Three-phase numerical model for subsurface hydrology in permafrost-affected regions (PFLOTRAN-ICE v1.0)

• Published in: The Cryosphere
• Main Authors: S. Karra, S. L. Painter, P. C. Lichtner
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2014
• Subjects: Environmental sciences; GE1-350; Geology; QE1-996.5; Arctic; Ice; permafrost; The Cryosphere; Tundra
• Online Access: https://doi.org/10.5194/tc-8-1935-2014; https://doaj.org/article/e5bbcc10faa34b089fb42d3722ca5ab1

Degradation of near-surface permafrost due to changes in the climate is expected to impact the hydrological, ecological and biogeochemical responses of the Arctic tundra. From a hydrological perspective, it is important to understand the movement of the various phases of water (gas, liquid and ice) during the freezing and thawing of near-surface soils. We present a new non-isothermal, single-component (water), three-phase formulation that treats air as an inactive component. This single component model works well and produces similar results to a more complete and computationally demanding two-component (air, water) formulation, and is able to reproduce results of previously published laboratory experiments. A proof-of-concept implementation in the massively parallel subsurface flow and reactive transport code PFLOTRAN is summarized, and parallel performance of that implementation is demonstrated. When water vapor diffusion is considered, a large effect on soil moisture dynamics is seen, which is due to dependence of thermal conductivity on ice content. A large three-dimensional simulation (with around 6 million degrees of freedom) of seasonal freezing and thawing is also presented.