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Modeling of groundwater flow at depth in crystalline rock beneath a moving ice-sheet margin, exemplified by the Fennoscandian Shield, Sweden | Modélisation de l’écoulement souterrain profond dans une roche cristalline à l’aplomb du front d’une calotte glaciaire en mouvement, exemple du Bouclier Fenno-scandien, Suède Modelado de flujo de agua subterránea en profundidad en rocas cristalinas del límite de una capa de hielo en movimiento, ejemplificado por el Escudo de Fennoscandian, Suecia 移动冰盖边缘下结晶岩深处地下水流模拟,以瑞典的芬诺斯堪的亚地盾为例 Modelação do fluxo subterrâneo em profundidade em rochas cristalinas sob a margem de um manto de gelo móvel, exemplificada pelo Escudo Fenoscandinavo, Suécia Texte intégral
2013
Vidstrand, Patrik | Follin, Sven | Selroos, Jan-Olof | Näslund, Jens-Ove | Rhén, Ingvar
On-going geological disposal programs for spent nuclear fuel have generated strong demands for investigation and characterization of deep-lying groundwater systems. Because of the long time scales for which radiological safety needs to be demonstrated in safety assessment applications, an analysis of the hydrogeological performance of the geosphere system during glacial climate conditions is needed. Groundwater flow at depth in crystalline rock during the passage of an ice-sheet margin is discussed based on performed groundwater-flow modeling of two bedrock sites, Forsmark and Laxemar, in the Fennoscandian Shield, Sweden. The modeled ice sheet mimics the Weichselian ice sheet during its last major advance and retreat over northern Europe. The paper elaborates and analyzes different choices of top boundary conditions at the ice sheet–subsurface interface (e.g. ice-sheet thickness and ice-margin velocity) and in the proglacial area (presence or lack of permafrost) and relates these choices to available groundwater-flow-model hydraulic output and prevailing conceptual hydrogeochemical models of the salinity evolution at the two sites. It is concluded that the choice of boundary conditions has a strong impact on results and that the studied sites behave differently for identical boundary conditions due to differences in their structural-hydraulic properties.
Afficher plus [+] Moins [-]Impacts of climate, lake size, and supra- and sub-permafrost groundwater flow on lake-talik evolution, Yukon Flats, Alaska (USA) | Impact du climat, de la dimension du lac, de l’écoulement de l’eau supra-et infra-pergélisol sur l’évolution d’un lac de talik, Yukon Flats, Alaska, USA Impactos del clima, tamaño del lago y flujo subterráneo del supra y sub permafrost en la evolución del talik de un lago, Yukon Flats, Alaska (EEUU) 气候、湖泊规模和永久冻土层上下的地下水流对阿拉斯加州育空平原(美国)湖泊-层间不冻层演化的影响 Impacto do clima, dimensão do lago e fluxo de água subterrânea acima e sob o permafrost na evolução da associação lago-talik, Yukon Flats, Alaska (EUA) Texte intégral
2013
Wellman, TristanP. | Voss, CliffordI. | Walvoord, MichelleA.
In cold regions, hydrologic systems possess seasonal and perennial ice-free zones (taliks) within areas of permafrost that control and are enhanced by groundwater flow. Simulation of talik development that follows lake formation in watersheds modeled after those in the Yukon Flats of interior Alaska (USA) provides insight on the coupled interaction between groundwater flow and ice distribution. The SUTRA groundwater simulator with freeze–thaw physics is used to examine the effect of climate, lake size, and lake–groundwater relations on talik formation. Considering a range of these factors, simulated times for a through-going sub-lake talik to form through 90 m of permafrost range from ∼200 to > 1,000 years (vertical thaw rates < 0.1–0.5 m yr⁻¹). Seasonal temperature cycles along lake margins impact supra-permafrost flow and late-stage cryologic processes. Warmer climate accelerates complete permafrost thaw and enhances seasonal flow within the supra-permafrost layer. Prior to open talik formation, sub-lake permafrost thaw is dominated by heat conduction. When hydraulic conditions induce upward or downward flow between the lake and sub-permafrost aquifer, thaw rates are greatly increased. The complexity of ground-ice and water-flow interplay, together with anticipated warming in the arctic, underscores the utility of coupled groundwater-energy transport models in evaluating hydrologic systems impacted by permafrost.
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