The ground ice melting has accelerated the lake expansion in the hinterland of the permafrost region on the Qinghai-Tibet Plateau

Abstract

Study region

The Zonag Lake-Yanhu Lake basin on the Qinghai-Tibet Plateau (QTP).

Study focus

The melting of ground ice near the permafrost table is an important factor leading to the lake expansion on the QTP. We quantitatively assessed the contribution of change in ground ice to lake expansion in the Zonag Lake-Yanhu Lake basin using interferometric synthetic aperture radar monitoring.

New hydrological insights for the region

Two migration modes of meltwater from ground ice near the permafrost table were identified: one flows directly into the lake, while the other replenishes the active layer. From 2018–2021, the meltwater source of ground ice melting to the hydrological cycle was estimated at 0.04 ± 0.002 Gt/a, accelerating lake expansion (the rate of increase in lake water storage) by 9.8 %. Our findings also indicate that ground ice meltwater increases the soil moisture content of the active layer, with an estimated increase in equivalent liquid water thickness of approximately 0.002 Gt/a. This suggests that previous assessments of water released from ground ice melting, based on ground surface subsidence, may underestimated actual amounts by around 5 % in the permafrost regions. These findings emphasized that the hinterland permafrost region was also experiencing rapid degradation, and the melting of ground ice was accelerating lake expansion, providing valuable insights into the impacts of permafrost changes on the regional water cycle.