Late Quaternary hydrological changes inferred from lake level fluctuations of Nam Co (Tibetan Plateau, China)

Abstract

This paper discusses the range of lake level changes, using hydro-acoustic techniques and sediment core data for Lake Nam Co in Central Tibet (China). This second largest Tibetan lake is situated at an elevation of 4718 m a.s.l. Lake level changes with different high stands documented by beach remnants are widespread on the Tibetan Plateau and also in Lake Nam Co. They indicate significant changes in the hydrological system triggered by the monsoonal circulation. Using hydro-acoustic techniques submerged beach remains at approximately 10/15 m, 30 m, 45 m, 70 m and 95 m below present day lake level were detected, indicating a more negative water balance than today. The −10/−15 m lake level is dated to an age equal to the Little Ice Age. All deeper lake levels are assumed to have been formed prior to ∼10000 cal BP. Folded older sediments, detected in the hydro-acoustic profiles indicate a possible larger extent of the glaciers during or prior to the Last Glacial Maximum (LGM). This is followed by a low stand or even by possible desiccation of the entire lake basin during or after the LGM.