Abstract
Abstract. Freeze/thaw (F/T) processes can be quite different under the various land surface types found in the complex tundra of the Arctic, such as polygonal tundra (wet center and dry rims), ponds, and thermokarst lakes. Proper simulation of these different processes is essential for accurate prediction of the release of greenhouse gases under a warming climate scenario. In this study we have incorporated the water layer into a dynamic organic soil version of the Terrestrial Ecosystem Model (DOS-TEM), having first verified and validated the model. Results showed that (1) the DOS-TEM was very efficient and its results compared well with analytical solutions for idealized cases, and (2) despite a number of limitations and uncertainties in the modeling, the simulations compared reasonably well with in situ measurements from polygon rims, polygon centers (with and without water), and lakes on Samoylov Island, Siberia, indicating the suitability of the DOS-TEM for simulating the various F/T processes. Sensitivity tests were performed on the effects of water depth and our results indicated that both water and snow cover are very important in the simulated thermal processes, for both polygon centers and lakes. We therefore concluded that the polygon rims and polygon centers (with various maximum water depths) should be considered separately, and that the dynamics of water depth in both polygons and lakes should be taken into account when simulating thermal processes for methane emission studies.
Highlights
The release of greenhouse gases from the large quantities of soil carbon preserved in Arctic regions constitutes an important feedback to climatic warming and the thawing of permafrost north of 45◦ N (McGuire et al, 2009; Schneider von Deimling et al, 2012)
Heterogeneous ground surfaces with, for example, variable snowpack or organic layer thicknesses exert a major influence on the surface energy balance (Etzelmüller and Frauenfeld, 2009) and have in the past been integrated into both land surface models (Yi et al, 2007; Lawrence and Slater, 2008) and ecosystem models (Zhuang et al, 2001; Yi et al, 2009a, b, 2010)
Few of the current large-scale land surface models or ecosystem models take into account the effects that water bodies have on the dynamics of permafrost (Zhuang et al, 2006; Ringeval et al, 2012), with one exception being the model by Wania et al (2009) which treated surface water in the same way as a litter layer
Summary
The release of greenhouse gases from the large quantities of soil carbon preserved in Arctic regions constitutes an important feedback to climatic warming and the thawing of permafrost north of 45◦ N (McGuire et al, 2009; Schneider von Deimling et al, 2012). Water bodies of various sizes, ranging from those occupying polygon centers to large thermokarst lakes, are distributed across the Arctic coastal regions (French, 2007) resulting in considerable landscape heterogeneity. These water bodies have a marked effect on the surface energy balance and thermal dynamics of the surrounding permafrost soils (French, 2007). Their presence can lead to permafrost degradation, which in turn affects the terrestrial ecosystem’s carbon budget.
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