Simulating the current and future northern limit of permafrost on the Qinghai–Tibet Plateau

Author:

Zhao Jianting,Zhao LinORCID,Sun Zhe,Niu Fujun,Hu Guojie,Zou Defu,Liu GuangyueORCID,Du Erji,Wang Chong,Wang LingxiaoORCID,Qiao Yongping,Shi Jianzong,Zhang Yuxin,Gao Junqiang,Wang YuanweiORCID,Li YanORCID,Yu Wenjun,Zhou Huayun,Xing Zanpin,Xiao Minxuan,Yin Luhui,Wang Shengfeng

Abstract

Abstract. Permafrost has been warming and thawing globally, with subsequent effects on the climate, hydrology, and the ecosystem. However, the permafrost thermal state variation in the northern lower limit of the permafrost zone (Xidatan) on the Qinghai–Tibet Plateau (QTP) is unclear. This study attempts to explore the changes and variability in this permafrost using historical (1970–2019) and future projection datasets from remote-sensing-based land surface temperature product (LST) and climate projections from Earth system model (ESM) outputs of the Coupled Model Intercomparison Project Phase 5 and 6 (CMIP5, CMIP6). Our model considers phase-change processes of soil pore water, thermal-property differences between frozen and unfrozen soil, geothermal flux flow, and the ground ice effect. Our model can consistently reproduce the vertical ground temperature profiles and active layer thickness (ALT), recognizing permafrost boundaries, and capture the evolution of the permafrost thermal regime. The spatial distribution of permafrost and its thermal conditions over the study area were controlled by elevation with a strong influence of slope orientation. From 1970 to 2019, the mean annual ground temperature (MAGT) in the region warmed by 0.49 ∘C in the continuous permafrost zone and 0.40 ∘C in the discontinuous permafrost zone. The lowest elevation of the permafrost boundary (on the north-facing slopes) rose approximately 47 m, and the northern boundary of discontinuous permafrost retreated southwards by approximately 1–2 km, while the lowest elevation of the permafrost boundary remained unchanged for the continuous permafrost zone. The warming rate in MAGT is projected to be more pronounced under shared socioeconomic pathways (SSPs) than under representative concentration pathways (RCPs), but there are no distinct discrepancies in the areal extent of the continuous and discontinuous permafrost and seasonally frozen ground among SSP and RCP scenarios. This study highlights the slow delaying process of the response of permafrost in the QTP to a warming climate, especially in terms of the areal extent of permafrost distribution.

Funder

National Natural Science Foundation of China

Ministry of Science and Technology of the People's Republic of China

Publisher

Copernicus GmbH

Subject

Earth-Surface Processes,Water Science and Technology

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