Gao Youhong, Zhang Hucai, Zhang Xiaonan, Duan Lizeng, Lei Guoliang, Pu Yang, Li Huayong, Li Haoyu, Liu Fengwen, Ashraf Umar, Anee Aqsa
Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, Yunnan 650500, China.
Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, Yunnan 650500, China; Southwest United Graduate School, Kunming 650500, Yunnan, China.
Sci Total Environ. 2024 Jan 1;906:167702. doi: 10.1016/j.scitotenv.2023.167702. Epub 2023 Oct 11.
The lake-level highstands on the southern Tibetan Plateau (TP) during the Early-Middle Holocene have traditionally been attributed to increased monsoonal precipitation. However, there has been limited discussion and evaluation regarding how the elevated shoreline indicates the formation of mega-paleolakes and the effects of glacial meltwater on rising lake levels. In this study, we conducted an investigation into the well-preserved paleoshorelines of Rinqen Shubtso, a closed-basin lake system located on the southern TP. By utilizing C dating and analyzing shoreline elevations, the Holocene lake-level fluctuation history of Rinqen Shubtso was reconstructed. Through examining strontium (Sr/Sr) and oxygen isotopes (δO), as well as Rb/Sr ratios in tufa samples from the shoreline, we evaluated the relative contribution of glacial meltwater and East Asian Monsoon precipitation to the lake-level expansion throughout this period. Our findings indicate that prior to 8.5 cal ka BP, the lake level reached its highest elevation before experiencing a rapid drop by approximately 44 m within a short timeframe. Subsequently, maintaining a stable highstand between 8.5 and 5.8 cal ka BP before gradually declining to its present elevation thereafter. We argue that the glacial meltwater induced by rising temperature due to solar insolation likely played a significant role in contributing to these large amplitude high lake levels prior to 8.5 cal ka BP, whereas the maximum East Asian Monsoon precipitation was responsible for sustaining high water levels during 8.5-5.8 cal ka BP when the mean latitudinal position of the summer Intertropical Convergence Zone shifted northward until reached its northernmost point at 8.5 cal ka BP. Following 5.8 cal ka BP, with the weakening of summer monsoon precipitation observed, gradually decreased lake level occurred accordingly. Our results provide valuable insights into understanding past changes in lake level, which are of great importance to predicting future lake variations on the TP.
青藏高原南部早-中全新世的湖面高水位传统上被归因于季风降水增加。然而，关于高海拔湖岸线如何指示巨型古湖的形成以及冰川融水对湖面上升的影响，相关讨论和评估有限。在本研究中，我们对位于青藏高原南部的一个封闭盆地湖泊系统仁青休布错保存完好的古湖岸线进行了调查。通过利用碳年代测定并分析湖岸线海拔，重建了仁青休布错全新世湖面波动历史。通过检测来自湖岸的凝灰岩样本中的锶（Sr/Sr）和氧同位素（δO）以及铷/锶比值，我们评估了冰川融水和东亚季风降水在这一时期湖面扩张过程中的相对贡献。我们的研究结果表明，在距今8500年校准年前，湖面达到最高海拔，之后在短时间内迅速下降了约44米。随后，在距今8500年至5800年校准年之间保持稳定的高水位，此后逐渐下降至当前海拔。我们认为，太阳辐射导致温度上升所引发的冰川融水，可能在距今8500年校准年前促成这些大幅度的高湖面水位方面发挥了重要作用，而东亚季风降水最多时则在距今8500年至5800年校准年期间维持了高水位，当时夏季热带辐合带的平均纬度位置向北移动，直至在距今8500年校准年到达最北点。在距今5800年校准年之后，随着夏季风降水减弱，湖面水位相应逐渐下降。我们的研究结果为理解过去的湖面变化提供了有价值的见解，这对于预测青藏高原未来的湖泊变化至关重要。
