Holocene lake level fluctuations and environmental changes at Taro Co, southwestern Tibet, based on ostracod-inferred water depth reconstruction

Abstract

Lake level change is an important indicator of changes in the hydrological status of lakes triggered by the influence of atmospheric circulation systems. Previous studies show that the interaction of the Indian monsoon and the Westerlies, and their influence on environmental changes in the Tibetan Plateau region, remain unclear. Here, we reconstruct the Holocene lake level history of a lake, Taro Co, in southwestern Tibet, based on the relationship between ostracod assemblages and water depth from 34 surface sediment samples spanning the depth range 0 to 125 m. Measurement and analysis of multi-proxy data from a 310 cm sediment core from Taro Co lead to the following conclusions: (1) From 10,200 to 9400 cal. a BP, the lake received large inflows of freshwater (mainly glacial melt water) resulting in a rapid rise in lake level. Following a cold and dry interval and low lake level from 9400 to 8800 cal. a BP, the lake maintained a high level between 8800 and 7500 cal. a BP. This was followed by a less warm and wet period until 6400 cal. a BP. From 6400 to 1200 cal. a BP, the lake probably overflowed after reaching a high level, and after 1200 cal. a BP, the lake level decreased and fluctuated around the modern depth of 60 m at the coring site. (2) The region experienced warm and wet conditions from 10,200 to 6400 cal. a BP, with a cold event at around 9000 cal. a BP, which probably resulted from the influence of the Indian monsoon. However, the inferred wet conditions between 6400 and 1200 cal. a BP are not observed in other records from the monsoon region; they are consistent with numerous records from the regions under the influence of the Westerlies, which probably indicate an interval of Westerlies-domination in the Taro Co region.