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Parameter sensitivity analysis of a two-dimensional cryo-hydrogeological numerical model of degrading permafrost near Umiujaq (Nunavik, Canada)
Hydrogeology Journal ( IF 2.8 ) Pub Date : 2020-02-22 , DOI: 10.1007/s10040-020-02112-2
Britt M. C. Albers , John W. Molson , Victor F. Bense

A calibrated field-scale numerical model of groundwater flow and permafrost degradation has been used in a sensitivity analysis of permafrost thaw on thermal and hydraulic parameters. The two-dimensional cryo-hydrogeological model was developed using the HEATFLOW-SMOKER code applied to the Umiujaq field site in Nunavik, Quebec, Canada, and includes coupled groundwater flow and advective–conductive heat transport with latent-heat and temperature-dependent thermal and hydraulic properties. Model sensitivity was evaluated by using the PEST code to systematically vary selected thermal and hydraulic parameters, and was quantified with respect to three system output variables or ‘targets’: subsurface temperature, groundwater velocity and ground-surface heat flux. PEST-derived model sensitivities were similar for all targets which contained subsurface temperature profiles, while sensitivities were slightly higher when only summer conditions were considered as the target compared to a full year of data. This trend was attributed to greater heat exchange at the ground surface during the summer months, leading to a more active groundwater flow system and greater feedback to the thermal regime. For all targets, the hydraulic and thermal parameters of the shallow layers (fine sand and marine silt, respectively) as well as the parameters defining the ground-surface heat exchange layer, were more sensitive compared to the deeper layers (coarse sand and gravel, and unfractured bedrock). Sensitivities were also among the highest for the ground-surface heat flux target. High model sensitivity to these parameters highlights the importance of detailed site characterization in the near-surface zone for more realistic simulations of permafrost dynamics.



中文翻译:

Umiujaq(加拿大努纳维克)附近降解多年冻土的二维低温水文地质数值模型的参数敏感性分析

在多年冻土融化对热力和水力参数的敏感性分析中,使用了经过校准的地下水流量和多年冻土退化的现场规模数值模型。使用适用于加拿大魁北克省努纳维克的Umiujaq油田现场的HEATFLOW-SMOKER代码开发了二维低温水文地质模型,该模型包括耦合的地下水流和对流-传导热传输,以及潜热和温度相关的热能和热能。液压性能。通过使用PEST代码来系统地改变选定的热力和水力参数来评估模型敏感性,并根据三个系统输出变量或“目标”对模型敏感性进行了量化:地下温度,地下水速度和地表热通量。对于所有包含地下温度曲线的目标,PEST衍生的模型敏感性均相似,而与全年数据相比,当仅以夏季条件为目标时,敏感性略高。这种趋势归因于夏季月份在地面的热交换更多,从而导致了更活跃的地下水流系统和对热态的更多反馈。对于所有目标,浅层(分别为细砂和海洋淤泥)的水力和热力参数以及定义地表热交换层的参数与较深层(粗砂和砾石,和未破裂的基岩)。地表热通量目标的灵敏度也最高。

更新日期:2020-04-21
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