Wednesday, 21 March 2012

Glacial Meltdown and Glacial Lake Outburst Floods

The scale of glacial melting on the west Rongbuk Glacier between 1921 and 2008. (Courtesy: RGS & David Breashears/GlacialWorks)
     
The Tibetan Plateau holds the Hindu-Kush Himalayan Ice Sheet, considered the largest ice mass outside the two poles. Hence scientists and geologists are increasingly using the name ‘Third Pole’ to pronounce the global significance of Tibet’s environment.

According to the Inter-governmental Panel on Climate Change (IPCC), glaciers in the Tibetan Plateau are receding fast, which will result in massive flooding followed by severe drought. Some reports suggest that Tibet’s glaciers have shrunk by 6,600 sq. km in the past 40 years and 82% of the glaciers have already retreated in the past 50 years. Furthermore, a major concern is the lack of any net accumulation of snow since 1950 over these mountains.

The scale of glacial melting can be viewed at Rongbuk Glacier, the northern slope of Mt. Everest (Tib: Jhomolangma). Between 1966 and 1997, the glacier receded by up to 270m in the middle, 170m at its eastern side, and 230m at its far-east side. Similarly, the Zepu glacier of southeast Tibet has thinned by more than 100m in the last three decades alone.

Mountain glaciers are experiencing less accumulation of snow and higher rates of melting. Without these glaciers the flow of rivers would become seasonal, leaving the livelihoods of hundreds of millions of people affected by the extreme weather conditions.

Furthermore, melting of glaciers and the permafrost in recent years have destabilized hillsides and resulted in landslides. A massive landslide in Tibet blocked Pareechu, a tributary of the Sutlej in Tibet. In the year 2000 and 20005 this unstable rock-fall dam burst caused heavy destruction of livelihood, infrastructure, and socio-economic assets in Kinnaur and Shimla districts in Himachal Pradesh, India.

Due to the rapidly melting glaciers, there has been a rapid increase in the numbers of glacial lakes in the Himalayan regions resulting in Glacial Lake Outburst Floods (GLOF) particularly in Nepal, India and Bhutan. According to the International Centre for Integrated Mountain Development (ICIMOD), there are 8790 glacial lakes within a selected area of Hindu-Kush Himalaya and more than 200 potentially dangerous Glacial lakes, where rock walls created by retreating glaciers may suddenly collapse.





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