Scientists reveal climate impact on Qinghai-Tibet Plateau lakes

Recent research by Chinese scientists highlights the significant effects of global climate change over the past 36 years on the lakes of the Qinghai-Tibet Plateau, including expansion, increased water temperature, and greater transparency.

The findings were published on Tuesday in the prestigious international journal Nature Reviews Earth & Environment by the Tibetan Plateau Research Institute of the Chinese Academy of Sciences.

The research team discovered that alongside changes in lake water volume, there was a gradual decrease in salinity, a significant reduction in chlorophyll-a levels, and enhanced microbial diversity and nutrient status.

"These changes have, in turn, affected local climate and livelihoods, leading to increased regional precipitation and posing risks of lake overflow and breaching to infrastructure, living conditions and pastoral areas," said Jyu Jianting, co-lead author and associate professor at the institute.

This study is the first to systematically quantify the long-term evolution of the physical, chemical and ecological characteristics of lakes on the Qinghai-Tibet Plateau, providing essential scientific evidence for evaluating regional water security and carbon cycling.

The study found that over the past 36 years, the area of the lakes expanded by 26 percent, the water volume increased by about 170 cubic kilometers, and water transparency improved by 72 percent.

According to Zhu Liping, corresponding author and researcher at the institute, the lakes on the Qinghai-Tibet Plateau store about 70 percent of the liquid freshwater resources of the Asian Water Tower, directly influencing the water cycles of major rivers like the Yangtze and Yellow Rivers.

From 1986 to 2022, the total area of lakes larger than one square kilometer on the plateau increased from 37,000 square kilometers to 47,000 square kilometers, with water storage increasing by 169.7 cubic kilometers, equivalent to 3.8 times the maximum capacity of the Three Gorges Reservoir.

"While the expansion of lakes has temporarily improved water quality, it could trigger a series of ecological chain reactions in the long run, potentially threatening infrastructure safety," Zhu said.

The research shows that although rising water temperatures have enhanced phytoplankton activity, the carbon dioxide flux of the lakes has exhibited complex changes: during the 2000s, 2010s and 2020s, the plateau lakes released 16, 68.7, and 11.6 gigatons of carbon to the atmosphere respectively, with emissions from high-salinity lakes being three times greater than those from freshwater lakes.

"This challenges the traditional understanding that cleaner lakes are not necessarily carbon sinks," Zhu said, explaining that the interchanging roles between temperature and salinity have dynamically shifted the plateau lakes between carbon sources and sinks.

"The changes in the plateau lakes are a product of global warming," Jyu said. "The exact impact of lake changes on global warming, whether it will result in carbon release or absorption, remains a topic of significant debate requiring further research, enhanced observation, and the development of physical balance models."

According to the simulations from an empirical model, if industrial gas emissions like CO2 remain high, the Qinghai-Tibet Plateau's lake area could grow by an additional 8,000 to 9,000 square kilometers by 2050, equivalent to the volume of 11 Qinghai lakes.

"Although larger lake areas can help regulate local climate through increased precipitation, the ongoing expansion of closed lakes poses two significant risks: overflow and breaching threatening infrastructure like the Qinghai-Tibet Railway, and chronic salinity reduction potentially altering existing carbon exchange patterns and exacerbating regional carbon emission fluctuations," Jyu noted.

The research team recommended developing clear-physical-mechanism models for lake water balance, improving future prediction accuracy, and conducting all-season in situ observations. Establishing high-precision remote sensing systems and dynamic monitoring networks for lake-atmosphere carbon exchange is also essential.

As the second Tibetan scientific expedition progresses, researchers are integrating drone aerial surveys with satellite remote sensing, aiming to establish a real-time monitoring system in the future, thereby equipping the Asian Water Tower with an ecological early warning system, or a smart eye.