August 15, 2016

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Influences and Interactions of Inundation, Peat, and Snow and Active Layer Thickness

Active layer response across gradients of environmental conditions.

The Science

Researchers used a physics-based numerical model validated at the Barrow (Alaska) Environmental Observatory to simulate the subsurface thermal hydrological response in permafrost tundra due to changing environmental conditions in organic soil layer thickness, snow depth, soil saturation, and ponded depth.

The Impact

Researchers mapped the complex interaction of isolated environmental conditions that govern permafrost conditions. As a result, Arctic tundra response to changing conditions either by naturally occurring environmental gradients or by climate-induced perturbations can be inferred.


The collective work provides details on active layer thickness (ALT), or annual thaw depth above permafrost, related to three important environmental conditions characteristic of Arctic permafrost tundra: (1) organic soil layer thickness, (2) snow depth, and (3) unsaturated to inundated conditions. The work teases out how ALT will change as gradients along these environmental conditions are traversed in either space or time. One finding indicates that wetting or drying of polygonal tundra appears to have a minor effect on ALT compared to organic layer thickness and snow. At the same time, however, the inundation state is very interactive and can act to amplify other conditions that influence ALT; so much so, that subsurface thermal tipping points can be crossed. For example, the combined effect of inundation depth and snow can cause taliks, zone of year-round unfrozen soil, to form.

Principal Investigator

Adam Atchley
Los Alamos National Laboratory
[email protected]

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
[email protected]


This work was supported by the Los Alamos National Laboratory’s Laboratory-Directed Research and Development project (LDRD201200068DR) and by the Next-Generation Ecosystem Experiments (NGEE)–Arctic project. NGEE-Arctic is supported by the Office of Biological and Environmental Research within the U.S. Department of Energy Office of Science.


Atchley, A. L., E. T. Coon, S. L. Painter, and D. R. Harp, et al.. "Influences and interactions of inundation, peat, and snow and active layer thickness." Geophysical Research Letters 43 (10), 5116–5123  (2016).

Atchley, A. L., S. L. Painter, D. R. Harp, and E. T. Coon, et al. "Using field observations to inform thermal hydrology models of permafrost dynamics with ATS (v0.83)." Geoscientific Model Development 8 (9), 2701–2722  (2015).