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Prevailing lake changes on the Qinghai–Tibetan Plateau (QTP) have occurred. Selin Co, a representative saline lake in the central region of the QTP, has had the largest increase and become the largest endorheic lake in Tibet, but the main cause for its dramatic expansion is still under debate. Based on Landsat images, meteorological data and glacier and permafrost data, the dynamic changes in Selin Co and its surrounding small lakes were systematically discussed, and the driving factors behind these changes were further explored. The results suggest that during 1988–2017, the areas of Bange Co and Cuoe Lake showed slow, overall increasing trends at the rates of 0.28 km2/year and 0.11 km2/year, respectively, and upward trends before 2005 but downward trends afterward. The area of Selin Co substantially increased by 685.8 km2 with a growth rate of 30.39 km2/year, with a slow increase of 27.11 km2 during the period of 1988–1997, a rapid increase of 510.53 km2 during 1997–2005 and an increase of 148.16 km2 during 2005–2017. Accordingly, the lake level and water volume of Bange Co slightly increased by 1.64 m and 0.088 km3, respectively, whereas those of Selin Co significantly rose by 8.138 m and 17.47 km3, respectively. The changes in the areas of Bange Co and Cuoe Lake were mostly related to annual precipitation (AP). The expansion of Selin Co may be partly explained as the discharge from the glacier retreat and permafrost degradation in the watershed. Glacial meltwater has enhanced owing to rising, with a rapid reduction of 165.1 km2 (39%) in the glacier area in the basin between 1980 and 2010. Permafrost degradation has significantly accelerated, with increases in the active layer thickness (ALT) (7.44 cm/year) and soil temperatures at a 15-m depth (0.0346 °C/year). [ABSTRACT FROM AUTHOR]

Lakes on the Qinghai–Tibetan Plateau (QTP) have experienced significant changes, especially the prevailing lake expansion since 2000 in the endorheic basin. The influence of permafrost thawing on lake expansion is significant but rarely considered in previous studies. In this study, based on Landsat images and permafrost field data, the spatial-temporal area changes of lakes of more than 5 km2 in the endorheic basin on the QTP during 2000–2017 is examined and the impact of permafrost degradation on lake expansion is discussed. The main results are that permafrost characteristics and its degradation trend have close relationships with lake changes. Lake expansion in the endorheic basin showed a southwest–northeast transition from shrinking to stable to rapidly expanding, which corresponded well with the permafrost distribution from island-discontinuous to seasonally frozen ground to continuous permafrost. A dramatic lake expansion in continuous permafrost showed significant spatial differences; lakes expanded significantly in northern and eastern continuous permafrost with a higher ground ice content but slightly in southern continuous permafrost with a lower ground ice content. This spatial pattern was mainly attributed to the melting of ground ice in shallow permafrost associated with accelerating permafrost degradation. Whereas, some lakes in the southern zones of island-discontinuous permafrost were shrinking, which was mainly because the extended taliks arising from the intensified permafrost degradation have facilitated surface water and suprapermafrost groundwater discharge to subpermafrost groundwater and thereby drained the lakes. Based on observation and simulated data, the melting of ground ice at shallow depths below the permafrost table accounted for 21.2% of the increase in lake volume from 2000 to 2016. [ABSTRACT FROM AUTHOR]