Modeling biogeophysical interactions in nonsorted circles in the Low Arctic

Abstract

[1] We investigate biogeophysical processes that cause differential frost heave in nonsorted circles north of the Alaska's Brooks Range. The main objective is the development of a numerical thermo-mechanical model of a nonsorted circle. The presented model includes mass, momentum and energy conservation laws for water, ice and soil. We applied this model to simulate differential frost heave at the Franklin Bluffs site and obtained a good quantitative agreement with measured dynamics of soil temperature, water content, and frost heave. For other locations such as at the Sagwon Hills and Howe Island sites we obtained qualitative agreement with frost-heave measurements. Sensitivity analysis shows that the most active development of differential frost heave occurs for nonsorted circles within waterlogged areas, as observed in field measurements. For well drained sites, model results and field observations show that the differential frost heave is much smaller in magnitude comparing to that of the water-logged sites. Sensitivity of the model to alternation of the vegetation cover shows that a strong heterogeneity in the vegetation cover promotes active development of the differential frost heave. For nonsorted circles with vegetation on top of the circle, the computed differential heave is less pronounced. The radius of the nonsorted circle influences the magnitude of the frost heave. The computed maximum frost heave in the center of the circle corresponds to 1-1.5 meter diameter nonsorted circles. For nonsorted circles with larger diameters, computed frost heave in the center of a circle is smaller compared to the heave at the circle circumference.

Stone circles: form and soil kinematics

“…The latter include the strong influence of the developing topography and textural differentiation on the transport of heat and moisture that fuel the development of sorted patterned ground. These studies of the stability of secondary frost heaving have much in common with recent models that focus on the formation of non-sorted patterned ground [44][45][46][47].…”

Interaction of geomorphic and ecologic features across altitudinal zones in a subarctic landscape

“…A strong two-way linkage exists, however, between, for example, vegetation and cryoturbation activity: vegetation influences the heat regimes and the moisture conditions of the soil, and cryoturbation affects the plant colonization . Still, the determination of the direction of the interaction can be a difficult task even at a fine scale because the same thermal, soil textural, and hydrological properties are the important controls for cryoturbation and vegetation (Zeng et al, 2007;Nicolsky et al, 2008;Raynolds et al, 2008).…”

Permafrost Sub-grid Heterogeneity of Soil Properties Key for 3-D Soil Processes and Future Climate Projections

“…This vertical soil organic matter distribution is distinct from the monotonically decreasing carbon profile in temperate soils (Jobbágy and Jackson, 2000). The underlying forces for several processes leading to such large heterogeneity are freeze-thaw cycles and associated movement of water and soil particles in all three spatial dimensions (Yershov, 1998;Nicolsky et al, 2008;Woo, 2012). That means that 3-D processes at the cm-scale, such as water flux toward the freezing front, ice lens formation and frost sorting largely determine soil state heterogeneity in turbels (French, 2013).…”

“…Such soil transport called cryoturbation is widely observed Hugelius et al, 2010;Gentsch et al, 2015), however, it has to my knowledge never been simulated mechanistically, also not at the smallest spatial scale. Even if that was possible with a mechanistic model, e.g., following principles presented by Nicolsky et al (2008), yet, we do not have any appropriate mathematical solution in hand for such 3-D process at a landscape scale, that is as a sub-grid processes inside a 0.5 • grid cell. Transport processes can be represented by a few first terms of the master equation representing diffusion and advection processes (Koven et al, 2009;Braakhekke et al, 2011Braakhekke et al, , 2014Ahrens et al, 2015).…”

“…Such approach can be used to simulate monotonically decreasing carbon content with depth (temperate soil) but this method completely fails when distinct large peaks of carbon concentration occur in a certain depth due to cryoturbation. Controlled fine-scale experiments using fully mechanistic models, such as Nicolsky et al (2008) are required in order to find any parametrization at broader scales for LSMs. This is because any observations of soil state variables, e.g., carbon or ice content will be confounded by many different factors not related to transport processes itself (evapotranspiration effect on soil moisture, decomposition effects on carbon content etc.).…”