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: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=680028
• 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与永久冻土退化相关的地质灾害中，融化沉降的脆弱性是普遍存在的。多年冻土的融化固结与含水量、低温结构、土壤质地、融化速率和孔隙水压力消散密切相关。然而，人们对退化的永久冻土层中融化的地面冰所产生的水的去向知之甚少。孔隙水耗散如何控制融化固结？融水从哪里流入地下？融水是在深层补给含水层，还是在地表迁移并最终进入湖泊、河流和海洋？ ***作为研究假设和正反馈，取决于孔隙水压力消散的融化沉降加速了多年冻土退化的速度。地表的温暖边界正在向下移动到深处正在退化的永久冻土体，这增加了永久冻土的融化。 ***为了检验这一研究假设，目标是：***1）在现场观察、描述和监测永久冻土退化的过程，***2）测量富含冰的永久冻土的融化固结特性实验室测试，***3) 模拟永久冻土退化中发生的传热、融化固结和融水流动，***4) 将这些模拟过程与观测结果进行比较，***5) 预测永久冻土退化将来。 ***研究地点位于加拿大魁北克省北部 Umiujaq 附近的不连续永久冻土带，那里富含冰的永久冻土丘已经开始退化。多个地点的地温和解冻沉降数据的长期监测系列已经可用。 ***本研究计划中使用的方法在很大程度上依赖于使用不同监测技术（自动热敏电阻电缆、水位记录仪、LiDAR 调查以及可见光和红外摄影测量）、岩土工程和地球物理工具（永久冻土采样、电学）进行仔细现场观察的地面实况。电阻率和地震折射断层扫描），以及对富含冰的永久冻土样品的实验室测试（融化固结和导水率）。将进行热-水-机械过程的数值模拟，以模拟不同气候变化情景下的永久冻土退化。 ***该研究计划的预期成果是更好地了解永久冻土退化中发生的物理过程，并改进相变、融化固结、融水迁移和流动的传热数值模型，以预测由于永久冻土退化而导致的永久冻土退化。气候变化。根据该研究计划中开发的知识，可以制定适应战略以确保加拿大北部的可持续发展。