scholarly journals Modeling Supraglacial Ponding and Drainage Dynamics: Responses to Glacier Surface Topography and Debris Flux Conditions

2021 ◽  
Author(s):  
Da Huo ◽  
Michael P. Bishop
Keyword(s):  
Surface Topography ◽  
Radiative Forcing ◽  
Field Measurements ◽  
Climate Forcing ◽  
Ablation Zone ◽  
Glacier Surface ◽  
Surface Gradient ◽  
Glacier Changes ◽  
Debris Transport ◽  
Topographic Depressions

Abstract. Supraglacial ponds play a significant role in the mass loss of many debris-covered glaciers in the Himalaya. Glacier surface topography and debris flux conditions are thought to govern supraglacial ponding and drainage. Existing studies, however, have not adequately investigated the relationships and feedbacks between meltwater production, debris transport, topographic evolution and ponding, because field measurements are limited in time and space, and most existing models either neglect these processes or use oversimplified assumptions. Such limitations restrict our understanding of supraglacial hydrology and introduce uncertainties in our assessments of glacier sensitivity to climate forcing. This study develops a more comprehensive numerical model to provide insights into the couplings between topographically-controlled surface ablation, meltwater drainage, ponding, and gravitational debris transport under radiative forcing. We investigate supraglacial ponding and drainage dynamics in response to different topographic and debris flux conditions through numerical simulations based on Baltoro Glacier in the Karakoram and several hypothetical scenarios. Results suggest that: 1) Supraglacial ponds make a significant contribution to the total ice loss (more than 20 %) in the lower-mid ablation zone over one ablation season, which elevates the glacier's nonlinear response to radiative forcing. 2) Gravitational debris transport has a non-negligible control on the growth rate of supraglacial ponds by governing debris thickness and ablation rates on the ice-cliffs around ponds. 3) Glacier surface gradient and local topographic depressions control pond formation by affecting supraglacial water storage and drainage. Our simulations provide a possible explanation to the abundance of ponds in the mid ablation zone where slope is gentle and more local depressions are present. These findings may contribute to more accurate predictions of future glacier changes in response to climate change.

scholarly journals Amazonian BC Contribution to the Vallunaraju Glacier Surface Melt

2020 ◽  
Author(s):  
Wilmer Sánchez ◽  
Carl Schmitt ◽  
Alexzander Santiago ◽  
Gerles Medina
Keyword(s):  
Black Carbon ◽  
Forest Fires ◽  
Radiative Forcing ◽  
Dry Season ◽  
Decision Makers ◽  
Ablation Zone ◽  
Wet Season ◽  
Glacier Surface ◽  
Glacial Retreat

The role of Black Carbon (BC) as a contributor to glacial retreat is of particular interest to the scientific community and decision makers, due to its impact on snow albedo and glacier melt. In this study, a thermal-optical instrument (LAHM) was used to measure effective Black Carbon (eBC) in a series of surface snow samples collected from the Vallunaraju glacier, Cordillera Blanca, between April 2019 and May 2020. The time series obtained indicates a marked seasonal variability of eBC with maximum concentrations during the dry season and dramatic decrease during the wet season. The concentrations detected ranged between a minimum of 3.73 ng/g and 4.23 ng/g during the wet season and a maximum of 214.13 ng/g and 181.60 ng/g during the dry season, in the accumulation and ablation zone. Using SNICAR model, the reduction of albedo was estimated at 6.36% and 6.60% during the dry season and 0.68% and 0.95% during the wet season, which represents an average radiative forcing of 4.52 ± 1.84 W/m2 and 4.69 ± 1.59 W/m2 in the accumulation zone, and 0.49 ± 0.27 W/m2 and 0.68 ± 0.43 W/m2 in the ablation zone. The melting of snow due to the eBC translates into 80.18 ± 37.30 kg/m2 and 83.16 ± 32.75 kg/m2 during the dry season, and 7.91 ± 4.29 kg/m2 and 10.85 ± 6.62 kg/m2 during the wet season, in the accumulation and ablation zones, respectively. Finally, the HYSPLIT trajectory assessment shows that aerosols predominate in the Amazon rainforest, especially when forest fires are most abundant according to VIIRS images.

scholarly journals Estimation of Downwelling Surface Longwave Radiation under Heavy Dust Aerosol Sky

2016 ◽  
Author(s):  
Chunlei Wang ◽  
Bo-Hui Tang ◽  
Hua Wu ◽  
Ronglin Tang ◽  
Zhao-Liang Li
Keyword(s):  
Satellite Data ◽  
Land Surface ◽  
Radiative Forcing ◽  
Longwave Radiation ◽  
Field Measurements ◽  
Dust Aerosol ◽  
Climate Forcing ◽  
Proposed Model ◽  
Atmospheric Profile ◽  
Mean Square Errors

The variation of aerosols, especially dust aerosol, in time and space plays an important role in climate forcing studies. Aerosols can effectively reduce land surface longwave emission and re-emit energy at a colder temperature, making estimation of downwelling surface longwave radiation (DSLR) with satellite data difficult. Using the latest atmospheric radiative transfer code (MODTRAN 5.0), we simulate the outgoing longwave radiation (OLR) and DSLR under different land surface and atmospheric profile conditions. The results show that dust aerosol has an obvious “warming” effect to longwave radiation compared with other aerosols, that aerosol longwave radiative forcing (ALRF) increased with increasing aerosol optical depth (AOD), and that the atmospheric water vapor content (WVC) is critical to the understanding of ALRF. A method is proposed to improve the accuracy of DSLR estimation from satellite data for the skies under heavy dust aerosols. The AOD and atmospheric WVC under cloud-free conditions with a relatively simple satellite-based radiation model that yields the high accurate DSLR under heavy dust aerosol are used explicitly as model input to reduce the effects of dust aerosol on the estimation of DSLR. Validations of the proposed model with satellites data and field measurements show that it estimates the DSLR accurately under heavy dust aerosol skies. The root mean square errors (RMSEs) are 20.4 W/M2 and 24.2 W/M2 for Terra and Aqua satellites, respectively, at the Yingke site, and the biases are 2.7 W/M2 and 9.6 W/M2, respectively. For the Arvaikheer site, the RMSEs are 23.2 W/M2 and 19.8 W/M2 for Terra and Aqua, respectively, and the biases are 7.8 W/M2 and 10.5 W/M2, respectively. The proposed method is especially applicable to acquire relatively high accurate DSLR under heavy dust aerosol using MODIS data with available WVC and AOD data.

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 Combined impacts of current and future dust deposition and regional warming on Colorado River Basin snow dynamics and hydrology

2013 ◽  
Vol 17 (11) ◽  
pp. 4401-4413 ◽  
Author(s):  
J. S. Deems ◽  
T. H. Painter ◽  
J. J. Barsugli ◽  
J. Belnap ◽  
B. Udall
Keyword(s):  
River Basin ◽  
Radiative Forcing ◽  
Colorado River ◽  
Climate Forcing ◽  
Flow Volume ◽  
Prior Work ◽  
Climate Scenarios ◽  
Dust Deposition ◽  
Snow Albedo ◽  
Dust Loading

Abstract. The Colorado River provides water to 40 million people in seven western states and two countries and to 5.5 million irrigated acres. The river has long been overallocated. Climate models project runoff losses of 5–20% from the basin by mid-21st century due to human-induced climate change. Recent work has shown that decreased snow albedo from anthropogenic dust loading to the CO mountains shortens the duration of snow cover by several weeks relative to conditions prior to western expansion of the US in the mid-1800s, and advances peak runoff at Lees Ferry, Arizona, by an average of 3 weeks. Increases in evapotranspiration from earlier exposure of soils and germination of plants have been estimated to decrease annual runoff by more than 1.0 billion cubic meters, or ~5% of the annual average. This prior work was based on observed dust loadings during 2005–2008; however, 2009 and 2010 saw unprecedented levels of dust loading on snowpacks in the Upper Colorado River Basin (UCRB), being on the order of 5 times the 2005–2008 loading. Building on our prior work, we developed a new snow albedo decay parameterization based on observations in 2009/10 to mimic the radiative forcing of extreme dust deposition. We convolve low, moderate, and extreme dust/snow albedos with both historic climate forcing and two future climate scenarios via a delta method perturbation of historic records. Compared to moderate dust, extreme dust absorbs 2× to 4× the solar radiation, and shifts peak snowmelt an additional 3 weeks earlier to a total of 6 weeks earlier than pre-disturbance. The extreme dust scenario reduces annual flow volume an additional 1% (6% compared to pre-disturbance), a smaller difference than from low to moderate dust scenarios due to melt season shifting into a season of lower evaporative demand. The sensitivity of flow timing to dust radiative forcing of snow albedo is maintained under future climate scenarios, but the sensitivity of flow volume reductions decreases with increased climate forcing. These results have implications for water management and suggest that dust abatement efforts could be an important component of any climate adaptation strategies in the UCRB.

scholarly journals Impact of dust deposition on the albedo of Vatnajökull ice cap, Iceland

2017 ◽  
Vol 11 (2) ◽  
pp. 741-754 ◽  
Author(s):  
Monika Wittmann ◽  
Christine Dorothea Groot Zwaaftink ◽  
Louise Steffensen Schmidt ◽  
Sverrir Guðmundsson ◽  
Finnur Pálsson ◽  
...  
Keyword(s):  
Mass Balance ◽  
Radiative Forcing ◽  
Climate Model ◽  
Dispersion Model ◽  
Dust Deposition ◽  
Glacier Surface ◽  
Outlet Glacier ◽  
Ice Cap ◽  
Weather Stations ◽  
Dust Events

Abstract. Deposition of small amounts of airborne dust on glaciers causes positive radiative forcing and enhanced melting due to the reduction of surface albedo. To study the effects of dust deposition on the mass balance of Brúarjökull, an outlet glacier of the largest ice cap in Iceland, Vatnajökull, a study of dust deposition events in the year 2012 was carried out. The dust-mobilisation module FLEXDUST was used to calculate spatio-temporally resolved dust emissions from Iceland and the dispersion model FLEXPART was used to simulate atmospheric dust dispersion and deposition. We used albedo measurements at two automatic weather stations on Brúarjökull to evaluate the dust impacts. Both stations are situated in the accumulation area of the glacier, but the lower station is close to the equilibrium line. For this site ( ∼  1210 m a.s.l.), the dispersion model produced 10 major dust deposition events and a total annual deposition of 20.5 g m−2. At the station located higher on the glacier ( ∼  1525 m a.s.l.), the model produced nine dust events, with one single event causing  ∼  5 g m−2 of dust deposition and a total deposition of  ∼  10 g m−2 yr−1. The main dust source was found to be the Dyngjusandur floodplain north of Vatnajökull; northerly winds prevailed 80 % of the time at the lower station when dust events occurred. In all of the simulated dust events, a corresponding albedo drop was observed at the weather stations. The influence of the dust on the albedo was estimated using the regional climate model HIRHAM5 to simulate the albedo of a clean glacier surface without dust. By comparing the measured albedo to the modelled albedo, we determine the influence of dust events on the snow albedo and the surface energy balance. We estimate that the dust deposition caused an additional 1.1 m w.e. (water equivalent) of snowmelt (or 42 % of the 2.8 m w.e. total melt) compared to a hypothetical clean glacier surface at the lower station, and 0.6 m w.e. more melt (or 38 % of the 1.6 m w.e. melt in total) at the station located further upglacier. Our findings show that dust has a strong influence on the mass balance of glaciers in Iceland.

scholarly journals Assessment of co-benefits of black carbon emission reduction measures in Southeast Asia: Part 2 emission scenarios for 2030 and co-benefits on mitigation of air pollution and climate forcing

2017 ◽  
Author(s):  
Didin Agustian Permadi ◽  
Nguyen Thi Kim Oanh ◽  
Robert Vautard
Keyword(s):  
Southeast Asia ◽  
Black Carbon ◽  
Emission Reduction ◽  
Radiative Forcing ◽  
Crop Production ◽  
Cost Benefit Analysis ◽  
Climate Forcing ◽  
Agricultural Crop ◽  
Activity Data ◽  
Premature Deaths

Abstract. Following Part 1 (Permadi et al., 2017a) which focuses on the preparation of emission input data and evaluation of WRF/CHIMERE performance in 2007, this paper presents Part 2 of our research detailing the quantification of co-benefits resulted in the future (2030) from black carbon (BC) emission reduction measures for Southeast Asia (SEA) countries. The business as usual (BAU2030) projected emissions from the base year of 2007 (BY2007) assuming no intervention with the linear projection of the emissions based on the past decadal activity data (Indonesia and Thailand) and the sectoral GDP growth for other countries. The RED2030 featured measures to cut down emission in major four source sectors in Indonesia and Thailand (on-road transport, residential cooking, industry, and biomass open burning) while for other countries the representative concentration pathway 8.5 (RCP8.5) emissions were assumed. WRF/CHIMERE simulated levels of aerosol species under BAU2030 and RED2030 for the SEA domain using the base year meteorology and 2030 boundary conditions from LMDZ/INCA. The extended aerosol optical depth module (AODEM) calculated the total columnar AOD and BC AOD assuming the internal mixing state for the two future scenarios. Health benefits were analyzed in term of the avoided number of premature deaths associated with ambient PM2.5 reduction while the climate benefits were quantified using the reduction in the BC radiative forcing under RED2030. Under BAU2030, the average number of the premature deaths per 100,000 population in the domain would increase by 30 from BY2007 while under RED2030 the premature deaths would be cut-down (avoided) by 59 from the RED2030. In 2007, the maximum annual average BC radiative forcing in SEA countries was 0.98 W m−2 which would increase to 2.0 W m−2 under BAU2030 and 1.4 W m−2 under RED2030. Substantial co-benefits on human health and BC climate forcing reduction in SEA could be resulted from the emission measures incorporated in RED2030. Future works should consider other benefits such as for the agricultural crop production, and the cost benefit analysis of the measures implementation to provide relevant information for policy making.

scholarly journals Recent retreat of the Elbrus glacier system

2016 ◽  
Vol 62 (231) ◽  
pp. 94-102 ◽  
Author(s):  
IULIAN-HORIA HOLOBÂCĂ
Keyword(s):  
Summer Temperature ◽  
Glacier Area ◽  
Regression Analyses ◽  
Positive Relation ◽  
Glacier Surface ◽  
Glacier System ◽  
Digital Elevation ◽  
Glacier Changes ◽  
Global Land ◽  
Increasing Trend

The glacier system covering Europe's highest mountain, Elbrus, has exhibited an accelerated retreat since 1980. Some studies have related this retreat to a significant summer temperature increasing trend. Relief- and aspect-related parameters for the glacierized area have an important impact on glacier changes. In this paper, the changes in glacier area are identified, quantified and correlated with relief parameters for the period 1985–2007. Spatial analysis was performed using the GLAM-CD (Glacier Mapper – Change Detector) algorithm. The input data for this algorithm were Landsat 5 images, the Aster Global Digital Elevation and the glacier outlines from the GLIMS project (Global Land Ice Measurements from Space). Regression analyses between glacier area losses and relief-related parameters indicate a significant positive relation with the altitude and a significant negative relation with the glacier surface area. In this context, we used a correlated component regression to model these relations. The model explains >50% of the total variation.

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 new parameterization scheme of the real part of the ambient aerosols refractive index

2019 ◽  
Author(s):  
Gang Zhao ◽  
Tianyi Tan ◽  
Weilun Zhao ◽  
Song Guo ◽  
Ping Tian ◽  
...  
Keyword(s):  
Refractive Index ◽  
Radiative Forcing ◽  
Field Measurements ◽  
Effective Density ◽  
Parameterization Scheme ◽  
Chemical Components ◽  
Ambient Aerosols ◽  
Ambient Aerosol ◽  
The Real ◽  
Aerosol Radiative

Abstract. The refractive index of ambient aerosols, which directly determines the aerosol optical properties, is widely used in atmospheric models and remote sensing. Traditionally, the real part of the refractive index (RRI) is mainly parameterized by the measurement of ambient aerosol main inorganic components. In this paper, the characteristics of the ambient aerosol RRI are studied based on the field measurement in the East China. Results show that the ambient aerosol RRI varies significantly between 1.36 and 1.56. The direct aerosol radiative forcing is estimated to vary by 40 % corresponding to the variation of the measured aerosol RRI. We find that the ambient aerosol RRI is highly related with the aerosol effective density (ρeff) rather than the main chemical components. However, parameterization schemes of the ambient aerosol RRI by ρeff are not available due to the lack of corresponding simultaneous field measurements. For the first time, the size-resolved ambient aerosol RRI and ρeff are measured simultaneously by our designed measurement system. A new parameterization scheme of the ambient aerosols RRI using ρeff is proposed. The measured and parameterized RRI agree well with the correlation coefficient of 0.76. Knowledge of the ambient aerosol RRI would improve our understanding of the ambient aerosol radiative effects.

scholarly journals Impact of varying debris cover thickness on ablation: a case study for Koxkar Glacier in the Tien Shan

2014 ◽  
Vol 8 (2) ◽  
pp. 377-386 ◽  
Author(s):  
M. Juen ◽  
C. Mayer ◽  
A. Lambrecht ◽  
H. Han ◽  
S. Liu
Keyword(s):  
Remote Sensing ◽  
Field Measurements ◽  
Tien Shan ◽  
Shielding Effect ◽  
Glacier Surface ◽  
Glacier Terminus ◽  
Covered Area ◽  
Debris Cover ◽  
High Resolution Satellite Imagery ◽  
Cover Thickness

Abstract. To quantify the ablation processes on a debris covered glacier, a simple distributed ablation model has been developed and applied to a selected glacier. For this purpose, a set of field measurements was carried out to collect empirical data. A morphometric analysis of the glacier surface enables us to capture statistically the areal distribution of topographic features that influence debris thickness and consequently ablation. Remote-sensing techniques, using high-resolution satellite imagery, were used to extrapolate the in situ point measurements to the whole ablation area and to map and classify melt-relevant surface types. As a result, a practically applicable method is presented that allows the estimation of ablation on a debris covered glacier by combining field data and remote-sensing information. The sub-debris ice ablation accounts for about 24% of the entire ice ablation, while the percentage of the moraine covered area accounts for approximately 32% of the entire glacierized area. Although the ice cliffs occupy only 1.7% of the debris covered area, the melt amount accounts for approximately 12% of the total sub-debris ablation and 2.5% of the total ablation respectively. Our study highlights the influence of debris cover on the response of the glacier terminus in a particular climate setting. Due to the fact that melt rates beyond 0.1 m of moraine cover are highly restricted, the shielding effect of the debris cover dominates over the temperature and elevation dependence of the ablation in the bare ice case.

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