Global warming accelerates the upfreezing of permafrost in arid middle Tianshan Mountains

Abstract

Upfreezing is an important geomorphic process in the periglacial environment. It is a product of cold climate and thus an important part of the cryospheric processes. Based on the long-term positioning observations in the source area of the Urumqi River, this article represents an in-depth discussion of the characteristics of sorted circles and upfreezing mechanisms in the Tianshan Mountains. In the source area of the Urumqi River, the intensity of upfreezing is the highest within the top 25 cm near the surface, while targets with a diameter of 3 cm are least affected by upfreezing. There is no distinct difference between the centre with fine grains and the margin with coarse debris within the same sorted circle in terms of the intensity of upfreezing. The correlation analysis demonstrates that temperature plays an important role in upfreezing and the development of sorted circles. A long-time positioning observation of sorted circles reveals that periglacial landforms are sensitive to regional climate change and respond quickly to the temperature increase of the recent two decades. Enhanced upfreezing was found to be due to increased soil moisture content.

Climate change impacts and adaptation to permafrost change in High Mountain Asia: a comprehensive review

“…Sorg et al (2015) show synchronous activity of rock glaciers at decadal scale in Central Asia. Li et al (2013) show the formation of patterned ground in line with an expansion of soil moisture, most prevalent in the first 25 cm of soil. Zhong et al (2021) show deformation of thermokarst landforms around 3600 m between April 2016 and June 2018, finding a 3.4 m vertical change and 10.7 m wall retreat.…”

“…In the Tien Shan rising temperatures and soil moisture content in permafrost soils have caused upfreezing, a phenomenon where freezing leads to the movement of deposited materials towards the soil surface, and the development of sorted circles (Li et al 2013).…”

Contemporary Sorted Patterned Ground in Low Altitude Areas of Tasmania

“…These include the frost pull of coarse material (clasts) to the surface of a deposit and subsequent expansion of saturated fine material by up‐freezing and vertical heaving of the ground as a result of thermal expansion of ice lenses (Matsuoka and Ijiri, ; Peterson et al ., ). Coarse clasts are pushed out by the doming of the fines to create the stripes, polygons or circles (Boelhouwers et al ., ; Kessler and Werner, ; Peterson and Krantz, ; Li et al ., ). Differential melting and settlement based on density differences can enhance the process (e.g.…”