Sensitivity of soil freeze/thaw dynamics to environmental conditions at different spatial scales in the central Tibetan Plateau

Huiru Jiang; Yonghong Yi; Wenjiang Zhang; Kun Yang; Deliang Chen

doi:10.1016/j.scitotenv.2020.139261

Sensitivity of soil freeze/thaw dynamics to environmental conditions at different spatial scales in the central Tibetan Plateau

Sci Total Environ. 2020 Sep 10:734:139261. doi: 10.1016/j.scitotenv.2020.139261. Epub 2020 May 15.

Authors

Huiru Jiang¹, Yonghong Yi², Wenjiang Zhang³, Kun Yang⁴, Deliang Chen⁵

Affiliations

¹ Regional Climate Group, Department of Earth Sciences, University of Gothenburg, Gothenburg, Sweden; State Key Laboratory of Hydraulics and Mountain River, Sichuan University, Chengdu 610065, China.
² Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.
³ State Key Laboratory of Hydraulics and Mountain River, Sichuan University, Chengdu 610065, China.
⁴ Department of Earth System Science, Tsinghua University, Beijing 100084, China.
⁵ Regional Climate Group, Department of Earth Sciences, University of Gothenburg, Gothenburg, Sweden. Electronic address: deliang@gvc.gu.se.

PMID: 32454333
DOI: 10.1016/j.scitotenv.2020.139261

Abstract

An enhanced understanding of environmental controls on soil freeze/thaw (F/T) dynamics at different spatial scales is critical for projecting permafrost responses to future climate conditions. In this study, a 1-D soil thermal model and multi-scale observation networks were used to investigate the sensitivity of soil F/T dynamics in the central Tibetan Plateau (TP) to environmental conditions at local (~10 km)-, medium- (~30 km), and large (~100 km)- scales. Model simulated soil temperature profile generally agrees well with the observations, with root-mean-square errors (RMSE) lower than 1.3 °C and 2.0 °C for two in-situ networks, respectively. Model simulated maximum frozen depths (MFD) closely related to elevation (R² = 0.23, p < 0.01), soil moisture content (R² = 0.25, p < 0.01), and soil organic carbon (SOC) content (R² = 0.18, p < 0.01); however, the impact of SOC on MFD may be due to the close correlation between SOC and soil moisture. The main factors affecting MFD vary with scale. Among the environmental factors examined, topography (especially elevation) is the first-order factor controlling the MFD at the large-scale, indicating the dominance of thermal control. Aspect shows sizeable impacts at the medium-scale, while soil moisture plays an important role at the local-scale. Soil thaw onset shows a close correlation with the examined environmental factors including soil moisture, while freeze onset seems to be influenced more by other factors. Besides the well-known thermal effect, our study highlights the importance of soil moisture in affecting soil F/T dynamics at different scales in the central TP region, and reliable soil moisture products are critical to better project the response of the TP frozen ground to future warming at finer scale.

Keywords: Central Tibetan Plateau; Maximum frozen depth; Soil freeze/thaw dynamics; Soil moisture; Topography.