The lower limit of mountain permafrost in the Russian Altai Mountains

Permafrost‐indicator features, such as rock glaciers, pingos and ice‐wedge polygons, exist at many locations in and around the South Chuyskiy Range of the Russian Altai Mountains (∼50°N). The distribution of these features suggests that the altitudinal range of the sporadic/patchy permafrost zones and the widespread discontinuous/continuous permafrost zones are 1800–2000 m ASL and above 2000 m ASL, respectively. The lower limit of discontinuous permafrost is approximately 200 m lower than in the Mongolian Altai, which are at a similar latitude. Cold air drainage and/or temperature inversions during winter within U‐shaped valleys together with a thin snow cover because of low precipitation during the same season likely cause the lower permafrost limit in the study area. The calibrated 14 C ages of tree remnants found in a rock glacier front in the lower Akkol valley were 293 ± 21 years BP and 548 ± 21 years BP. Given the time of emergence from beneath the Sofiyskiy glacier, this rock glacier developed between 3800–2600 and 550 years BP.