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Showing papers on "Accumulation zone published in 2019"


Journal ArticleDOI
TL;DR: This work studies in-situ meteorological drivers of glacial ablation at two sites in central Nepal, between 2013 and 2017, using data from six automatic weather stations (AWS).
Abstract: Temperature index (TI) models are convenient for modelling glacier ablation since they require only a few input variables and rely on simple empirical relations. The approach is generally assumed to be reliable at lower elevations (below 3500 m above sea level, a.s.l) where air temperature (Ta) relates well to the energy inputs driving melt. We question this approach in High Mountain Asia (HMA). We study in-situ meteorological drivers of glacial ablation at two sites in central Nepal, between 2013 and 2017, using data from six automatic weather stations (AWS). During the monsoon, surface melt dominates ablation processes at lower elevations (between 4950 and 5380 m a.s.l.). As net shortwave radiation (SWnet) is the main energy input at the glacier surface, albedo (α) and cloudiness play key roles while being highly variable in space and time. For these cases only, ablation can be calculated with a TI model, or with an Enhanced TI (ETI) model that includes a shortwave radiation (SW) scheme and site specific ablation factors. In the ablation zone during other seasons and during all seasons in the accumulation zone, sublimation and other wind-driven ablation processes also contribute to mass loss, and remain unresolved with TI or ETI methods.

60 citations


Journal ArticleDOI
TL;DR: Taking into account surface Stokes drift from a wave model reanalysis radically changes the fate of South Indian particles and changes the South Indian sensitive balance between Ekman convergence and turbulent diffusion processes.

37 citations


Journal ArticleDOI
TL;DR: Topsoil containing abundant BC was transported along the slope from the debris to the LG12 surface ice, and topsoil in this region could be lifted by strong mountain-valley winds and then deposited on snow/ice surfaces, which affected the LAP concentrations.

35 citations


Journal ArticleDOI
TL;DR: In this paper, the authors presented nine months of air temperature observations of the South Patagonia Icefield and showed that the ablation rates vary by up to 60% depending on the air temperature extrapolation method applied.
Abstract: The glaciers of Patagonia are the largest in South America and are shrinking rapidly, raising concerns about their contribution to sea‐level‐rise in the face of ongoing climatic change. However, modelling studies forecasting future glacier recession are limited by the scarcity of measured on‐glacier air temperatures, and thus tend to use spatially and temporally constant lapse rates. This study presents nine months of air‐temperature observations. The network consists of five automatic weather stations (AWS) and three on‐glacier air temperature sensors installed on the South Patagonia Icefield along a transect at 48° 45’ S. Observed lapse rates are, overall, steeper on the east (‐0.0072 °C m‐¹) compared to the west (‐0.0055 °C m‐¹) and vary between the lower section (tongue, ablation zone) and the upper section (plateau, accumulation zone) of the glaciers. Warmer off‐glacier temperatures are found in the east compared to the west for similar elevations. However, on‐glacier observations suggest that the glacier cooling effect is higher in the east compared to the west. Through application of distributed temperature‐index and point‐scale energy balance models we show that modelled ablation rates vary by up to 60%, depending on the air temperature extrapolation method applied, and that melt is overestimated and sublimation is underestimated if the glacier cooling effect is not included in the distributed air temperature data. These results can improve current and future modelling efforts of the energy and mass balance of the whole South Patagonia Icefield.

21 citations


Journal ArticleDOI
TL;DR: In this article, the Taylor Glacier (Antarctica) blue iceberg ice core was used to determine the ages of gas and air bubbles in the new ice cores by visually matching variations in gas and ice-phase tracers to preexisting ice core records.
Abstract: . New ice cores retrieved from the Taylor Glacier (Antarctica) blue ice area contain ice and air spanning the Marine Isotope Stage (MIS) 5–4 transition, a period of global cooling and ice sheet expansion. We determine chronologies for the ice and air bubbles in the new ice cores by visually matching variations in gas- and ice-phase tracers to preexisting ice core records. The chronologies reveal an ice age–gas age difference ( Δ age) approaching 10 ka during MIS 4, implying very low snow accumulation in the Taylor Glacier accumulation zone. A revised chronology for the analogous section of the Taylor Dome ice core (84 to 55 ka), located to the south of the Taylor Glacier accumulation zone, shows that Δ age did not exceed 3 ka. The difference in Δ age between the two records during MIS 4 is similar in magnitude but opposite in direction to what is observed at the Last Glacial Maximum. This relationship implies that a spatial gradient in snow accumulation existed across the Taylor Dome region during MIS 4 that was oriented in the opposite direction of the accumulation gradient during the Last Glacial Maximum.

19 citations


Journal ArticleDOI
TL;DR: In this paper, a correlation based Particle Image Velocimetry (PIV) technique has been used for the estimation of surface ice velocity of Chhota Shigri glacier using multiple window sizes in the same data-set.
Abstract: Information about the surface ice velocity is one of the important parameters for Mass balance and Glacier dynamics. This study estimates the surface ice velocity of Chhota Shigri glacier using Landsat (TM/ETM+) and ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) temporal data-sets from a period of 2009 to 2016 and 2006 to 2007, respectively. A correlation based Particle Image Velocimetry (PIV) technique has been used for the estimation of surface ice velocity. This technique uses multiple window sizes in the same data-set. Four window sizes (low, medium, high, very high) are used for each image pair. Estimated results have been compared with the published data. The outcomes attained from the medium window size closely matches with the published results. The estimated mean surface ice velocities of medium window size are 24 and 28.5 myr−1 for 2009/2010 and 2006/2007 images pair. Highest velocity is observed in middle part of the glacier while lowest in the accumulation zone ...

11 citations


Journal ArticleDOI
TL;DR: In this article, a more sophisticated pattern of the cold and temperate ice distribution within the glaciers than it was earlier known that should be taken into consideration when modeling and forecasting dynamics of the polythermal glaciers and investigating internal processes of the temperately ice formation in such glaciers.
Abstract: Data of ground-based radio-echo sounding of 16 glaciers located on the Nordenskiold Land, Spitsbergen, carried out in springs of 1999, 2007 and 2010–2013, allowed defining five glaciers as of the cold thermal type while other eleven ones were polythermal glaciers. In the last ones (polythermal) the average thickness of the upper layer of cold ice and the bottom layer of temperate ice was equal to 11-66 m and 15-96 m, respectively. The ratio of these thicknesses varies from 0.32 to 2.28, and the volume fraction of temperate ice in the total volume of the glaciers varies from 1 to 74% and changes from 0 to 50% in the ablation zone up to 80% in the accumulation zone. Thickness of cold ice was determined by measured delay time of radar reflections from cold-temperate surface (CTS) while thickness of temperate ice was derived as a difference between the total thickness of the glacier and the thickness of its cold ice. For interpretation of radar reflections from CTS we used the noticeable distinction in character of the radar reflections from the upper and lower thicknesses of glacier: absence of internal reflections (excluding reflections from buried crevasses and glacier wells) from upper cold ice layer and a great number of reflections of hyperbolic form from the lower layer related to strong scattering of radio waves by water inclusions in the temperate ice. According to the measurements, relative power of the radar reflections from CTS is by 5,5–14,2 dB smaller than those from the bedrock, that can be considered as an indicator of smaller water content at CTS; so, the repeated measurements of their relative power can be used for estimation of temporal changes in the water content at these boundaries. In layers of the temperate ice, the series of vertical hyperbolic reflections penetrating the cold ice down to CTS and further to the bedrock were detected. Such reflections are related to buried crevasses and/or the glacier wells and can serve as sources of the water permeating during the melt periods from the glacier surface down to CTS and bedrock and, thus, influencing on the ice viscosity and fluidity as well as on velocity of the bottom sliding in the polythermal glaciers. Repeated measurements of relative power of reflections from buried crevasses and wells can also be used to study processes of freezing them through and emptying during the period before start of the surface melting. Relation between volume of temperate ice and area of 16 studied glaciers was used to estimate the probability of existence of polythermal glaciers with a temperate ice core in all 202 glaciers in the Nordenskiold Land. 72 glaciers with areas exceeding 1.79 km2 may be referred to the polythermal type. The probable total volume of temperate ice in these glaciers amounts roughly to 10 km3, and with the 95% confidence it is within the interval from 8 to 33 km3. Almost 80% of the whole temperate ice may be concentrated in only five glaciers with area more than 17 km2, that makes up 2.5% of the total number of glaciers and about 30% of their total area. Data presented in this paper demonstrate more sophisticated pattern of the cold and temperate ice distribution within the glaciers than it was earlier known that should be taken into consideration when modeling and forecasting dynamics of the polythermal glaciers and investigating internal processes of the temperate ice formation in such glaciers.

8 citations


Journal ArticleDOI
TL;DR: The first report on the Psuedomonas sp.
Abstract: Glaciers are the cryospheric niches which support concealed microbial life. They inhabit broadspectrum culturable and non-culturable bacterial diversity. There is virtually very little information on the psychrophilic/psychrotolerant bacterial diversity found in the glaciers in India. Indian Himalayas are regarded as the world heritage of flora and fauna. As it houses many largest glaciers in its lap, a new venture into glaciers has been started. Microbiological investigation of the glaciers in North-East India will help us to have an insight into the hidden treasure of microflora. We are providing the first report on the Psuedomonas sp. diversity from Kanchengayao glacier, North Sikkim, India. It is one of the most dominant genera isolated from glacier ice samples. This genus is one of the most medically and ecologically important groups of Gamma-proteobacteria present in environment. In the present study, the diversity of Pseudomonas species isolated from ice core sample was carried out based on the phenotypic and genotypic analysis. It was found that the glacier was abundant in Pseudomonas azotoformans; Pseudomonas poae; Stenotrophomonas maltophilia; Pseudomonas fluorescens; Pseudomonas reactants; Pseudomonas hibiscicola and Pseudomonas synxantha. Interestingly, the antibiotic susceptibility test showed that all the isolates were resistant to Ampicillin (10mcg) but all were sensitive to Streptomycin (10mcg), 19 isolates were resistant to Vancomycin (30mcg) and six were resistant against Tetracycline (30mcg) whereas majority of the isolates showed intermediate response. The antibiotic resistance found in this unexplored area is an important study and first of its kind reported from this glacier.

6 citations


Proceedings ArticleDOI
01 Jul 2019
TL;DR: Assessment of the applicability of Sentinel-1 C-Band SAR data from its -1a and -1b platforms for estimating surface ice flow velocities in Indian Himalayan Region (IHR) suggests they provide a limited yet valuable opportunity to understand and model surface dynamics of mountain glaciers.
Abstract: Recent studies have revealed that variations in glacier movement over larger time scales can be explained by the changes in total mass of the glacier, making it an effective indicator of glacier health. It is vital to obtain precise and accurate glacier movement velocity to investigate the glacier health. Satellite based Differential SAR (Synthetic Aperture Radar) Interferometry (DInSAR) techniques have been used for continuous monitoring of glacier surface movements. However, it is still challenging to employ this method in mountainous regions, such as the Indian Himalaya, due to e.g. severe temporal decorrelation and rapid glacier changes, and complex geological situation. Thanks to a pool of freely available ESA’s Sentinel-1 C-Band SAR data with a short time repeat cycle, it is possible to overcome such challenges. This study attempts to assess the applicability of these datasets from its -1a and -1b platforms for estimating surface ice flow velocities in Indian Himalayan Region (IHR). Siachen Glacier, located in Karakoram range of IHR, is chosen as a representative glacier in this study, using which assessment of the dataset is performed and results are presented. 6-day interferometric pair was used for revealing the glacier velocity, estimated to range between 0m/y in some parts of the accumulation zone to 135m/y along the main trunk of the glacier in ablation zone. It is observed that, although datasets from Sentinel-1 mission are applicable for DInSAR processing in IHR, they provide a limited yet valuable opportunity to understand and model surface dynamics of mountain glaciers.

3 citations


Journal ArticleDOI
01 Jul 2019
TL;DR: In this paper, the chemical analysis of groundwater in Yurubcheno-Tokhomo hydrocarbon accumulation zone (YTHAZ) was carried out, which revealed that fresh, brackish, saline waters and brines of various chemical types occur in the study area.
Abstract: In this study the chemical analysis of groundwater in Yurubcheno-Tokhomo hydrocarbon accumulation zone (YTHAZ) was carried out. The analysis revealed that fresh, brackish, saline waters and brines of various chemical types occur in the study area. Water salinity increases with the depth, but this dependency is not observed in Vendian and Riphean oil and gas deposits. The most mineralized brines occur in the salt-bearing hydrogeological formation. On the basis of the data on the geochemistry of groundwater, the possibilities of their further practical application were determined.

1 citations


Proceedings ArticleDOI
01 Sep 2019
TL;DR: In this article, an acquisition campaign of the ONERA airborne synthetic aperture radar system RAMSES has been set up on the Greenland ice-shelf to assess the detectability of buried object and subsurface features through dry snow/ice cover.
Abstract: An acquisition campaign of the ONERA airborne synthetic aperture radar system RAMSES has been set up on the Greenland ice-shelf to assess the detectability of buried object and subsurface features through dry snow/ice cover. Three bands where investigated UHF, L and X band expecting a tradeoff between cover penetration and target radar cross-section, the latter being critical due to the expected high clutter radar cross-section. Four sites were imaged, a calibration zone and a front glacier close to Kangerlussuaq, a dry accumulation zone North of the polar circle, a percolated accumulation zone East of Narsassuaq, and an intermediate zone between accumulation and ablation zone. The engine fragment plume of an uncontained engine failure on a commercial jet-liner (about 190 days earlier) was in the middle of the percolated accumulation zone, providing several known buried fragments, as well as opportunities to unravel unknown buried fragments that may have an interest for the engine failure investigation. Test objects (corner reflectors, Luneburg lens, ice filed plastic sled, snow refilled hole) have been setup at known positions and depths to assess detection through cover and ice drift rates. Processing of the data confirmed the high clutter return, the better penetration at low (UHF) band and the higher radar cross-section at high (X) band. However, the setup targets radar cross-section presented an unexpected considerable attenuation that prompted the use of X-band and intensive processing to detect buried targets.

Proceedings ArticleDOI
01 Jul 2019
TL;DR: An acquisition campaign of the ONERA airborne synthetic aperture radar system RAMSES has been set up on the Greenland ice-shelf to assess the detectability of buried objects and subsurface feature through dry snow/ice cover, finding both UHF and X band are indeed providing complementing results.
Abstract: An acquisition campaign of the ONERA airborne synthetic aperture radar system RAMSES have been set up on the Greenland ice-shelf to assess the detectability of buried objects and subsurface feature through dry snow/ice cover. Three band were investigated UHF band, L band and X band, forecasting a better penetration at lower band, but an higher radar cross section for a given object/feature at higher band, thus a trade off for the optimal frequency band to use that was not clear prior to experiment.Three sites were imaged, one in the accumulation zone North of the polar circle (East of Kangerlussuaq airport), one in the accumulation zone in a warmer southern area (East of Narsassuaq airport) and one in the intermediate zone between accumulation and ablation zones (plus a calibration zone and a front glacier close to Kangerlussuaq).Processing of the data revealed that both UHF and X band are indeed providing complementing results (deeper bigger feature versus shallow smaller features), but intermediate L band combining both drawbacks of higher attenuation and lower features RCS did not seem to yield any further information.