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

Abstract

Abstract. Serling Co lake, surrounded by permafrost and glacier-occupied regions, has exhibited the greatest increase in water storage over the last 50 years among all the lakes on the Tibetan Plateau. However, increases in precipitation and glacial melting are not enough to explain the increased water volume of lake expansion. The magnitude of the contribution of thawing permafrost to this increase under climate warming remains unknown. This study made the first attempt to quantify the water contribution of ground ice melting to the expansion of Serling Co lake by evaluating the ground surface deformation. We monitored the spatial distribution of surface deformation in the Serling Co basin using the SBAS-InSAR technique and compared it with the findings of field surveys. Then, the ground ice meltwater volume in the watershed was calculated based on the long-term deformation rate. Finally, this volume was compared with the lake volume change during the same period, and the contribution ratio was derived. SBAS-InSAR monitoring during 2017–2020 illustrated widespread and large subsidence in the upstream section of the Zhajiazangbu subbasin, where widespread continuous permafrost is present. The terrain subsidence was normally between 5 and 20 mm/a, indicating rapid ground ice loss in the region. The ground ice meltwater reached 56.0 × 106 m3/a, and the rate of increase in lake water storage was 496.3 × 106 m3/a during the same period, with ground ice meltwater contributing 11.3 % of the lake volume increase. This study is especially helpful in explaining the rapid expansion of Serling Co lake and equilibrating the water balance at the watershed scale. More importantly, the proposed method can be easily extended to other watersheds underlain by permafrost and to help understand the hydrologic changes in these watersheds.

Estimating contribution of permafrost to lake expansion by SBAS-InSAR: a case study from Hohxil Lake basin in the Tibetan Plateau

“…Due to much water could be collected, the most of those uplifted points occurred in the basin, which was greater than the infiltration and evaporation of the basin, resulting in ground ice aggregation and then a long-term uplift of permafrost [24]. In addition, the rise of ground water level would also lead to the uplift phenomenon [57]. As shown in Fig.…”

“…As for the reason why the permafrost in the flat areas of the basin was generally uplifted, especially in the alluvial plain downstream of Malan glacier, it was likely that the surface runoff formed by summer rainfall and snow meltwater increased the soil water content, leading to the phenomenon that the make-up water of permafrost was greater than the lost water (e.g. evaporation and leakage) during the freeze-thaw cycle, finally resulting in ground ice aggregation and causing a long-term uplift [24,57]. Wang et al (2021) [57] also pointed out that the rise of groundwater table could trigger this type of uplift signals.…”