Scentific Research

In the context of accelerating retreat of most glaciers in Tibetan Plateau due to global warming, the glaciers in the Karakoram Mountains in Xinjiang China and northern Pakistan unexpectedly maintain stable or gain in mass under westerlies in the last dozen years, a phenomenon known as "Karakoram Anomaly".

Periodic glacier surges (rapid advancing of glaciers) in the region block rivers frequently, making the Karakoram Mountains one of the area most frequently stricken by glacial lake outburst floods (GLOF) in the world. Glacial activities are closely related with regional climate. To understand the evolution of the disaster chain of glacier-dammed lakes in the Karakoram Mountains under the background of future climate change, it is necessary to establish a case base with long time series to clarify its outbreak frequency on the centennial and interdecadal timescales. At the same time, it is an important scientific basis for formulating disaster prevention and alleviation strategies to demonstrate the quantitative/semi-quantitative relationship between the kinematic parameters of glaciers and ice dam formation and outburst processes and their scales. Due to the lack of long-sequence data on the disaster chain of glacier-dammed lakes, there are still few systematic researches on the above problems.

Recently, the team of Cui Peng, a Researcher of China-Pakistan Joint Research Center on Earth Sciences, documented and analyzed 179 GLOFs events that occurred from 1533 to 2020 in the Karakoram Mountains using remote sensing, field survey and historic records. The result shows two periods of increased GLOF generation between 1890-1930 and 1990-2019 (produced 70.7% GLOFs), and a decline between 1940 and 1970. The team extracted the interannual variations of the velocity of 10 typical river-blocking glaciers in the past 30 years, and documented a total of 19 glacier surges, which coincide with the timing of GLOFs in history. The results show that six surges of Khurdopin, Kyager and Shishper glaciers indicate a surge recurrence interval of 15-20 years. The researchers then analyzed the average daily variation of glacier velocity, and the results show that: the average velocity of the glacier during the calm period was only 79 m/y, and the glacier surge usually started in early spring, and the peak surge velocity may reach 320-350 m/y in just a few months (in late spring and summer). Then, the surge velocity would gradually decrease, which may last for several years. In the early stage of the surge, the glaciers have high velocity and high density of ice crevasses, which makes them easy to penetrate to form burst conduits, so the scale of the glacier-dammed lakes is small; in the stage of gradual reduction of surge velocity, the density of ice crevasses is low, and the burst conduits formed earlier can be resealed due to the ice dam collapse. At this time, the dammed body increases steadily and the water level of the dammed-lake increases as well, which can induce multiple outburst floods or even large-scale outburst floods. Based on the above-mentioned mechanism of glacier surge controlling the evolution of glacier-dammed lakes, a conceptual model for the evolution of glacier-dammed lakes is proposed, which provides first-hand scientific data and theoretical basis for the prediction and prevention of glacial damming disaster chains along the China-Pakistan Economic Corridor under the background of future climate change. At the same time, the GLOFs events of long-time scale also makes up for the lack of high-precision historical records of glacier movements, which can provide support for the research on glaciology.

Relevant findings were published in Earth-Science Reviews. Doctoral student Nazir Ahmed Bazai is the first author of the thesis, and Researcher Cui Peng is the corresponding author. The research was supported by the National Natural Science Foundation of China, the Second Tibet Plateau Scientific Expedition and Research Program, etc.

Fig. 1 The glacial lake outburst floods (GLOFs) events in five core areas of the Karakoram Mountains as well as time and frequency of major glacier damming and outburst floods