surface ◽  
Technological Advances ◽  
Flow Features ◽  
Surface Melt ◽  
The Difference

Abstract. Models of glacier surface melt are commonly used in studies of glacier mass balance and runoff; however, with limited data available, most models are validated based on ablation stakes and data from automatic weather stations (AWSs). The technological advances of unmanned aerial vehicles (UAVs) and structure from motion (SfM) have made it possible to measure glacier surface melt in detail over larger portions of a glacier. In this study, we use melt measured using SfM processing of UAV imagery to assess the performance of an energy balance (EB) and enhanced temperature index (ETI) melt model in two dimensions. Imagery collected over a portion of the ablation zone of Fountain Glacier, Nunavut, on 21, 23, and 24 July 2016 was previously used to determine distributed surface melt. An AWS on the glacier provides some measured inputs for both models as well as an additional check on model performance. Modelled incoming solar radiation and albedo derived from UAV imagery are also used as inputs for both models, which were used to estimate melt from 21 to 24 July 2016. Both models estimate total melt at the AWS within 16 % of observations (4 % for ETI). Across the study area the median model error, calculated as the difference between modelled and measured melt (EB = −0.064 m, ETI = −0.050 m), is within the uncertainty of the measurements. The errors in both models were strongly correlated to the density of water flow features on the glacier surface. The relation between water flow and model error suggests that energy from surface water flow contributes significantly to surface melt on Fountain Glacier. Deep surface streams with highly asymmetrical banks are observed on Fountain Glacier, but the processes leading to their formation are missing in the model assessed here. The failure of the model to capture flow-induced melt would lead to significant underestimation of surface melt should the model be used to project future change.

scholarly journals Solar radiation, cloudiness and longwave radiation over low-latitude glaciers: implications for mass-balance modelling

2009 ◽  
Vol 55 (190) ◽  
pp. 292-302 ◽  
Author(s):  
Thomas Mölg ◽  
Nicolas J. Cullen ◽  
Georg Kaser
Keyword(s):  
Mass Balance ◽  
Global Radiation ◽  
Longwave Radiation ◽  
Balance Model ◽  
Glacier Mass Balance ◽  
Peruvian Andes ◽  
Tropical Glaciers ◽  
Clear Sky ◽  
Physically Based ◽  
Radiation Parameterizations

AbstractBroadband radiation schemes (parameterizations) are commonly used tools in glacier mass-balance modelling, but their performance at high altitude in the tropics has not been evaluated in detail. Here we take advantage of a high-quality 2 year record of global radiation (G ) and incoming longwave radiation (L ↓) measured on Kersten Glacier, Kilimanjaro, East Africa, at 5873 m a.s.l., to optimize parameterizations of G and L ↓. We show that the two radiation terms can be related by an effective cloud-cover fraction neff , so G or L ↓ can be modelled based on neff derived from measured L ↓ or G, respectively. At neff = 1, G is reduced to 35% of clear-sky G, and L ↓ increases by 45–65% (depending on altitude) relative to clear-sky L ↓. Validation for a 1 year dataset of G and L ↓ obtained at 4850 m on Glaciar Artesonraju, Peruvian Andes, yields a satisfactory performance of the radiation scheme. Whether this performance is acceptable for mass-balance studies of tropical glaciers is explored by applying the data from Glaciar Artesonraju to a physically based mass-balance model, which requires, among others, G and L ↓ as forcing variables. Uncertainties in modelled mass balance introduced by the radiation parameterizations do not exceed those that can be caused by errors in the radiation measurements. Hence, this paper provides a tool for inclusion in spatially distributed mass-balance modelling of tropical glaciers and/or extension of radiation data when only G or L ↓ is measured.

scholarly journals Characteristics of the lower ablation zone of the West Greenland ice sheet for energy-balance modelling

1996 ◽  
Vol 23 ◽  
pp. 160-166 ◽  
Author(s):  
Michiel van den Broeke
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Global Radiation ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Longwave Radiation ◽  
Turbulent Fluxes ◽  
Ablation Zone ◽  
The West ◽  
West Greenland

In this paper, we present the summer-time energy balance for a site in the lower ablation zone of the West Greenland ice sheet. The summer climate of this part of Greenland is sunny and dry. The energy that is available for melting (on average 174 W m−2or 4.5 cm w.e.d−1) is mainly provided by net global radiation two-thirds and sensible-heat flux (one-third). The contribution of the sub-surface heat flux, the latent-heat flux and the net longwave radiation to the energy balance are small. We tested some parameterizations to calculate energy-balance components that are currently used in general circulation models, energy-balance models and mesoscale meteorological models. For the area and time period under consideration, parameterizations that use screen-level temperature for the calculation of incoming longwave radiation systematically underestimate this quantity by 10 W m−2owing to the proximity of the melting-ice surface that restricts temperature increase of the lowest air layers. The incoming global radiation was predicted correctly. Simple explicit schemes that calculate the stability corrections for turbulent fluxes as a function of the bulk Richardson number tend to underestimate the turbulent fluxes by 15 W m−2. The aerodynamic roughness lengthz0derived from wind-speed profiles appears to be erroneously small, leading to underestimation of the fluxes by 30 W m−2. Probably, the wind profile is distorted by the rough terrain. An estimate ofz0biased on microtopographical survey yielded a more realistic result. Because all errors work in the same direction, the use of some of the parameterizations can cause serious underestimation of the melting energy.

scholarly journals Radiation measurement at Lewis Glacier, Mount Kenya, Kenya

1980 ◽  
Vol 25 (93) ◽  
pp. 439-444 ◽  
Author(s):  
Stefan Hastenrath ◽  
J. K. Patnaik
Keyword(s):  
Global Radiation ◽  
Short Wave ◽  
Steep Slope ◽  
Horizontal Component ◽  
Wave Radiation ◽  
Short Wave Radiation ◽  
Glacier Surface ◽  
Rock Face ◽  
Long Wave ◽  
Long Wave Radiation

AbstractShort- and long-wave radiation on variously oriented vertical surfaces, direct solar radiation, global radiation, and long–wave radiation on a horizontal surface were measured on Lewis Glacier, Mount Kenya, at 4800 m. For the orientation of vertical surfaces, the following azimuths were selected: 45°, facing the steep slope of the upper glacier; 135°, facing a rock ridge and some glacier surface in the foreground; 225°, facing down–glacier towards the Teleki valley with open sky occupying much of the view; and 315°, directed towards the steep south-east face of the Nelion peak.The horizontal components of diffuse short-wave radiation reach a magnitude comparable to those of direct radiation. As a result of contrastingly different albedos of natural surfaces, the horizontal component of diffuse short–wave radiation is particularly large from the direction of the upper glacier, with values around 330–500 W m−2, and smallest from the direction of the rock face of Nelion peak, where values are around 150–330 W m−2. Long–wave radiation seems enhanced from the direction of the Nelion face, and reduced from the azimuth of the upper glacier, thus apparently reflecting differences in emissivity and temperature.

scholarly journals Ice Loss in the Ablation Area of a Himalayan Glacier; Studies on Miar Glacier, Karakoram Mountains, Pakistan

1989 ◽  
Vol 13 ◽  
pp. 289-293 ◽  
Author(s):  
G.J. Young ◽  
J.P. Schmok
Keyword(s):  
Stream Flow ◽  
Equilibrium Line ◽  
Glacier Mass Balance ◽  
Indus River ◽  
Glacier Surface ◽  
Transverse Profile ◽  
Karakoram Mountains ◽  
Sampling Problems ◽  
Independent Assessment ◽  
Made In

One of the main aims of the Snow and Ice Hydrology Project, a joint Canada-Pakistan endeavour, is to estimate ice loss in the ablation areas of glaciers in order to predict with greater confidence stream flow in the headwaters of the Indus River. To this end, Miar Glacier, located in the central Karakoram Range, north of Gilgit, was intensively studied during the summers of 1986 and 1987. Measurements of glacier mass balance by the monitoring of accumulation and ablation at stake locations is very difficult in the Himalyan environment. It is usually almost impossible to reach elevations above the equilibrium line without major effort, and always very difficult once there to make meaningful measurements; the ablation areas are often heavily crevassed and/or debris-covered, and this poses difficult sampling problems. The method used in this study was to monitor annual surface movement on a cross-profile as near as possible to the equilibrium line. The measurements, obtained in conjunction with depth soundings made on the same profile, allow the annual ice flux through the cross-profile to be calculated. If an approximately steady-state glacier is assumed, it would be expected that this flux would be roughly equivalent to the rate of ice loss below the profile. The movements of wooden stakes drilled into the glacier were monitored throughout each of the summers and, since two of the stakes survived the intervening winter, this allowed calculation of annual movement. Distances between the crests of ogives were also surveyed, providing an independent assessment of glacier movement. Depth measurements by radio-echo sounder were successfully made in the summer of 1987, showing maximum ice depths of 550 m. The annual ice flux through the transverse profile was estimated as 5.67 × 107 m3, which corresponds to a mean annual ice loss from the glacier surface below the profile of 8.10 m of ice.

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