| 1. |
- Kumar, Rajesh, et al.
(författare)
-
Development of a Glacio-hydrological Model for Discharge and Mass Balance Reconstruction
- 2016
-
Ingår i: Water resources management. - : Springer Science and Business Media LLC. - 0920-4741 .- 1573-1650. ; 30:10, s. 3475-3492
-
Tidskriftsartikel (refereegranskat)abstract
- The reconstruction of glacio-hydrological records for the data deficient Himalayan catchments is needed in order to study the past and future water availability. The study provides outcomes of a glacio-hydrological model based on the degree-day approach. The model simulates the discharge and mass balance for glacierised Shaune Garang catchment. The degree-day factors for different land covers, used in the model, were estimated using daily stake measurements on Shaune Garang glacier and they were found to be varying between 2.6 ± 0.4 and 9.3 ± 0.3 mm °C−1day−1. The model is validated using observed discharge during ablation season of 2014 with coefficient of determination (R2) 0.90 and root mean square error (RMSE) 1.05 m3 sec−1. The model is used to simulate discharge from 1985 to 2008 and mass balance from 2001 to 2008. The model results show significant contribution of seasonal snow and ice melt in total discharge of the catchment, especially during summer. We observe the maximum discharge in July having maximum contribution from snow and ice melt. The annual melt season discharge shows following a decreasing trend in the simulation period. The reconstructed mass balance shows mass loss of 0.89 m we per year between 2001 and 2008 with slight mass gain during 2000/01 and 2004/05 hydrological years.
|
|
| 2. |
- Bhardwaj, Anshuman, et al.
(författare)
-
A lake detection algorithm (LDA) using Landsat 8 data : A comparative approach in glacial environment
- 2015
-
Ingår i: International Journal of Applied Earth Observation and Geoinformation. - : Elsevier BV. - 1569-8432 .- 1872-826X. ; 38, s. 150-163
-
Tidskriftsartikel (refereegranskat)abstract
- Glacial lakes show a wide range of turbidity. Owing to this, the normalized difference water indices (NDWIs) as proposed by many researchers, do not give appropriate results in case of glacial lakes. In addition, the sub-pixel proportion of water and use of different optical band combinations are also reported to produce varying results. In the wake of the changing climate and increasing GLOFs (glacial lake outburst floods), there is a need to utilize wide optical and thermal capabilities of Landsat 8 data for the automated detection of glacial lakes. In the present study, the optical and thermal bandwidths of Landsat 8 data were explored along with the terrain slope parameter derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model Version2 (ASTER GDEM V2), for detecting and mapping glacial lakes. The validation of the algorithm was performed using manually digitized and subsequently field corrected lake boundaries. The pre-existing NDWIs were also evaluated to determine the supremacy and the stability of the proposed algorithm for glacial lake detection. Two new parameters, LDI (lake detection index) and LF (lake fraction) were proposed to comment on the performances of the indices. The lake detection algorithm (LDA) performed best in case of both, mixed lake pixels and pure lake pixels with no false detections (LDI = 0.98) and very less areal underestimation (LF= 0.73). The coefficient of determination (R-2) between areal extents of lake pixels, extracted using the LDA and the actual lake area, was very high (0.99). With understanding of the terrain conditions and slight threshold adjustments, this work can be replicated for any mountainous region of the world.
|
|
| 3. |
- Bhardwaj, Anshuman, et al.
(författare)
-
Applicability of Landsat 8 data for characterizing glacier facies and supraglacial debris
- 2015
-
Ingår i: International Journal of Applied Earth Observation and Geoinformation. - : Elsevier BV. - 1569-8432 .- 1872-826X. ; 38, s. 51-64
-
Tidskriftsartikel (refereegranskat)abstract
- present work evaluates the applicability of operational land imager (OLI) and thermal infrared sensor (TIRS) on-board Landsat 8 satellite. We demonstrate an algorithm for automated mapping of glacier facies and supraglacial debris using data collected in blue, near infrared (NIR), short wave infrared (SWIR) and thermal infrared (TIR) bands. The reflectance properties invisible and NIR regions of OLI for various glacier facies are in contrast with those in SWIR region. Based on the premise that different surface types (snow, ice and debris) of a glacier should show distinct thermal regimes, the 'at-satellite brightness temperature' obtained using TIRS was used as a base layer for developing the algorithm. This base layer was enhanced and modified using contrasting reflectance properties of OLI bands. In addition to fades and debris cover characterization, another interesting outcome of this algorithm was extraction of crevasses on the glacier surface which were distinctly visible in output and classified images. The validity of this algorithm was checked using field data along a transect of the glacier acquired during the satellite pass over the study area. With slight scene-dependent threshold adjustments, this work can be replicated for mapping glacier facies and supraglacial debris in any alpine valley glacier
|
|
| 4. |
- Bhardwaj, Anshuman, et al.
(författare)
-
MODIS-based estimates of strong snow surface temperature anomaly related to high altitude earthquakes of 2015
- 2017
-
Ingår i: Remote Sensing of Environment. - : Elsevier. - 0034-4257 .- 1879-0704. ; 188, s. 1-8
-
Tidskriftsartikel (refereegranskat)abstract
- The high levels of uncertainty associated with earthquake prediction render earthquakes some of the worst natural calamities. Here, we present our observations of MODerate resolution Imaging Spectroradiometer (MODIS)-derived Land Surface Temperature (LST) anomaly for earthquakes in the largest tectonically active Himalayan and Andean mountain belts. We report the appearance of fairly detectable pre-earthquake Snow Surface Temperature (SST) anomalies. We use 16 years (2000–2015) of MODIS LST time-series data to robustly conclude our findings for three of the most destructive earthquakes that occurred in 2015 in the high mountains of Nepal, Chile, and Afghanistan. We propose the physical basis behind higher sensitivity of snow towards geothermal emissions. Although the preliminary appearance of SST anomalies and their amplitudes vary, we propose employing a global-scale monitoring system for detecting and studying such spatio-temporal geophysical signals. With the advent of improved remote sensors, we anticipate that such efforts can be another step towards improved earthquake predictions.
|
|
| 5. |
- Kumar, Rajesh, et al.
(författare)
-
Dynamics of suspended sediment load with respect to summer discharge and temperatures in Shaune Garang glacierized catchment, Western Himalaya
- 2018
-
Ingår i: Acta Geophysica. - : Springer. - 1895-6572 .- 1895-7455. ; 66:5, s. 1109-1120
-
Tidskriftsartikel (refereegranskat)abstract
- The observed and predicted rise in temperature will have deleterious impact on melting of snow and ice and form of precipitation which is already evident in Indian Himalayan Region. The temperature-dependent entities like discharge and sediment load will also vary with the observed and predicted rise posing environmental, social and economic threat in the region. There is little known about sediment load transport in relation to temperature and discharge in glacierized catchments in Himalaya mainly due to the scarcity of ground-based observation. The present study is an attempt to understand the suspended sediment load and transportation in relation to variation in discharge and temperature in the Shaune Garang catchment. The result shows strong dependence of sediment concentration primarily on discharge (R2 = 0.84) and then on temperature (R2 = 0.79). The catchments with similar geological and climate setting were observed to have comparatively close weathering rate. The sediment load was found to be higher in the catchments in eastern and central part of Indian Himalayan Region in comparison with western part due to dominance of Indian Summer Monsoon leading to high discharge. The annual physical weathering rate in Shaune Garang catchment was found to be 411 t km−2 year−1 which has increased from 327 t km−2 year−1 in around three decades due to rise in temperature causing increase in discharge and proportion of debris-covered glacierized area.
|
|
| 6. |
- Kumar, Ramesh, et al.
(författare)
-
Hydro-geochemical analysis of meltwater draining from Bilare Banga glacier, Western Himalaya
- 2019
-
Ingår i: Acta Geophysica. - : Springer. - 1895-6572 .- 1895-7455. ; 67:2, s. 651-660
-
Tidskriftsartikel (refereegranskat)abstract
- The changing climate is affecting the melting process of glacier ice and snow in Himalaya and may influence the hydro-geochemistry of the glacial meltwater. This paper represents the ionic composition of discharge from Bilare Banga glacier by carrying out hydro-geochemical analysis of water samples of melting season of 2017. The pH and EC were measured on-site in field, and others parameters were examined in the laboratory. The abundance of the ions observed in meltwater has been arranged in decreasing order for cations as Ca2+ > Mg2+ > Na+ > K+ and for anions as HCO3− > SO42− > Cl− > NO3−, respectively. Analysis suggests that the meltwater is mostly dominated by Ca2+ and HCO3−. It has been observed that the ionic concentration HCO3− is dominant and Cl− is the least in the catchment. Piper plot analysis suggests that the chemical composition of the glacier discharge not only has natural origin but also has some anthropogenic input. Hydro-geochemical heterogeneity reflected the carbonate-dominated features (Ca2+–HCO3−) in the catchment. The carbonate weathering was found as the regulatory factor to control the chemistry of the glacial meltwater due to the high enrichment ratio of (Ca2+ + Mg2+) against TZ+ and (Na+ + K+). In statistical approach, PCA analysis suggests that geogenic weathering dynamics in the catchment is associated with carbonate-dominant lithology.
|
|
| 7. |
- Kumar, Rajesh, et al.
(författare)
-
Hydro-geochemical characteristics of glacial meltwater from Naradu Glacier catchment, Western Himalaya
- 2019
-
Ingår i: Environmental Earth Sciences. - : Springer. - 1866-6280 .- 1866-6299. ; 78:24
-
Tidskriftsartikel (refereegranskat)abstract
- The pattern of changing hydro-geochemical characteristics of water in Himalayan rivers is primarily controlled by sediment load from natural sources in higher altitudes and anthropogenic sources such as the burning of fossil fuels for domestic use, vehicular emissions, and wind transported industrial pollutants in the downstream region. The assessment of water quality is critical for the comparison of natural and anthropogenic sources in the downstream areas due to the dependence of the population on the glacial meltwater for freshwater supply. In the present study, we investigate the physical and ionic characteristics of glacial meltwater from Naradu Glacier catchment concerning the dominant weathering process. The freshwater samples were collected during the ablation period of 2016 and 2017 from specified locations. The physical parameters (pH, electrical conductivity, and temperature) were measured in the field while the analyses for concentrations of major cations (Ca2+, Mg2+, K+, Na+) and major anions (Cl−, SO42−, HCO3−, NO3−) were done in the laboratory. The anions (HCO3− > SO42− > Cl− > NO3−) and cations (Ca2+ > Mg2+ > Na+ > K+) concentrations were observed to have similar trends for both of the ablation period. The statistical analysis shows the predominance of geological weathering processes in the catchment as the controlling factor for the variation in concentration of different ionic species. The catchment was found to be rich in rocks with carbonate mineral making the Ca2+ and HCO3− the most dominant ions in the glacial meltwater.
|
|
| 8. |
- Singh, Shaktiman, et al.
(författare)
-
Changing climate and glacio-hydrology: a case study of Shaune Garang basin, Himachal Pradesh
- 2018
-
Ingår i: International Journal of Hydrology Science and Technology. - : InderScience Publishers. - 2042-7808 .- 2042-7816. ; 8:3, s. 258-272
-
Tidskriftsartikel (refereegranskat)abstract
- The rise in temperature is already evident in Himalaya with rate of increase varying seasonally and spatially. Changes in precipitation are also evident with no clear trend. Several studies in different parts of Himalayas suggest that the glaciers are retreating in general with few exceptions as response to changes in temperature and precipitation. The stream flow in river basins in Indian Himalayan region (IHR) is already showing changes in studies undertaken in the last few decades. Use of glacio-hydrological models gives opportunity to estimate stream flow in glaciated river basins and understand the changes. The present study deals with estimation of discharge in Shaune Garang Basin, Himachal Pradesh using a glacio-hydrological model based on degree day factors. The model was used to estimate long term average of melt season discharge (1985-2007) in the basin. The modelled discharge shows good correlation with measured discharge for simulation period except for first year of comparison.
|
|
| 9. |
- Singh, Shaktiman, et al.
(författare)
-
Changing climate and glacio-hydrology in Indian Himalayan Region : a review
- 2016
-
Ingår i: Wiley Interdisciplinary Reviews. - : Wiley. - 1757-7780 .- 1757-7799. ; 7:3, s. 393-410
-
Tidskriftsartikel (refereegranskat)abstract
- This study presents a comprehensive review of the published literature on the evidences of a changing climate in the Indian Himalayan Region (IHR) and its impacts on the glacio-hydrology of the region. The IHR serves as an important source of fresh water for the densely populated areas downstream. It is evident from the available studies that temperature is significantly increasing in all parts of the IHR, whereas precipitation is not indicative of any particular spatiotemporal trend. Glacio-hydrological proxies for changing climate, such as, terminus and areal changes of the glaciers, glacier mass balance, and streamflow in downstream areas, highlight changes more evidently in recent decades. On an average, studies have predicted an increase in temperature and precipitation in the region, along with increase in streamflow of major rivers. Such trends are already apparent in some sub-basins of the western IHR. The region is particularly vulnerable to changing climate as it is highly dependent on snow and glacier melt run-off to meet its freshwater demands. We present a systematic review of key papers dealing with changing temperature, precipitation, glaciers, and streamflow in the IHR. We discuss these interdisciplinary themes in relation to each other, in order to establish the present and future impacts of climatic, glaciological, and hydrological changes in the region.
|
|
| 10. |
- Singh, Shaktiman, et al.
(författare)
-
Quantifying the Congruence between Air and Land Surface Temperatures for Various Climatic and Elevation Zones of Western Himalaya
- 2019
-
Ingår i: Remote Sensing. - : MDPI. - 2072-4292. ; 11:24
-
Tidskriftsartikel (refereegranskat)abstract
- The surface and near-surface air temperature observations are primary data for glacio-hydro-climatological studies. The in situ air temperature (Ta) observations require intense logistic and financial investments, making it sparse and fragmented particularly in remote and extreme environments. The temperatures in Himalaya are controlled by a complex system driven by topography, seasons, and cryosphere which further makes it difficult to record or predict its spatial heterogeneity. In this regard, finding a way to fill the observational spatiotemporal gaps in data becomes more crucial. Here, we show the comparison of Ta recorded at 11 high altitude stations in Western Himalaya with their respective land surface temperatures (Ts) recorded by Moderate Resolution Imagining Spectroradiometer (MODIS) Aqua and Terra satellites in cloud-free conditions. We found remarkable seasonal and spatial trends in the Ta vs. Ts relationship: (i) Ts are strongly correlated with Ta (R2 = 0.77, root mean square difference (RMSD) = 5.9 °C, n = 11,101 at daily scale and R2 = 0.80, RMSD = 5.7 °C, n = 3552 at 8-day scale); (ii) in general, the RMSD is lower for the winter months in comparison to summer months for all the stations, (iii) the RMSD is directly proportional to the elevations; (iv) the RMSD is inversely proportional to the annual precipitation. Our results demonstrate the statistically strong and previously unreported Ta vs. Ts relationship and spatial and seasonal variations in its intensity at daily resolution for the Western Himalaya. We anticipate that our results will provide the scientists in Himalaya or similar data-deficient extreme environments with an option to use freely available remotely observed Ts products in their models to fill-up the spatiotemporal data gaps related to in situ monitoring at daily resolution. Substituting Ta by Ts as input in various geophysical models can even improve the model accuracy as using spatially continuous satellite derived Ts in place of discrete in situ Ta extrapolated to different elevations using a constant lapse rate can provide more realistic estimates.
|
|
| 11. |
|
|
| 12. |
- Bhardwaj, Anshuman, et al.
(författare)
-
A review on remotely sensed land surface temperature anomaly as an earthquake precursor
- 2017
-
Ingår i: International Journal of Applied Earth Observation and Geoinformation. - : Elsevier. - 1569-8432 .- 1872-826X. ; 63, s. 158-166
-
Tidskriftsartikel (refereegranskat)abstract
- The low predictability of earthquakes and the high uncertainty associated with their forecasts make earthquakes one of the worst natural calamities, capable of causing instant loss of life and property. Here, we discuss the studies reporting the observed anomalies in the satellite-derived Land Surface Temperature (LST) before an earthquake. We compile the conclusions of these studies and evaluate the use of remotely sensed LST anomalies as precursors of earthquakes. The arrival times and the amplitudes of the anomalies vary widely, thus making it difficult to consider them as universal markers to issue earthquake warnings. Based on the randomness in the observations of these precursors, we support employing a global-scale monitoring system to detect statistically robust anomalous geophysical signals prior to earthquakes before considering them as definite precursors.
|
|
| 13. |
- Bhardwaj, Anshuman, et al.
(författare)
-
Automated detection and temporal monitoring of crevasses using remote sensing and their implications for glacier dynamics
- 2016
-
Ingår i: Annals of Glaciology. - 0260-3055 .- 1727-5644. ; 57:71, s. 81-91
-
Tidskriftsartikel (refereegranskat)abstract
- Detailed studies on temporal changes of crevasses and their linkage with glacier dynamics are scarce in the Himalayan context. Observations of temporally changing surficial crevasse patterns and their orientations are suggestive of the processes that determine seasonal glacier flow characteristics. In the present study, on a Himalayan valley glacier, changing crevasse patterns and orientations were detected and mapped on Landsat 8 images in an automated procedure using the ratio of Thermal Infrared Sensor (TIRS) band 10 to Optical Land Imager (OLI) shortwave infrared (SWIR) band 6. The ratio was capable of mapping even crevasses falling under mountain shadows. Differential GPS observations suggested an average error of 3.65% and root-mean-square error of 6.32m in crevasse lengths. A year-round observation of these crevasses, coupled with field-based surface velocity measurements, provided some interesting interpretations of seasonal glacier dynamics.
|
|
| 14. |
- Sam, Lydia, et al.
(författare)
-
Remote sensing flow velocity of debris-covered glaciers using Landsat 8 data
- 2016
-
Ingår i: Progress in physical geography. - : SAGE Publications. - 0309-1333 .- 1477-0296. ; 40:2, s. 305-321
-
Tidskriftsartikel (refereegranskat)abstract
- Changes in ice velocity of a glacier regulate its mass balance and dynamics. The estimation of glacier flow velocity is therefore an important aspect of temporal glacier monitoring. The utilisation of conventional ground-based techniques for detecting glacier surface flow velocity in the rugged and alpine Himalayan terrain is extremely difficult. Remote sensing-based techniques can provide such observations on a regular basis for a large geographical area. Obtaining freely available high quality remote sensing data for the Himalayan regions is challenging. In the present work, we adopted a differential band composite approach, for the first time, in order to estimate glacier surface velocity for non-debris and supraglacial debris covered areas of a glacier, separately. We employed various bandwidths of the Landsat 8 data for velocity estimation using the COSI-Corr (co-registration of optically sensed images and correlation) tool. We performed the accuracy assessment with respect to field measurements for two glaciers in the Indian Himalaya. The panchromatic band worked best for non-debris parts of the glaciers while band 6 (SWIR – short wave infrared) performed best in case of debris cover. We correlated six temporal Landsat 8 scenes in order to ensure the performance of the proposed algorithm on monthly as well as yearly timescales. We identified sources of error and generated a final velocity map along with the flow lines. Over- and underestimates of the yearly glacier velocity were found to be more in the case of slow moving areas with annual displacements less than 5 m. Landsat 8 has great capabilities for such velocity estimation work for a large geographic extent because of its global coverage, improved spectral and radiometric resolutions, free availability and considerable revisit time.
|
|
| 15. |
- Sam, Lydia, et al.
(författare)
-
Small Lava Caves as Possible Exploratory Targets on Mars : Analogies Drawn from UAV Imaging of an Icelandic Lava Field
- 2020
-
Ingår i: Remote Sensing. - : MDPI. - 2072-4292. ; 12:12
-
Tidskriftsartikel (refereegranskat)abstract
- Volcanic-aeolian interactions and processes have played a vital role in landscape evolution on Mars. Martian lava fields and associated caves have extensive geomorphological, astrobiological, and in-situ resource utilization (ISRU) implications for future Mars missions which might be focused on subsurface exploration. Although several possible cave “skylights” of tens to >100 m diameter have been spotted in lava fields of Mars, there is a possibility of prevalence of meter-scale features which are an order of magnitude smaller and difficult to identify but could have vital significance from the scientific and future exploration perspectives. The Icelandic volcanic-aeolian environment and fissure volcanoes can serve as analogs to study lava flow-related small caves such as surface tubes, inflationary caves, liftup caves, and conduits. In the present work, we have tried to explore the usability of unmanned aerial vehicle (UAV)-derived images for characterizing a solidified lava flow and designing a sequential methodology to identify small caves in the lava flow. In the mapped area of ~0.33 km2, we were able to identify 81 small cave openings, five lava flow morphologies, and five small cave types using 2 cm/pixel high-resolution images. The results display the usefulness of UAV imaging for such analogous research, and also highlight the possibility of the widespread presence of similar small cave openings in Martian lava fields. Such small openings can facilitate optimal air circulation within the caves while sheltering the insides from physical weathering and harmful radiations. Using the available best resolution remote sensing images, we extend the analogy through the contextual and geomorphological analysis of several possible pit craters in the Tharsis region of Mars, in a region of extremely vesicular and fragile lava crust with pahoehoe-type morphology. We report two possible pit craters in this region, with diameters as small as ~20 m. The possibility that such small cave openings can lead to vast subterranean hollow spaces on Mars cannot be ruled out considering its low gravity.
|
|
| 16. |
- Shekhar, Mayank, et al.
(författare)
-
Himalayan glaciers experienced significant mass loss during later phases of little ice age
- 2017
-
Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- To date, there is a gap in the data about the state and mass balance of glaciers in the climate-sensitive subtropical regions during the Little Ice Age (LIA). Here, based on an unprecedented tree-ring sampling coverage, we present the longest reconstructed mass balance record for the Western Himalayan glaciers, dating to 1615. Our results confirm that the later phase of LIA was substantially briefer and weaker in the Himalaya than in the Arctic and subarctic regions. Furthermore, analysis of the time-series of the mass-balance against other time-series shows clear evidence of the existence of (i) a significant glacial decay and a significantly weaker magnitude of glaciation during the latter half of the LIA; (ii) a weak regional mass balance dependence on either the El Niño-Southern Oscillation (ENSO) or the Total Solar Irradiance (TSI) taken in isolation, but a considerable combined influence of both of them during the LIA; and (iii) in addition to anthropogenic climate change, the strong effect from the increased yearly concurrence of extremely high TSI with El Niño over the past five decades, resulting in severe glacial mass loss. The generated mass balance time-series can serve as a source of reliable reconstructed data to the scientific community.
|
|
