Density stratification of a meromictic lake on the Tibetan Plateau and its response to water level increase

Abstract Most endorheic lakes on the Tibetan Plateau (TP) have expanded rapidly since the late 1990s, causing significant impact on the regional eco‐environment. While changes in lake storage have been extensively investigated, the limnological processes in response to this rapid growth remain unclear. Based on eight times of in situ observations between 2009 and 2025, we analysed changes in stratification of Dagze Co, a meromictic lake on the central TP. Over the past 16 years, the lake level increased cumulatively by 6.5 m, accompanied by a decrease in salinity in both the epilimnion (from 14.8 to 12.3 psu) and hypolimnion (from 19.4 to 17.3 psu). Although the epilimnion thickness fluctuated significantly, its absolute position shifted upwards with the rising water level. The hypolimnion was less affected by lake level increase due to the persistent density gradient. Consequently, the metalimnion thickened considerably, characterized by the expansion of both thermocline and chemocline. A secondary density stratification emerged following an abrupt lake‐level increase in 2017–2018, which more than doubled the metalimnion thickness. The secondary stratification weakened but persisted in subsequent years, with the upper boundary of chemocline descending by ~7.0 m from 2018 to 2023. Our results indicate that climate change and the rapid lake expansion have significant impact on the stratification regime of lakes on the TP. More attention should be paid to understanding the responses of lake ecosystems to changes in salinity and stratification.