Accelerating thermokarst lake changes on the Qinghai–Tibetan Plateau

www.nature.com/scientificreports OPEN Accelerating thermokarst lake changes on the Qinghai–Tibetan Plateau Guanghao Zhou 1, Wenhui Liu 1*, Changwei Xie 2, Xianteng Song 3, Qi Zhang 1, Qingpeng Li 1, Guangyue Liu 2, Qing Li 1 & Bingnan Luo 1 As significant evidence of ice-rich permafrost degradation due to climate warming, thermokarst lake was developing and undergoing substantial changes. Thermokarst lake was an essential ecosystem component, which significantly impacted the global carbon cycle, hydrology process and the stability of the Qinghai–Tibet Engineering Corridor. In this paper, based on Sentinel-2 (2021) and Landsat (1988–2020) images, thermokarst lakes within a 5000 m range along both sides of Qinghai–Tibet Highway were extracted to analyse the spatio-temporal variations. The results showed that the number and area of thermokarst lake in 2021 were 3965 and 4038.6 ha (1 ha = 10,000 m2), with an average size of 1.0186 ha. Small thermokarst lakes (<1 ha) accounted for 85.65% of the entire lake count, and large thermokarst lakes (>10 ha) occupied for 44.92% of the whole lake area. In all subregions, the number of small lake far exceeds 75% of the total lake number in each sub-region. R1 sub-region (around Wudaoliang region) had the maximum number density of thermokarst lakes with 0.0071, and R6 sub-region (around Anduo region) had the minimum number density with 0.0032. Thermokarst lakes were mainly distributed within elevation range of 4300 m–5000 m a.s.l. (94.27% and 97.13% of the total number and size), on flat terrain with slopes less than 3 ◦ (99.17% and 98.47% of the total number and surface) and in the north, south, and southeast aspects (51.98% and 50.00% of the total number and area). Thermokarst lakes were significantly developed in warm permafrost region with mean annual ground temperature (MAGT) > − 1.5 ◦ C, accounting for 47.39% and 54.38% of the total count and coverage, respectively. From 1988 to 2020, in spite of shrinkage or even drain of small portion of thermokarst lake, there was a general expansion trend of thermokarst lake with increase in number of 195 (8.58%) and area of 1160.19 ha (41.36%), which decreased during 1988– 1995 (− 702 each year and − 706.27 ha/yr) and then increased during 1995–2020 (184.96–702 each year and 360.82 ha/yr). This significant expansion was attributed to ground ice melting as rising air temperature at a rate of 0.03–0.04 ◦C/yr. Followed by the increasing precipitation (1.76–3.07 mm/yr) that accelerated the injection of water into lake. The Qinghai–Tibet Plateau is the highest and most widely distributed plateau permafrost on Earth, which is one of the most sensitive areas to climate change. The permafrost area is about 1.06 × 106 km21, and the ground ice volume in permafrost is 12,700 k m32. Due to climate warming, permafrost on the Qinghai–Tibet Plateau is warming and degradating characterized by rising mean annual ground temperature (MAGT) and increasing active layer thickness (ALT). The MAGT at 6 m depth have increased by about 0.43 ◦ C from Touerjiu Mountains to Fenghuo Mountain during the past decade3. The permafrost along the Qinghai–Tibet Highway (QTH) is significantly degraded than in other regions, resulting in an increasing ALT. The averaged increase rate of ALT is 7.5 cm/yr, with a range of 2.1–16.6 cm/yr during the past decade on the Q TH3,4. Thermokarst is one of the most common manifestations of permafrost degradation, and the ice-rich permafrost thawing leads to surface collapse. This can substantially affect global h ydrology5, global carbon e missions6,7, and infrastructure s tability8. Thermokarst lake is one of the most obvious characteristics of the thermokarst landform, which is widely distributed in the permafrost region of the Qinghai–Tibet Plateau. Thermokarst lake, also called thaw lake, tundra lake, thaw depression, or tundra pond9, refers to a body of shallow freshwater. Thermokarst lakes in permafrost 1 Department of Geological Engineering, Qinghai University, Xining 810016, Qinghai, China. 2Cryosphere Research Station on the Qinghai‑Tibet Plateau, State Key Laboratory of Cry‑osphere Sciences, Northwest Institute of Eco‑Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China. 3Xining Center for Integrated Natural Resources Survey, China Geological Survey, Xining 810000, Qinghai, China. *email: Scientific Reports | (2024) 14:2985 | https://doi.org/10.1038/s41598-024-52558-7 1 Vol.:(0123456789) www.nature.com/scientificreports/ regions across the Arctic have shrunkwith significant decrease in number and area over the past d ecade10,11. In western Alaska, the expansion of the thermokarst lake occurred parallel to the drainage. Drainage events always occurred in lakes larger than 1 ha (1 ha = 10,000 m2), and the area decreased by approximately 151.8 km2 between the 1970s and 2010s. However, small and medium lakes have increased in size by 119.9 km2 due to drainage from large lakes12. The thermokarst lakes on the Qinghai–Tibet Plateau have presented an expansionary trend, and the number of thermokarst lakes in the Beilu River Basin increased by 534, and the size increased by 4.1 km2 between 1969 and 201013. About 250 thermokarst lakes were distributed along the Qinghai–Tibet Railway between Kunlun Mountain and the Fenghuo Mountain, with a total area of about 139 × 104 m214. Thermokarst lake plays an essential role in the ecological environment and infrastructure stability. The permafrost region covers a quarter of the Northern Hemisphere land area with the largest land organic carbon15. Abrupt permafrost thawing accelerates organic carbon pool decomposition and releases greenhouse gases (CO2 and CH4)16,17. By analysis of the modeling studies, the amount of carbon released into the atmosphere by the thermokarst lake could double by the end of the c entury18. In addition, organic matter dissolved in thermokarst lake can have significant effects on the diversity and metabolism of bacterial communities, which further increase carbon emissions from permafrost19. The thermokarst lake also has an important influence on the stability of the QTH. Lateral thermal erosion causes the permafrost temperature to rise, resulting in subgrade subsidence, deformation, and c racks20. Thermokarst lakes were mainly small sizes with high dense distribution on the Qinghai–Tibet Plateau, so high-resolution images are required to accurately extract thermokarst lake accurately. Thereby, many previous studies on thermokarst lake were mainly limited to small region due to hard obtention of high-resolution image13, which was not beneficial to the study of the large-scale spatial distribution and influencing factors of thermokarst lake. So, the freely available Sentinel-2 (S2) images were essential to analyze thermokarst lakes along the QTH, which provided better understand of permafrost degradation in response to future climate and environmental changes. The purpose of this study are (...truncated)