Insights into a remote cryosphere: a multi-method approach to assess permafrost occurrence at the Qugaqie basin, western Nyainqêntanglha Range, Tibetan Plateau

Abstract

Abstract. Permafrost as a climate-sensitive parameter and its occurrence and distribution play an important role in the observation of global warming. However, field-based permafrost distribution data and information on the subsurface ice content in the large area of the southern mountainous Tibetan Plateau (TP) are very sparse. Existing models based on boreholes and remote sensing approaches suggest permafrost probabilities for most of the Tibetan mountain ranges. Field data to validate permafrost models are generally lacking because access to the mountain regions in extreme altitudes is limited. The study provides geomorphological and geophysical field data from a north-orientated high-altitude catchment in the western Nyainqêntanglha Range. A multi-method approach combines (A) geomorphological mapping, (B) electrical resistivity tomography (ERT) to identify subsurface ice occurrence and (C) interferometric synthetic aperture radar (InSAR) analysis to derive multi-annual creeping rates. The combination of the resulting data allows an assessment of the lower occurrence of permafrost in a range of 5350 and 5500 m above sea level (a.s.l.) in the Qugaqie basin. Periglacial landforms such as rock glaciers and protalus ramparts are located in the periglacial zone from 5300–5600 m a.s.l. The altitudinal periglacial landform distribution is supported by ERT data detecting ice-rich permafrost in a rock glacier at 5500 m a.s.l. and ice lenses around the rock glacier (5450 m a.s.l.). The highest multiannual creeping rates up to 150 mm yr−1 are typically observed on these rock glaciers. This study closes the gap of unknown state of periglacial features and potential permafrost occurrence in a high-elevated basin in the western Nyainqêntanglha Range (Tibetan Plateau).

Rock glacier inventory of the western Nyainqêntanglha Range, Tibetan Plateau, supported by InSAR time series and automated classification

“…Large‐scale permafrost maps of the TP predict permafrost for most nonglaciated parts of the mountain range 66,67 . Field studies estimate a lower permafrost limit of 5,300–5,450 m in two north‐oriented catchments 68,69 . They identified a small number of rock glaciers displaying moderate velocities of 5–10 cm/yr 69 .…”

“…Field studies estimate a lower permafrost limit of 5,300–5,450 m in two north‐oriented catchments 68,69 . They identified a small number of rock glaciers displaying moderate velocities of 5–10 cm/yr 69 . Rock glacier inventories on the TP are rare, though one recently identified 295 rock glaciers in Daxue Shan, southeastern TP 13 .…”

Rock Glaciers

“…Holistic studies which combine the information from various remote sensing methods and insitu information obtained from geophysics and other measurements have the potential to provide new detailed insights into the characteristics and climate response of rock glaciers and other periglacial ice-debris landforms (Capt et al 2016;Bolch et al 2019;Buckel et al 2021;Halla et al 2021).…”

Contribution of ground ice melting to the expansion of Serling Co lake on the Tibetan Plateau

“…On steep slopes, the deformation occurs mainly as downslope movements driven by gravity (Buckel et al, 2021;Reinosch et al, 2020); thus, we considered only areas with slope angles below 10°. The threshold of 10° was adopted based on previous works (Reinosch et al, 2020;Buckel et al, 2021).…”

“…ii) masking off areas with the LOS direction periodic (seasonal) amplitudes or long-term velocities ≤2.5 mm The threshold of 2.5 mm was set based on previous works (Daout et al, 2017;Buckel et al, 2021). A periodic 295 seasonal threshold was used to mask off areas that are not affected by permafrost activity (because they do not experience periodic frost heave and thaw subsidence) but exhibit continuous sedimentary uplift or subsidence.…”