Late-Holocene hydrological variability from the NW Himalaya and southwestern Tibetan Plateau: Paleo-salinity records from Pangong Tso

Variations in lake-levels and hydrology are connected to climatic dynamics over the Trans-Himalaya and Tibetan Plateau (TP). Pangong Tso, a similar to 140 km long hypersaline lake, is sensitive to changes in air temperature, precipitation and snow-glacier melt over the southwestern TP. The incised tributaries entering the lake expose deltaic sequences constituting topset, foreset and bottomset. Sedimentology, chronology and diatom analysis of delta sediments; and stable isotopic and sclerochronological analysis of gastropods helped delineate the Late-Holocene variation in lake levels, surface temperature and salinity. The elevation of the topsets is considered as representing past lake high-stands from where molluscs were also recovered. Three phased lake level changes are observed during the past 3 ka. The first high-stand (+1.4-3.0 m) was at similar to 2.8-2.0 ka when lake surface salinity and temperature were 4.67-6.01 ppt (parts per thousand) and 5 degrees C-7 degrees C, respectively, against the modern average values of 7.7 +/- 0.09 ppt and 16.1 degrees C +/- 2.0 degrees C. Followed by a brief decline, another high-stand (+3.0-3.6 m) is observed at 1.1 ka when the salinity is reduced to 4.03-5.72 ppt and lake surface temperature to 5 degrees C8 degrees C. A corresponding increase in freshwater diatom concentration is also observed here. The third phase over the past 1 ka witnessed a fall of similar to 3.6-6 m in lake level that is attributed to an abrupt rise in aridity over the TP. We demonstrate that lake level variation in the region is a function of the variability of the Indian Summer Monsoon (ISM) and the westerlies, however during the high-stand, the hydrology of the lake was dominated by ISM precipitation.