Holocene hydrological history of a Tibetan glacier-fed lake Taro Co in response to climate change

Abstract

Lake hydrological fluctuations on the Tibetan Plateau (TP) are highly sensitive to global climate change, which can be reconstructed directly by dating paleoshorelines representing past lake-levels. In this study, we reconstructed the Holocene lake-level history of Taro Co lake system (Taro Co, Zabuye Salt lake and Lagkor Co) on the southwestern TP, based on seventeen optically stimulated luminescence ages of paleoshorelines. The results showed that lake-levels were at the broad highstands of ∼40 m above modern lake-level (amll) from 11.6 to 7.0 ka, during which the three lakes were integrated and formed a mega paleolake. After 7.0 ka, the mega paleolake fluctuantly contracted, and Lagkor Co and Zabuye Salt Lake probably became separated at ∼6.9 and ∼3.4 ka, respectively. Seven rapid millennial low lake stands were identified at 11.3–11.2 ka (14 m amll), 9.9–8.7 ka (< 28 m amll), 8.2–7.9 ka (6 m amll), ∼6.9 ka (5 m amll), ∼3.0 ka (8 m amll), 2.1–1.1 ka (< 6 m amll) and ∼0.4 ka (6 m amll). The large magnitude lake-level declines indicated that they reflected effective moisture in response to global millennial-scale climate events, e.g., the 11.1, 10.3, 9.4, 8.2 and 7.2 ka events in the early and middle Holocene, and the 4.2 ka and Little Ice Age events in the late Holocene. Holocene lake-level fluctuations were simultaneous with that of other lakes on the south-central TP. Comparisons with other paleoclimatic records suggested that the Holocene hydrological history of Taro Co was mainly dominated by both monsoonal precipitation and glacial meltwater supply, as well as evaporation and basin topography. Differences in meltwater supply probably led to different lake-level change histories for endorheic lakes in the lake system. In the future warming and wetting, Tibetan endorheic lakes would keep expanding, hence Taro Co lake system would be formed again through hydrological connections.