Controls of soil organic matter on soil thermal dynamics in the northern high latitudes

Dan Zhu,Gustaf Hugelius,Fabienne Maignan,Gerhard Krinner,Albert Jornet Puig,Philippe Ciais

doi:10.1038/s41467-019-11103-1

Abstract

Permafrost warming and potential soil carbon (SOC) release after thawing may amplify climate change, yet model estimates of present-day and future permafrost extent vary widely, partly due to uncertainties in simulated soil temperature. Here, we derive thermal diffusivity, a key parameter in the soil thermal regime, from depth-specific measurements of monthly soil temperature at about 200 sites in the high latitude regions. We find that, among the tested soil properties including SOC, soil texture, bulk density, and soil moisture, SOC is the dominant factor controlling the variability of diffusivity among sites. Analysis of the CMIP5 model outputs reveals that the parameterization of thermal diffusivity drives the differences in simulated present-day permafrost extent among these models. The strong SOC-thermics coupling is crucial for projecting future permafrost dynamics, since the response of soil temperature and permafrost area to a rising air temperature would be impacted by potential changes in SOC.

Highlights

Permafrost warming and potential soil carbon (SOC) release after thawing may amplify climate change, yet model estimates of present-day and future permafrost extent vary widely, partly due to uncertainties in simulated soil temperature
We find a significant negative correlation between soil thermal diffusivity and soil organic carbon density (Fig. 1)
This suggests that the impact of soil organic carbon (SOC) on D is a composite result of soil composition and structure alterations such that its correlation with D cannot be fully accounted for by the variability in the texture- and porosity-related properties

Summary

Introduction

Permafrost warming and potential soil carbon (SOC) release after thawing may amplify climate change, yet model estimates of present-day and future permafrost extent vary widely, partly due to uncertainties in simulated soil temperature. 1234567890():,; Soils in the northern permafrost region contain ~1300 ± 300 Pg of soil organic carbon (SOC)[1,2,3], more than one-third of the global total SOC4, formed under cold climates with limited decomposition Carbon release from this large pool due to warming-induced thawing and acceleration of microbial decomposition may act as an important positive feedback to climate change, but the magnitude and timing of this carbon release remains uncertain[3,5,6,7]. SOC storage in permafrost soils and the high vulnerability and sensitivity of these carbon stocks to projected warming[6,18], it is important to assess the quantitative impact of SOC on D and the potential acceleration of soil warming due to the loss of SOC and its insulating effect

Methods

Results

Conclusion