Abstract:

The Mabucuo lake, located in the middle of the southern Tibetan valley, is sensitive to climate changes mainly because of that the lake is affected by the Indian summer monsoon and westerlies. Multi-temporal remote sensing images provide the characteristics of lake level fluctuation in recent years, reflecting the regional climate changes. The sediments of lake shorelines and lake terraces provide ideal materials for studying the changes of lake level, which is used to understand the history of regional paleoclimate and the fluctuations of lake level. Remote sensing and image interpretations, Accelerator Mass Spectrometry (AMS) ¹⁴C dating, and Digital Elevation Model (DEM) data were applied to investigate the elevation and the chronology of lake shorelines or lake terraces in the north part of the Mabucuo lake. Combining with the lake level changes by the sedimentary sequence of the lake terrace section, the lake level fluctuation of Mabucuo since Late Pleistocene is reconstructed. Period S₇-S₄, before 14,256-13,984 a BP, Mabucuo was a unified great lake with southern Galacuo and Duoqingcuo. The lake level of Mabucuo gradually decreased from S₇ to S₄ stage. Mabucuo, Duoqingcuo and Galacuo have been separated into three independent lakes. The lake level of Mabucuo gradually raised from S₄ to S₃ stage, and the separated lakes reunited to one great lake. This great lake only lasted a short time. Period S₃-S₁, after 14,256-13,984 a BP, Mabucuo had become an independent lake again. The lake level of Mabucuo gradually decreased from S₃ to S₁. In summary, the lake level of Mabucuo has experienced a process from high to low, then to high, and then to low since Late Pleistocene. The lake level was mainly controlled by regional atmospheric precipitation and glacier meltwater, which reflected the strength of Indian monsoon and the global climate change. During the last decade, the lake level of Mabucuo interpreted by the remote sensing evidence shows that Mabucuo has shrunk from 2013 to 2015 and expanded from 2016 to 2018, which reflected the trend of warm and humid climate in the middle of southern Tibetan valley. This study will be great significance to understand the trends of climatic and environmental changes in the Tibetan plateau.

Key words: Tibetan plateau, Mabucuo Lake, remote sensing image, lake shoreline, lake level, climate change