112 research outputs found
Effectiveness of Four Water-Bearing Zones of the Glacierized Basin in Meltwater Runoff Modeling
Meltwater runoff modeling from glacierized basins needs several input data, including total meltwater contributing area. This study utilizes optical remote sensing data to assess glacierized basins in the central Himalayas where snow and glaciers contribute substantially to the water resources. Result shows that there are four main water-bearing zones in the basin: (a) dry snow, (b) wet snow, (c) exposed glacial ice, and (d) debris-covered glacial ice, and it is possible to differentiate and map these zones and their spatio-temporal variations from satellite sensor data. These zones can then be incorporated in meltwater runoff modeling as separate entities because they behave differently and cannot be aggregated into a uniform body
Prevailing Weather Conditions During Summer Seasons Around Gangotri Glacier
Meteorological data collected near the snout of the Gangotri Glacier suggest that the study area receives less rainfall. The average seasonal rainfall is observed to be about 260 mm. The rainfall distribution does not show any monsoon impact. Amount of seasonal rainfall is highly variable (131.4-368.8 mm) from year to year, but, in general, August had the maximum rainfall. A verage daily maximum and minimum temperatures were 14.7 and 4.1°C respectively, whereas average mean temperature was 9.4°C. July was recorded as the warmest month. During daytime, wind speed was four times higher than that at night-time. The average daytime and night-time winds were 12.6 and 3.0 km/h respectively. Mean seasonal evaporation was 640.8 mm, which is high with respect to the high altitude. Average relative humidity and daily sunshine duration were also high throughout the melting season
Encyclopedia of Snow, Ice and Glaciers
The objective of this encyclopedia is to present the current state of scientific understanding of various aspects of earth’s cryosphere – snow, glaciers, ice caps, ice sheets, ice shelves, sea ice, river and lake ice, and permafrost – and their related interdisciplinary connections under one umbrella. Therefore, every effort has been made to provide a comprehensive coverage of cryosphere by including a broad array of topics, such as the atmospheric processes responsible for snow formation; snowfall observations; snow cover and snow surveys; transformation of snow to ice and changes in their properties; classification of ice and glaciers and their worldwide distribution; glaciation and ice ages; glacier dynamics; glacier surface and subsurface characteristics; geomorphic processes and landscape formation; hydrology and sedimentary systems; hydrochemical and isotopic properties; permafrost modeling; hazards caused by cryospheric changes; trends of glacier retreat on a global scale along with the impact of climate change; and many more quantitative estimates of various glacier parameters, such as degree-day, mass balance, extent and volume, and downwasting. Also included are articles on GPS application, and satellite image application in glaciology; GPR analysis; and sea level rise
Developing a Practice in Remote Sensing for Next-Generation Human Rights Researchers
Remote sensing is increasingly recognized as an important tool for documenting human rights abuses. When used alongside interviews, case studies, surveys, forensic science, and other well-established research methods in human rights and humanitarian practice, remotely sensed data can effectively geolocate and establish chronologies for mass graves, forced displacement, destruction of cultural heritage sites, and other violations. But as a highly technical field of science that relies on ever-changing technologies, remote sensing and geospatial analysis are not readily accessible for human rights and humanitarian practitioners. The community of practice grew out of innovative work by practitioners at NGOs and specialized inter-governmental such as UNITAR/UNOSAT.
Now, with the increasing demand by human rights NGOs for geospatial evidence, there is an urgent need to expand the community of practitioners who have training in the appropriate and responsible use of geospatial technologies for human rights research and documentation. One piece of this will be opportunities for training new practitioners, such as a multi-disciplinary curriculum that prepares students across human rights, law, sciences, and engineering for work in this field. Places for those students to learn, such as university research centers focused on remote sensing and human rights, and experiential learning opportunities with NGOs also need to be created. These practitioners will then need places to do their work in NGOs, inter-governmental organizations, and development agencies.
After a brief introduction to the current state of practice and a pilot initiative at the University of Dayton, most of the session will be a facilitated discussion among session participants. What would a career pathway as a geospatial analyst for human rights look like? What educational opportunities are needed to support those careers? What experiential learning opportunities are available with human rights and humanitarian organizations? What is the role of funders and donors in developing this community of practice
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Mass Loss From Calving in Himalayan Proglacial Lakes
The formation and expansion of Himalayan glacial lakes has implications for glacier dynamics, mass balance and glacial lake outburst floods (GLOFs). Subaerial and subaqueous calving is an important component of glacier mass loss but they have been difficult to track due to spatiotemporal resolution limitations in remote sensing data and few field observations. In this study, we used near-daily 3 m resolution PlanetScope imagery in conjunction with an uncrewed aerial vehicle (UAV) survey to quantify calving events and derive an empirical area–volume relationship to estimate calved glacier volume from planimetric iceberg areas. A calving event at Thulagi Glacier in 2017 was observed by satellite from before and during the event to nearly complete melting of the icebergs, and was observed in situ midway through the melting period, thus giving insights into the melting processes. In situ measurements of Thulagi Lake’s surface and water column indicate that daytime sunlight absorption heats mainly just the top metre of water, but this heat is efficiently mixed downwards through the top tens of metres due to forced convection by wind-blown icebergs; this heat then is retained by the lake and is available to melt the icebergs. Using satellite data, we assess seasonal glacier velocities, lake thermal regime and glacier surface elevation change for Thulagi, Lower Barun and Lhotse Shar glaciers and their associated lakes. The data reveal widely varying trends, likely signifying divergent future evolution. Glacier velocities derived from 1960/70s declassified Corona satellite imagery revealed evidence of glacier deceleration for Thulagi and Lhotse Shar glaciers, but acceleration at Lower Barun Glacier following lake development. We used published modelled ice thickness data to show that upon reaching their maximum extents, Imja, Lower Barun and Thulagi lakes will contain, respectively, about 90 × 106 , 62 × 106 and 5 × 106 m3 of additional water compared to their 2018 volumes. Understanding lake–glacier interactions is essential to predict future glacier mass loss, lake formation and associated hazards
GlacierNet2: A Hybrid Multi-Model Learning Architecture for Alpine Glacier Mapping
In recent decades, climate change has significantly affected glacier
dynamics, resulting in mass loss and an increased risk of glacier-related
hazards including supraglacial and proglacial lake development, as well as
catastrophic outburst flooding. Rapidly changing conditions dictate the need
for continuous and detailed observations and analysis of climate-glacier
dynamics. Thematic and quantitative information regarding glacier geometry is
fundamental for understanding climate forcing and the sensitivity of glaciers
to climate change, however, accurately mapping debris-cover glaciers (DCGs) is
notoriously difficult based upon the use of spectral information and
conventional machine-learning techniques. The objective of this research is to
improve upon an earlier proposed deep-learning-based approach, GlacierNet,
which was developed to exploit a convolutional neural-network segmentation
model to accurately outline regional DCG ablation zones. Specifically, we
developed an enhanced GlacierNet2 architecture thatincorporates multiple
models, automatic post-processing, and basin-level hydrological flow techniques
to improve the mapping of DCGs such that it includes both the ablation and
accumulation zones. Experimental evaluations demonstrate that GlacierNet2
improves the estimation of the ablation zone and allows a high level of
intersection over union (IOU: 0.8839) score. The proposed architecture provides
complete glacier (both accumulation and ablation zone) outlines at regional
scales, with an overall IOU score of 0.8619. This is a crucial first step in
automating complete glacier mapping that can be used for accurate glacier
modeling or mass-balance analysis
Future glacial lake outburst flood (GLOF) hazard of the South Lhonak Lake, Sikkim Himalaya
The Teesta basin in Sikkim Himalaya hosts numerous glacial lakes in the high altitude glacierized region, including one of the largest and the fastest-growing South Lhonak Lake. While these lakes are mainly located in remote and unsettled mountain valleys, far-reaching glacial lake outburst floods (GLOFs) may claim lives and damage assets up to tens of kilometers downstream. Therefore, evaluating GLOF hazard associated with current and potential future glacier-retreat-driven changes is of high importance. In this work, we assess the future GLOF hazard of the South Lhonak Lake by integrating glacier and hydrodynamic modeling to calculate the lake's future volume and hydraulic GLOF characteristics and impacts along the valley. We identify the increased susceptibility of the lake to potential avalanche impacts as the lake grows in the future. Here we model six avalanche scenarios of varying magnitudes to evaluate the impact-wave generated in the lake and overtopping flow at the dam. Avalanche simulations indicate that the frontal moraine is susceptible to overtopping. The overtopping flow hydraulics is evaluated along the channel assuming no erosion of the moraine. Further, we consider three lake-breach scenarios to model GLOFs originating from the lake, flow propagation, and its downstream impacts. The uncertainty in the breach parameters including breach width and time of failure are calculated to estimate the upper and the lower hydraulic limits of potential future GLOF events. Further, the uncertainty in the flow hydraulics was evaluated using dynamic flood routing of six GLOFs that originate from the lake. Hydrodynamic GLOF modeling resulted in a predicted peak discharge of 4311 m3s−1, 8000 m3s−1, and 12,487 m3s−1 for breach depths of 20 m, 30 m, and 40 m respectively. The large-potential scenario suggests that maximum flow depth and flow velocity at Chungthang, a town proximally located to a major hydropower station built-in 2015, could reach up to 25–30 m and 6–9 m s−1, respectively. Mapping infrastructure exposed to GLOFs in the Teesta valley shows that many settlements and assets located along the river channel at Chungthang are potentially exposed to future GLOFs, indicating the need to conduct a full environmental impact assessment and potentially undertake GLOF risk mitigation measures
Mass movement hazard and exposure in the Himalaya
Himalaya is experiencing frequent catastrophic mass movement events such as avalanches and landslides, causing loss of human lives and infrastructure. Millions of people reside in critical zones potentially exposed to such catastrophes. Despite this, a comprehensive assessment of mass movement exposure is lacking at a regional scale. Here, we developed a novel method of determining mass movement trajectories and applied it to the Himalayan Mountain ranges for the first time to quantify the exposure of infrastructure, waterways, roadways, and population in six mountain ranges, including Hindu Kush, Karakoram, western Himalaya, eastern Himalaya, central Himalaya, and Hengduan Shan. Our results reveal that the exposure of buildings and roadways to mass movements is highest in Karakoram, whereas central Himalaya has the highest exposed waterways. The hotspots of exposed roadways are concentrated in Nepal, the North Indian states of Uttarakhand, Himachal Pradesh, the Union Territory of Ladakh, and China's Sichuan Province. Our analysis shows that the population in the central Himalaya is currently at the highest exposure to mass movement impacts. Projected future populations based on Shared Socio‐economic and Representative Concentration Pathways suggest that changing settlement patterns and emission scenarios will significantly influence the potential impact of these events on the human population. Assessment of anticipated secondary hazards (glacial lake outburst floods) shows an increase in probable headward impacts of mass movements on glacial lakes in the future. Our findings will support researchers, policymakers, stakeholders, and local governments in identifying critical areas that require detailed investigation for risk reduction and mitigation
Theoretical Foundations of Remote Sensing for Glacier Assessment and Mapping
The international scientific community is actively engaged in assessing ice sheet and alpine glacier fluctuations at a variety of scales. The availability of stereoscopic, multitemporal, and multispectral satellite imagery from the optical wavelength regions of the electromagnetic spectrum has greatly increased our ability to assess glaciological conditions and map the cryosphere. There are, however, important issues and limitations associated with accurate satellite information extraction and mapping, as well as new opportunities for assessment and mapping that are all rooted in understanding the fundamentals of the radiation transfer cascade. We address the primary radiation transfer components, relate them to glacier dynamics and mapping, and summarize the analytical approaches that permit transformation of spectral variation into thematic and quantitative parameters. We also discuss the integration of satellite-derived information into numerical modeling approaches to facilitate understandings of glacier dynamics and causal mechanisms
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