The fate of water from melting ground ice in degrading permafrost environment

在退化的永久冻土环境中融化的地面冰所产生的水的命运

• 批准号: RGPIN-2017-06544
• 负责人: Fortier, Richard
• 金额: $ 1.75万
• 依托单位: Université Laval
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=712260
• 关键词: fate; water; melting; ground; ice

Among the geohazards associated with permafrost degradation which impact the sustainable development of Northern Canada, the vulnerability to thaw subsidence is widespread. The thaw consolidation of permafrost is closely related to water content, cryostructure, soil texture, rates of thawing and dissipation of pore water pressure. However, little is known on the fate of water from melting ground ice in degrading permafrost. How does the pore water dissipation control the thaw consolidation? Where the meltwater is flowing into the ground? Is the meltwater recharging the aquifers at depths or is it migrating at the ground surface and ultimately finding its way in lakes, rivers, and oceans? As a research hypothesis and a positive feedback, the thaw subsidence which depends on the dissipation of pore water pressure accelerates the rate of permafrost degradation. The warm boundary at the ground surface is moving downwards toward the degrading permafrost body at depths which increases the permafrost thawing. For testing this research hypothesis, the objectives are to: 1) observe, describe, and monitor in the field the processes of permafrost degradation, 2) measure the thaw consolidation properties of ice-rich permafrost from laboratory tests, 3) simulate the heat transfer, thaw consolidation and flow of meltwater which are taking place in degrading permafrost, 4) compare these simulated processes with the observations, and 5) anticipate the permafrost degradation in the future. The study site is located in the discontinuous permafrost zone close to Umiujaq in northern Quebec, Canada, where ice-rich permafrost mounds are already degrading. Long-term monitoring series of ground temperature and thaw subsidence data are already available for several locations. The methodology used in this research program relies heavily on ground truth from careful field observations using different monitoring techniques (automated thermistor cables, water level loggers, LiDAR surveys and visible and infrared photogrammetry), geotechnical and geophysical tools (permafrost sampling, electrical resistivity and seismic refraction tomography), and lab tests on ice-rich permafrost samples (thaw consolidation and hydraulic conductivity). Numerical modelling of thermal-hydro-mechanical processes will be performed to simulate permafrost degradation following different scenarios of climate changes. The expected outcomes from this research program are a better understanding of the physical processes which are taking place in degrading permafrost and the improvement of numerical modelling of heat transfer with phase change, thaw consolidation, meltwater migration and flow to anticipate permafrost degradation due to climate changes. From the knowledge developed in this research program, adaptation strategies could be established to insure the sustainable development of Northern Canada.

在影响加拿大北部可持续发展的多年冻土降解相关的地质灾害中，融化沉降的脆弱性很普遍。多年冻土的融化巩固与水含量，冷冻结构，土壤质地，解冻速率和孔隙水压耗散密切相关。然而，在融化地面冰层中熔融冰冻冰冻的命运中，知之甚少。孔隙水耗散如何控制融化巩固？融化流入地面的何处？融水是在深处充电含水层还是在地面迁移并最终在湖泊，河流和海洋中找到道路？ 作为研究假设和正反馈，取决于孔隙水压耗散的融化沉降加速了多年冻土降解的速度。地面上的温暖边界在深处向下移动朝着降解的永久冻土体移动，从而增加了永久冻土融化。 为了检验该研究假设，目标是： 1）在现场观察，描述和监视多年冻土降解的过程， 2）测量实验室测试中富含冰块的冰块融化特性， 3）模拟在降解的多年冻土中发生的热传递，融化和流动的融化和流动 4）将这些模拟过程与观测值进行比较，并将其比较 5）预计将来会有多年冻土降解。 该研究地点位于加拿大魁北克北部的Umiujaq附近的不连续的多年冻土带，那里的富含冰块的多年冻土土墩已经在降级。长期监测的地面温度和融化沉降数据已经可用于多个位置。 该研究计划中使用的方法在很大程度上取决于使用不同监测技术（自动化热电缆，水位记录仪，LIDAR调查以及可见的和红外摄影测量法），岩土技术和地球物理工具（成年的电阻和电阻，电阻，电气电阻，电气电阻，电气电阻，电阻，电阻，电源摄影仪和红外摄影，折射断层扫描）以及对富含冰块的多年冻土样品（融化合并和液压传导率）的实验室测试。将在气候变化的不同情况下，将对热融化机械过程的数值建模进行模拟永久冻土降解。 该研究计划的预期结果更好地理解了在降解多年冻土和随着相变，融化的巩固，融化，融合水的迁移和流量的预测，由于气候变化而导致的多年冻土迁移和流动的改善，并改善了热传递的数值建模。从本研究计划中开发的知识中，可以建立适应策略，以确保加拿大北部的可持续发展。