CVPM

Multidimensional heat-transfer modeling system for permafrost with advanced unfrozen water physics. The Control Volume Permafrost Model (CVPM) is a modular heat-transfer modeling system designed for scientific and engineering studies in permafrost terrain, and as an educational tool. CVPM implements the nonlinear heat-transfer equations in 1-D, 2-D, and 3-D cartesian coordinates, as well as in 1-D radial and 2-D cylindrical coordinates. To accommodate a diversity of geologic settings, a variety of materials can be specified within the model domain, including: organic-rich materials, sedimentary rocks and soils, igneous and metamorphic rocks, ice bodies, borehole fluids, and other engineering materials. Porous materials are treated as a matrix of mineral and organic particles with pore spaces filled with liquid water, ice, and air. Liquid water concentrations at temperatures below 0°C due to interfacial, grain-boundary, and curvature effects are found using relationships from condensed matter physics; pressure and pore-water solute effects are included. A radiogenic heat-production term allows simulations to extend into deep permafrost and underlying bedrock. CVPM can be used over a broad range of depth, temperature, porosity, water saturation, and solute conditions on either the Earth or Mars. The model is suitable for applications at spatial scales ranging from centimeters to hundreds of kilometers and at timescales ranging from seconds to thousands of years. CVPM can act as a stand-alone model, the physics package of a geophysical inverse scheme, or serve as a component within a larger earth modeling system that may include vegetation, surface water, snowpack, atmospheric or other modules of varying complexity.

permafrostheat-transfermultidimensionalEarthMars

Alias

Control Volume Permafrost Model

true

Contributor(s)

Initial contribute: 2021-09-14

Authorship

:  
Institute of Arctic and Alpine Research
:  
gclow@colorado.edu
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Classification(s)

Application-focused categoriesNatural-perspectiveLand regions
Application-focused categoriesNatural-perspectiveFrozen regions

Detailed Description

English {{currentDetailLanguage}} English

To investigate the permafrost thermal state of seasonally flooded river and delta floodplains, we need to propagate the simulated water temperature T was the upper boundary condition into a model that predicts permafrost temperature with depth (CVPM). CVPM is a nonlinear heat‐transfer model for permafrost terrain recently developed by Clow (2018a). The model assumes advective heat flu x is negligible compared to the diffusive heat flux, so that the enthalpy flux becomes a function of bulk thermal conductivity and temperature gradient. Unfrozen water contents below 0 °C are found taking in account interfacial, grain boundary, curvature, pore‐water solute, and pressure effects. The model domain is highly flexible and can be set for a variety of dimensions, temporal and spatial scales. CVPM's numerical implementation is based on the control‐volume method; namely, the model domain can be divided into discrete control volumes over which a given substrate is relatively uniform. Soil temperature Ts is computed at points located in the center of the control volumes, while the heat fluxes are computed at control‐volume interfaces. CVPM is designed to account for a large variety of materials including deposits typical of river floodplains, such as organic rich

materials, fine‐grained sedimentary materials, sand, and gravel. Input variables required for CVPM include the initial conditions, boundary conditions (temperature or heat flux), and a number of parameters specifying the thermophysical properties of the soils or sedimentary materials (Table 1, No. 32–45). Output variables include soil temperature Ts, thermal diffusivity, volume fraction of ice, and liquid water content. For a detailed description of the physical basis of the CVPM model, we refer to Clow (2018a). The model code and user's manual (Clow, 2018b) are available at GitHub.

All simulations for this study are one dimensional (vertical), even for the applications across the channelbelt and floodplain, as CVPM does not currently allow an undulating topographically variable upper boundary in two‐dimensional implementations. Measured ground surface temperature Tg, or water temperature Tw when either the channel contains water or thefloodplain is inundated, serves as the upper boundary condition for the permafrost model. Then, subsurface thermal simulations are conducted to a depth of 70 m while the lower boundary heat flux is set to zero. The depth resolution of the model grid is 0.01 m for the upper 9 m and 6 m below that. It is an intractable problem to estimate a realistic initial condition in the absence of continuous deep soil temperature measurements. One common strategy, which we employ as well, as an alternative for direct observations is to establish an equilibration profile with long‐term ground temperature records (Riseborough et al., 2008). In this study, an initial subsurface temperature profile is established by a 100year spin‐up procedure with repeated annual ground surface temperature Tg cycles.

Quoted from : Changing Arctic River Dynamics Cause Localized Permafrost Thaw

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Contributor(s)

Initial contribute : 2021-09-14

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Authorship

:  
Institute of Arctic and Alpine Research
:  
gclow@colorado.edu
Is authorship not correct? Feed back

History

Last modifier
Yihan Zhang
Last modify time
2021-09-18
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