Abstract
There are massive carbon stocks stored in permafrost-affected soils due to the 3-D soil movement process called cryoturbation. For a reliable projection of the past, recent and future Arctic carbon balance, and hence climate, a reliable concept for representing cryoturbation in a land surface model (LSM) is required. The basis of the underlying transport processes is pedon-scale heterogeneity of soil hydrological and thermal properties as well as insulating layers, such as snow and vegetation. Today we still lack a concept of how to reliably represent pedon-scale properties and processes in a LSM. One possibility could be a statistical approach. This perspective paper demonstrates the importance of sub-grid heterogeneity in permafrost soils as a pre-requisite to implement any lateral transport parametrization. Representing such heterogeneity at the sub-pixel size of a LSM is the next logical step of model advancements. As a result of a theoretical experiment, heterogeneity of thermal and hydrological soil properties alone lead to a remarkable initial sub-grid range of subsoil temperature of 2 deg C, and active-layer thickness of 150 cm in East Siberia. These results show the way forward in representing combined lateral and vertical transport of water and soil in LSMs.
Highlights
Reviewed by: Vincent Vionnet, Centre d’Etudes de la Neige, France Evgeny Andreevich Podolskiy, Hokkaido University, Japan Lukas Arenson, BGC Engineering, Canada
As a result of a theoretical experiment, heterogeneity of thermal and hydrological soil properties alone lead to a remarkable initial sub-grid range of subsoil temperature of 2◦C, and active-layer thickness of 150 cm in East Siberia
Soil processes such as soil organic matter dynamics are widely recognized as only temporal processes without any spatial dimension (Schmidt et al, 2011; Lehmann and Kleber, 2015)
Summary
Earth is a complex system and its compartments (atmosphere, ocean, land) are interacting with each other. Any attempt of mechanistically model the contribution of soil warming and permafrost thawing to ecosystem respiration change will fail, basically because the carbon profile is not represented This is a problem of major importance for future climate projection because high latitude permafrost regions store massive amounts of soil organic matter compared to the atmosphere (Table 1), and climate has been changing. Most in these regions providing the basis for a strong carbon cycle-climate feedback mechanism (McGuire et al, 2006, 2009; Beer, 2008; Heimann and Reichstein, 2008; Schuur et al, 2013, 2015) Another consequence of patterned ground formation is a resulting high heterogeneity of aerobic vs anaerobic conditions in permafrost regions (Schuur et al, 2008) leading to distinct decomposition pathways to carbon dioxide and methane. Thawing permafrost may result in a larger soil subsidence called thermokarst (Grosse et al, 2011) which can lead to lake development (Fedorov et al, 2014; Johansson et al, 2015) thereby altering completely landscape conditions
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