Chinanews.com, April 4 (Reporter Sun Zifa) How does global warming affect the loss of underwater ice in Himalayan ice lakes? New research led by Chinese scientists and conducted in collaboration with international counterparts found that the mass loss of about 3.2000 billion tons of underwater ice in the Himalayas was underestimated between 2020 and 27.
This important achievement paper on global climate change research was jointly completed by the scientific expedition team of the second Qinghai-Tibet scientific expedition in China "Dynamic Change and Impact of Water Towers in Asia", researcher Zhang Guoqing of the environmental change and multi-circle process team of the Institute of Tibetan Plateau Research, Chinese Academy of Sciences, and researchers from the Graz University of Technology in Austria, the University of St. Andrews in the United Kingdom and Carnegie Mellon University in the United States, and was published online in the international professional academic journal Nature Geoscience on the night of April 4, Beijing time.
A glacial lake on the Qinghai-Tibet Plateau – Galon Error. Photo courtesy of the Tibetan Plateau Institute, Chinese Academy of Sciences
Zhang Guoqing, the first author and co-corresponding author of the paper, said that digital elevation models (DEMs) are widely used to estimate global glacier mass loss, but the method can only observe the glacier surface and water surface, and cannot reveal the glacier mass loss that occurs below the water surface of preglacial lakes.
In the context of global warming, glaciers are retreating and retreating at an accelerated rate. The Himalayan region is home to tens of thousands of glacial lakes, and the preglacial lakes connected to glaciers are expanding rapidly, accounting for about 12% of the total number of glacial lakes in the region. Previous studies have focused more on changes in the size and volume of glacial lakes and the resulting risk of glacial lake outburst flooding. However, when estimating changes in glacier ice quantity, traditional geodesy methods do not take into account the loss of underwater ice mass caused by the expansion of glacial lakes, resulting in underestimation of glacier mass loss in the Himalayan region and even on a global scale.
He pointed out that in this study, Chinese and foreign scientists used the remote sensing data of glacial lakes in multiple years to map and classify glacial lakes in the Himalayan region in detail, combined with the underwater topographic measurement data of typical glacial lakes, estimated the water volume changes of Himalayan glacial lakes in detail, and quantified the loss of glacier mass under the surface of glacial lakes due to climate warming.
The findings show that between 2000 and 2020, the number of glacial lakes in the Himalayas increased by about 47%, the area expanded by 33%, and the water volume increased by 42%. The increase in the volume of glacial lakes led to an underestimation of about 2000.2020 billion tonnes of underwater ice mass loss in the Himalayas between 27 and 6, accounting for about 5.12% of the total mass loss in preglacial lakes, with the Central Himalayas being the most undervalued, with about 10.5 billion tonnes, or 200%. Located in the Poqu River basin in the central Himalayas, Galonco covers an area of about 65 square kilometers, with a maximum depth of 2100 meters and a loss of 12% of underwater ice mass. At the same time, the study also preliminarily estimated the global loss of underwater ice in preglacial lakes, which is about <> billion tons, accounting for <>% of the global total glacial lake contact glacier mass loss.
Underestimation of Himalayan underwater ice mass loss in 2000~2020. Photo courtesy of the Tibetan Plateau Institute, Chinese Academy of Sciences
Zhang Guoqing said that as glacial lakes in the Himalayas become larger and deeper, underwater ice loss remains an important factor affecting future total glacier mass loss and related glacial lake outburst flood risk assessment. Their latest research provides methods to quantify underwater ice mass loss, reduces the uncertainty of estimating total glacier mass loss, provides important data for glaciological models, and provides important scientific basis for more accurate simulation of past and future glacier mass balances, and assessment of glacier and glacial lake hazards and changes in water resources. (End)