Reviewed by: Dr John Sweeney, National University of Ireland Maynooth, Ireland
Glacial lakes are a common feature of the Himalaya in general and the Khumbu Himal region of eastern Nepal in particular. In some of these glacial lakes, water is impounded by moraines. Such lakes where water is stored by moraines are in general hazardous. Outburst floods from such lakes are characterized by extraordinary peak discharges at the onset of the event and entrainment of large quantities of debris. Such lakes appear to be the most common type of glacial lakes now found in Nepal (Yamada and Sharma, 1993).
Glaciers are a key indicator of climate change as they react sensitively to climate (Oerlemans, 1994). The mean annual air temperatures rose rather dramatically in the 20th century (IPCC, 2001). This has most likely caused increasing glacier retreat in many parts of the world. A recent review of glaciers around the world shows that the average loss of length is about 10 meters (m) per year, and this pace is accelerating in many regions ( Lemke et al, 2007).
The case study on the development and climate change in Nepal from Shardul et al., 2003 reveals a significant warming trend in recent decades and are even more evident at higher altitudes. Similarly, Shrestha et al. (1999) also reported, a drastic warming over the last two decades in Nepal.
Climate change scenarios for Nepal across multiple general circulation models meanwhile show the average increase in the mean temperature by1.2°C and 3°C for 2050 and 2100 respectively (Shardul et al., 2003). Similarly, New et al., 2009 shows that temperature extremes will increase by up to 55% (2060s) and 70% (2090s) (http://www.kathmandutocopenhagen.org). This warming trend is likely to have significant impact on Nepal Himalayas- most significantly in terms of glacier retreat and significant increases in the size and volume of glacial lakes, making them more prone to Glacial Lake Outburst Flooding (GLOF). Though the data on the glacier mass balance provides the quantitative information on the increasing or decreasing of glacier, it is rare in the Himalayas of Nepal. However, over the past 30 years, the vast majority of all Himalayan glaciers have been retreating and thinning, with accelerated losses in the last decade (Bajracharya and Mool 2009). A number of recent research (e.g., Fujita et al., 2001; Bajracharya and Mool. 2009) have reasoned climate change as a driver to this decrease in mass balance of Himalayan glacier.
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