Numerical Modeling of the Active Layer Thickness and Permafrost Thermal State Across Qinghai‐Tibetan Plateau

Abstract

The dynamics of permafrost (including the permafrost thermal state and active layer thicknesses (ALT)) across the Qinghai‐Tibetan Plateau (QTP) have not been well understood on a large scale. Here we simulate the ALT and permafrost thermal state using the Geophysical Institute Permafrost Lab version 2 (GIPL2) model across the QTP. Based on the single‐point simulations, the model is upscaled to the entire QTP. The upscaled model is validated with five investigated regions (IRs), including Wenquan (WQIR), Gaize (GZIR), Aerjin (AEJIR), Xikunlun (XKLIR), and Qinghai‐Tibetan Highway (G109IR). The results show that the modified GIPL2 model improves the accuracy of the permafrost thermal state simulations. Due to our simulated results on the QTP, the average ALT is of 2.30 m (2.21–2.40 m). The ALT decreases with an increase in the altitude and decreases from the southeast to the northwest. The ALT is thin in the central QTP, but it is thick in the high‐elevation mountain areas and some areas surrounding glaciers and lakes. The largest ALT is found in the border areas between permafrost and seasonally frozen ground regions. The simulated results of the MAGT (the mean annual ground temperature) indicate that most of the permafrost is substable, which is sensitive to climate warming. The simulated results would be of great significance on assessing the impacts of permafrost dynamics on local hydrology, ecology, and engineering construction.

Soil moisture temporal stability and spatio‐temporal variability about a typical subalpine ecosystem in northwestern China

“…Spatial–temporal variability and soil water relations that occur within and among different vegetation types play an important role in eco‐hydrological processes and sustainable development of ecosystems in arid and semi‐arid areas (del Campo et al, ). In addition to the confluence of slope, the characteristics of plant canopies, distribution of plants roots, and soil freezing and thawing processes affected soil water relations between adjacent vegetation types (Ellis et al, ; Grant et al, ; Qin et al, ; Starkloff, Stolte, Hessel, Ritsema, & Jetten, ; Williams, McNamara, & Chandler, ; Zhang et al, ). We found that temporal patterns of VSWC in 0–20 cm soil layer and 0–70 cm soil profile were significantly correlated ( p < .01) among all three vegetation types (Table ).…”

Elevation‐dependent thermal regime and dynamics of frozen ground in the Bayan Har Mountains, northeastern Qinghai‐Tibet Plateau, southwest China

“…The depth at which temperature changes by no more than 0.1°C throughout a year is defined as the depth of zero annual amplitude (ZAA) . It depends on factors including soil thermo‐physical properties, surface characteristics and topography.…”

“…We used the Geophysical Institute Permafrost Lab (GIPL) model to simulate the dynamics of frozen ground during 1980–2017 at QSH‐1. This model was developed by the Geophysical Institute Permafrost Lab, University of Alaska Fairbanks, and has been widely used to simulate site‐specific or regional thermal conditions of permafrost . It numerically simulates soil temperature dynamics and the depths of seasonal freezing and thawing by solving a one‐dimensional non‐linear heat equation with phase change: H ( x , t ) is the enthalpy function, which is given by: where x ∈ ( x u , x l ) is a spatial variable that changes with depth, x u and x l are the upper and lower boundary of the temperature profile, corresponding to 0 and 100 m; τ ∈ (0, T ) is the temporal variable and t ( x , τ ) is temperature.…”

“…To determine the effects of elevation, topography and surface charac- throughout a year is defined as the depth of zero annual amplitude (ZAA). 40,41 It depends on factors including soil thermo-physical properties, surface characteristics and topography. ZAA, which is theoretically considered to be thermally stable within a year, was thus used to distinguish the thermal regime of permafrost in the BHM.…”

“…This model was developed by the Geophysical Institute Permafrost Lab, University of Alaska Fairbanks, and has been widely used to simulate site-specific or regional thermal conditions of permafrost. 41,43 It numerically simulates soil temperature dynamics and the depths of seasonal freezing and thawing by solving a one-dimensional non-linear heat equation with phase change 44 :…”