Site-level model intercomparison of high latitude and high altitude soil thermal dynamics in tundra and barren landscapes

A Ekici,E Burke,A Marmy,L H Hajdu,M Langer,S Chadburn,A D Friend,C Hauck,N Chaudhary,P A Miller,C Beer,S Peng,J Boike,G Krinner

doi:10.5194/tc-9-1343-2015

Abstract

Abstract. Modeling soil thermal dynamics at high latitudes and altitudes requires representations of physical processes such as snow insulation, soil freezing and thawing and subsurface conditions like soil water/ice content and soil texture. We have compared six different land models: JSBACH, ORCHIDEE, JULES, COUP, HYBRID8 and LPJ-GUESS, at four different sites with distinct cold region landscape types, to identify the importance of physical processes in capturing observed temperature dynamics in soils. The sites include alpine, high Arctic, wet polygonal tundra and non-permafrost Arctic, thus showing how a range of models can represent distinct soil temperature regimes. For all sites, snow insulation is of major importance for estimating topsoil conditions. However, soil physics is essential for the subsoil temperature dynamics and thus the active layer thicknesses. This analysis shows that land models need more realistic surface processes, such as detailed snow dynamics and moss cover with changing thickness and wetness, along with better representations of subsoil thermal dynamics.

Highlights

Recent atmospheric warming trends are affecting terrestrial systems by increasing soil temperatures and causing changes in the hydrological cycle
In high latitudes and altitudes, clear signs of change have been observed (Serreze et al, 2000; ACIA, 2005; IPCC AR5, 2013). These relatively colder regions are characterized by the frozen state of terrestrial water, which brings additional risks associated with shifting soils into an unfrozen state
There are increasing concerns as to how land models perform at capturing high latitude soil thermal dynamics, in particular in permafrost regions

Summary

Introduction

Recent atmospheric warming trends are affecting terrestrial systems by increasing soil temperatures and causing changes in the hydrological cycle. In high latitudes and altitudes, clear signs of change have been observed (Serreze et al, 2000; ACIA, 2005; IPCC AR5, 2013). These relatively colder regions are characterized by the frozen state of terrestrial water, which brings additional risks associated with shifting soils into an unfrozen state. Such changes will have broad implications for the physical (Romanovsky et al, 2010), biogeochemical (Schuur et al, 2008) and structural (Larsen et al, 2008) conditions of the local, regional and global climate system. Recent studies (Koven et al, 2013; Slater and Lawrence, 2013) have provided detailed assessments of commonly used earth system models (ESMs) in simulating soil temperatures of present and future state

Objectives

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Conclusion