LAUSR

Glacier-fed lakes on the Tibetan Plateau (TP) have undergone rapid expansions since the late 1990s, concurrent with the changing climate. However, the dominant cause(s) of lake area increases is still debated. To identify the drivers of lake expansion, we studied Aweng Co, a glacier-fed lake in the western TP, where surface area has increased (0.74 km 2  year −1 ) since the late 1970s and most rapidly (0.998 km 2  year −1 ) since the late 1990s. A water balance model was used to clarify the reasons for increased lake water volume, supported by stable isotope hydrology and the δ 18 O change recorded in recent sediments. Results showed that glacial meltwater probably had the biggest impact on changes in Aweng Co lake level in recent decades, but that precipitation was also an important contributor. Our study shows that δ 18 O of carbonate (δ 18 O carb ) has great potential for indicating source changes of water supply in such lakes, but there is a need to be cautious when interpreting δ 18 O carb due to the influence of multiple hydrological factors, which can change in dominance over time.