The Experts below are selected from a list of 25560 Experts worldwide ranked by ideXlab platform
Jt Bessette - One of the best experts on this subject based on the ideXlab platform.
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radar sounding characterization of the subglacial Groundwater Table beneath hiawatha glacier greenland
Geophysical Research Letters, 2021Co-Authors: Jt Bessette, Dm Schroeder, Thomas M Jordan, Joseph A MacgregorAbstract:Radar-sounding surveys associated with the discovery of a large impact crater beneath Hiawatha Glacier, Greenland, revealed bright, flat subglacial reflections hypothesized to originate from a subglacial Groundwater Table. We test this hypothesis using radiometric and hydrologic analysis of those radar data. The dielectric loss between the reflection from the top of the basal layer and subglacial reflection and their reflectivity difference represent dual constraints upon the complex permittivity of the basal material. Either ice-cemented debris or fractured, well-drained bedrock explain the basal layer's radiometric properties. The subglacial reflector's geometry is parallel to isopotential hydraulic head contours, located 7.5-15.3 m below the interface, and 11 ± 7 dB brighter than the ice-basal layer reflection. We conclude that this subglacial reflection is a Groundwater Table and that its detection was enabled by the wide bandwidth of the radar system and unusual geologic setting, suggesting a path for future direct radar detection of subglacial Groundwater elsewhere.
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Radar‐Sounding Characterization of the Subglacial Groundwater Table Beneath Hiawatha Glacier, Greenland
'American Geophysical Union (AGU)', 2021Co-Authors: Jt Bessette, Dm Schroeder, Tm Jordan, Ja MacgregorAbstract:Radar-sounding surveys associated with the discovery of a large impact crater beneath Hiawatha Glacier, Greenland, revealed bright, flat subglacial reflections hypothesized to originate from a subglacial Groundwater Table. We test this hypothesis using radiometric and hydrologic analysis of those radar data. The dielectric loss between the reflection from the top of the basal layer and subglacial reflection and their reflectivity difference represent dual constraints upon the complex permittivity of the basal material. Either ice-cemented debris or fractured, well-drained bedrock explain the basal layer's radiometric properties. The subglacial reflector's geometry is parallel to isopotential hydraulic head contours, located 7.5–15.3 m below the interface, and 11 ± 7 dB brighter than the ice–basal layer reflection. We conclude that this subglacial reflection is a Groundwater Table and that its detection was enabled by the wide bandwidth of the radar system and unusual geologic setting, suggesting a path for future direct radar detection of subglacial Groundwater elsewhere
Thomas M Jordan - One of the best experts on this subject based on the ideXlab platform.
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radar sounding characterization of the subglacial Groundwater Table beneath hiawatha glacier greenland
Geophysical Research Letters, 2021Co-Authors: Jt Bessette, Dm Schroeder, Thomas M Jordan, Joseph A MacgregorAbstract:Radar-sounding surveys associated with the discovery of a large impact crater beneath Hiawatha Glacier, Greenland, revealed bright, flat subglacial reflections hypothesized to originate from a subglacial Groundwater Table. We test this hypothesis using radiometric and hydrologic analysis of those radar data. The dielectric loss between the reflection from the top of the basal layer and subglacial reflection and their reflectivity difference represent dual constraints upon the complex permittivity of the basal material. Either ice-cemented debris or fractured, well-drained bedrock explain the basal layer's radiometric properties. The subglacial reflector's geometry is parallel to isopotential hydraulic head contours, located 7.5-15.3 m below the interface, and 11 ± 7 dB brighter than the ice-basal layer reflection. We conclude that this subglacial reflection is a Groundwater Table and that its detection was enabled by the wide bandwidth of the radar system and unusual geologic setting, suggesting a path for future direct radar detection of subglacial Groundwater elsewhere.
Joseph A Macgregor - One of the best experts on this subject based on the ideXlab platform.
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radar sounding characterization of the subglacial Groundwater Table beneath hiawatha glacier greenland
Geophysical Research Letters, 2021Co-Authors: Jt Bessette, Dm Schroeder, Thomas M Jordan, Joseph A MacgregorAbstract:Radar-sounding surveys associated with the discovery of a large impact crater beneath Hiawatha Glacier, Greenland, revealed bright, flat subglacial reflections hypothesized to originate from a subglacial Groundwater Table. We test this hypothesis using radiometric and hydrologic analysis of those radar data. The dielectric loss between the reflection from the top of the basal layer and subglacial reflection and their reflectivity difference represent dual constraints upon the complex permittivity of the basal material. Either ice-cemented debris or fractured, well-drained bedrock explain the basal layer's radiometric properties. The subglacial reflector's geometry is parallel to isopotential hydraulic head contours, located 7.5-15.3 m below the interface, and 11 ± 7 dB brighter than the ice-basal layer reflection. We conclude that this subglacial reflection is a Groundwater Table and that its detection was enabled by the wide bandwidth of the radar system and unusual geologic setting, suggesting a path for future direct radar detection of subglacial Groundwater elsewhere.
Wu Xiao - One of the best experts on this subject based on the ideXlab platform.
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effects of land use transitions due to underground coal mining on ecosystem services in high Groundwater Table areas a case study in the yanzhou coalfield
Land Use Policy, 2018Co-Authors: Wu Xiao, Tao WangAbstract:Abstract Coal resources play a strategic role in long-term development in China. However, underground mining activities in high Groundwater Table areas result in dramatic land use transition, putting both the ecosystem and the environment under great pressure. This paper examines the dynamic patterns of land use in high Groundwater coal basins (HGCBs) using high-resolution Landsat TM (Thematic Mapper) data from 1985, 1995, 2005, 2010, and 2015, and socio-economic data from research institutes and government departments, and assesses the changes of ecosystem service value (ESV) by drawing a connection between the observed land use dynamics and the evaluation of ESV, based on the latest research of Xie et al. (2015) and some revisions adapted to the situation in the mining areas. The outcomes indicated that from 1985 to 2005, the ESV of the study area had a sustained growth, from 308.66 million RMB¥ in 1985–481.50 million RMB¥ in 2005. However, this growth has since stopped and turned into a decrease, with ESV dropping to 334.27 million RMB¥ in 2015. The reasons for the changes in ESV were analyzed: the large transition of construction land and farmland to waterbody caused by mining subsidence and restoration activities play a positive role, while the urbanization process in mining areas leading to the expansion of cities, and drought for the past 5 years leading to the shrinkage of waterbody, bring negative efforts to ESV. Based on the analysis above, some of the major implications were discussed. It is argued that the mining-induced land use transition will continue in the near future in HGCBs. Therefore, in order to fully consider the future landscape and thus optimize land use and extend urban development space it is necessary: to make pre-subsidence plans to maximize the farmland and ensure food security; to restore the secondary waterbody; to protect regional ecosystem service function and maintain its stability; and to make urban planning on the basis of subsidence prediction at every stage. Only in this way can HGCBs realize the sustainable use of ecological resources, as well as the integration of economic, social and ecologic benefits.
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dynamic subsidence simulation and topsoil removal strategy in high Groundwater Table and underground coal mining area a case study in shandong province
International Journal of Mining Reclamation and Environment, 2014Co-Authors: Wu Xiao, Yoginder P Chugh, Yanling ZhaoAbstract:Coal mining in high Groundwater Table areas causes many environmental issues. In China, such regions have three unique and significant characteristics, (1) multiple coal seams; (2) thick coal seams and (3) high Groundwater, which lead to mine subsidence ponds. In the past, reclamation of disturbed land was carried out after subsidence stabilised. Such reclamation is a low-percentage of reclaimed farmland, and has high reclamation cost, difficult construction conditions, because of relatively flat terrain and the shortage of backfilling materials in flat topography. Therefore, salvaging the topsoil before it is submerged in water and reusing it while subsidence becomes sTable would be a good way to improve the reclamation efficiency. This paper considers a longwall panel in Shandong province as a case study. Dynamic mining subsidence was simulated using mining subsidence prediction software. To illustrate subsidence development and its effects on farmland, the ground was first divided into cell size of 40 ...
Dan Chen - One of the best experts on this subject based on the ideXlab platform.
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Effects of vadose zone on Groundwater Table fluctuations in unconfined aquifers
Journal of Hydrology, 2015Co-Authors: Jun Kong, Pei Xin, Guofen Hua, Zhaoyang Luo, Chengji Shen, Dan ChenAbstract:Summary Above a shallow unconfined aquifer, a considerable amount of water is stored in the vadose zone. Through water exchange with the underlying unconfined aquifer, the vadose zone affects the Groundwater Table dynamics and overall behavior of the aquifer. In this paper, we examine tide-induced Groundwater Table fluctuations in unconfined aquifers influenced by vadose zone of finite thickness. Under the condition of small aquifer thickness ( D ) compared with the Groundwater wavelength ( L ) (i.e., μ 2 = D / L 2 ≪ 1 ) and small boundary oscillation amplitude ( a ) (i.e., e = a / D ≪ 1 ) (where μ 2 and e are two parameters), an approximate analytical solution was derived to quantify systematically the vadose zone effects, with a particular consideration of capping by the ground surface, i.e., the upper boundary of the vadose zone. Depending on the extent to which the capillary rise is truncated by the ground surface, the vadose zone enhances the Groundwater Table fluctuations in an unconfined aquifer. However, the mean Groundwater Table height and exchange between surface water and Groundwater are reduced due to the presence of the vadose zone. These effects are intensified with increased capillary rise, but weakened as the vadose zone thickens. This study provides a criterion for assessing the importance of vadose zone in modulating the response of unconfined aquifers to low-frequency forcing oscillations such as tides.
