Global warming serving up drinks without ice for rapidly expanding ‘Monster Lake’ in Tibet, new study suggests
Latest research by Chinese scientists seeks to demystify impact of global warming on largest and fastest-expanding lake in ‘Asia’s water tower’, claims glacial melt played minor role compared to rain and snow
The rapid expansion of Selin Co (“lake”) in Tibet has mainly been caused by rising levels of rain, snow and other forms of precipitation not glacial melt triggered by global warming as was otherwise presumed, according to a new study by Chinese scientists.
Selin Co in the northern Lhasa terrane is the largest body of water on the Tibetan Plateau. It ranked as the second-largest before the turn of the century, but a continued growth spurt has changed that while also spurring concerns about the earth’s rising temperature.
“Retreating glaciers are a problem in Tibet, but they are not to blame for everything,” said Professor Wang Lei, lead scientist of the study with the Chinese Academy of Sciences’ Institute of Tibetan Plateau Research in Beijing.
Selin means “monster” in Tibetan. According to local folklore, an evil spirit dwells at the bottom of the lake. But such tales are not what concerned Wang and his team.
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Since the mid-1970s, the lake’s surface area has grown by almost 40 per cent to more than 2,100 square kilometres.
Due to its high altitude and primitive landscape, the plateau is extremely sensitive to the impact of climate change. What happens there is considered an indication of similar changes that may take place elsewhere on the planet in the future.
Tibet is considered a “water tower” of Asia as the three largest rivers in China originate there. Any major change to water storage and distribution in the region would likely have a massive ecological and economic impact.
All of the major lakes on the central part of the Tibetan Plateau have increased in size since the 1990s.
Earlier studies have suggested glacial melt was largely responsible. These have been backed up by satellite imagery showing that the increasing size of the lakes is roughly equivalent to the shrinking size of nearby glaciers.
Yet other members of the scientific community maintain this is just a coincidence.
Wang’s team took a different approach. They tried to reconstruct the process by which the Selin lake expanded by taking into account its surrounding areas to determine the role played by various forces.
Using a new mathematical model and fresh data collected by local observatories, Wang’s team built the first comprehensive computer simulator to try and explain the lake’s growth.
Their findings were published in a paper in the latest issue of the journal Water Resources Research, which is part of the American Geophysical Union.
The digital simulation included most of the hydrological mechanisms that could possibly have affected the lake, such as wind, solar radiation and run-off from nearby waterways.
The researchers found that precipitation including water vapour such as drizzle, rain, sleet, snow, graupel and hail had contributed nearly 60 per cent of the lake’s surface expansion.
Only about 10 per cent derived from melted ice and snow, they said, adding that there were other contributing factors such as reduced solar radiation and slowing rates of evaporation in the area.
Wang’s team is not the first to challenge the theory that glacial melt is the predominant force behind the swollen lakes in the region.
Another research team from China studied six landlocked lakes in central Tibet two years ago and found their expansion was not related to shrinking glaciers.
But Wang said his team’s results could not be applied directly to other lakes in the region, or in Tibet as a whole.
“Using the same method to study other lakes in Tibet could yield different results,” he said.
“In some areas, the contribution of meltwater may dwarf other elements such as precipitation,” he added.
“Melting glaciers in Tibet is a serious issue. Neglecting the impact of this would be a big mistake,” he conceded.
Moreover, there were other limits to the team’s research.
For example, the observational data collected by local stations fell short of their expectations in terms of quantity, which in some cases could have compromised the results or resulted in uncertainty, they said.
The computer simulator also treated ice and snow as one and the same, even though they have different properties.
Wang said the accuracy of their simulation could be improved with further on-site observation, among other areas.
