Numerical simulation of the impacts of climate warming on a permafrost mound

Abstract

A finite-element, one-dimensional, heat conduction model, which takes thaw settlement into account following drainage of excess water produced by the melt of ice lenses at the permafrost boundaries, is used to assess the thermal response of a permafrost mound in Northern Québec to different scenarios of climate warming. In addition to the cryostratigraphy of the mound, the unfrozen water content, thermal conductivity and volumetric heat capacity of the marine sediments comprising the mound were integrated in the simulation.Warming rates from 0.03 to 0.01 C/year are predicted in the mound for a gradual linear increase in mean annual air temperature of 0.05 C/year over a 100 year period. Downward thawing occurs at the permafrost table at rates of 1-13 cm/year but there is also upward thawing from the permafrost base at rates of 2.4-5.8 cm/year. The thermal response of permafrost is not linear with time. At the end of the 100 year period, thaw settlement predicted was 1.4 m and the active layer was 3.22 m thick over a talik of 1.46 m thick. This is in comparison to an active layer of 2.14 m thick over a talik of 1.86 m if thaw settlement is not considered in the simulation. Thaw settlement, the direct result of ice melting in permafrost, brings permafrost nearer to the surface and accelerates its thawing. It should be included in any numerical simulation.

Characteristics and fate of isolated permafrost patches in coastal Labrador, Canada

“…To achieve these matches, the geothermal heat fluxes were set to 0.54 and 1.02 W m -2 , respectively. These fluxes are an order of magnitude larger than the geothermal heat flux in deep ground (Pollack et al, 1993) but are similar to values used for modelling permafrost mounds in northern Québec (Buteau et al, 2004). They likely reflect advective and vertical heat flow from surrounding unfrozen terrain and water in deep ground rather than being the geothermal heat flow at depth.…”

Advancement toward coupling of the VAMPER permafrost model within the Earth system model <I>i</I>LOVECLIM (version 1.0): description and validation

“…Some parameterizations include organic and mineral layer thicknesses, which give soil properties such as porosity and bulk density, and unfrozen water content characteristics. Examples of these sitespecific studies include, for example, Romanovsky and Osterkamp (1995), Buteau et al (2004), Ling, Zhang (2004), and Zhang et al (2008), and Nicolsky et al (2009). Since VAMPER is not parameterized to capture site-specific behavior, it is challenging to assess the ability of the model to simulate active layer dynamics.…”

“…However, it should be noted that there is a difference between coupled models which actively integrate the role of permafrost (including the thermal, hydrological, and/or carbon feedbacks) (Lawrence et al, 2011), and models which look at permafrost in a post-processing perspective (e.g., Buteau et al, 2004;Ling and Zhang, 2004) meaning they are forced by the predicted temperature changes. It is the full coupling with integrated feedbacks which is a current interest of ours, where the goal is to fully couple ECBilt and VAMPERS within iLOVECLIM.…”

Impact of permafrost thaw on the turbidity regime of a subarctic river: the Sheldrake River, Nunavik, Quebec

“…The thermal model is driven by cumulative thawing degree-days gathered from the meteorological station. Clay and silt thermal parameters of the model's PRAM routine with a water content of 20% and only one stratigraphic layer were applied in the simulations as in other studies in the region (Buteau et al 2004). Grain size composition is rather homogenous throughout the clay soils of the region (Calmels 2005).…”