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Nature reflects our nature
photo and field observation and identified clear morphological changes suggesting glacier variation in the region during various stages in the past . When they compared the 1992 glaciers with those of 1958 in the area it was revealed that out of 57 glaciers , 50 % of them had retreated in the period from 1958 to 1992 . Also , 30 % of the glaciers were under stationary conditions and 12 % were advancing . Kayastha and Harrison ( 2008 ) studied changes in the equilibrium line altitude ( ELA ) since the Little Ice Age ( LIA ) in eastern Nepal using inventory data ( Asahi , 1999 , and personal communication from K . Ashai , 2003 ). They studied the shifting of the ELA of 113 debris-free glaciers in Kanchanjunga , Khumbu , Rolwaling ( including Shorong Himal ), and Langtang Regions and found that the ELAs shifted up between the end of the LIA and 1992 and between 1959 and 1992 ; in eastern Nepal were 79 and 25 m , respectively .
3.2 Khumbu Region
Khumbu Glacier is a large debris-covered valley glacier in the Khumbu Region , about 15 km long , which drains mainly from the West Cwm between Mt . Everest and Lohtse . The bare ice zones ( ice pinnacles ) in the glacier are gradually shrinking ( Seko et al ., 1998 ). The surface of the glacier lowered about 10 m throughout the debriscovered ablation area in the period 1978-1995 ( Kadota et al ., 2000 ). Indication of slowing down of ice flow was also detected which means the shrinkage may accelerate even if the ablation condition remains unchanged . Naito et al . ( 2000 ) developed a model coupling mass balance and flow dynamics of debris-covered glaciers and applied it to Khumbu Glacier . The model predicts the formation and enlargement of depression in the lower ablation area about 5 km upstream of the terminus . This depression could transform into a glacial lake in the future .
Yamada et al . ( 1992 ) reviewed terminus fluctuations of seven clean type glaciers in Khumbu for the period 1970s- 1989 . The majority of glaciers have retreated in the range of 30 to 60 m in the observed period .
The Institute of Research for Development ( IRD ) France studied the glacier mass balance of Mera Glacier in the Hinku Valley , Khumbu region since 2007 . They also installed an automatic weather station and collected meteorological data since 2011 . The mass budget of Mera Glacier ( 5.1 km2 in 2012 ), located in the southern part of this region , was balanced during 2007 – 15 , whereas Pokalde ( 0.1 km2 in 2011 ) and West Changri Nup glaciers ( 0.9 km2 in 2013 ), ∼30 km further north , have been losing mass rapidly with annual glacier-wide mass balances of −0.69 ± 0.28 m w . e . a−1 ( 2009 – 15 ) and −1.24 ± 0.27 m w . e . a−1 ( 2010 – 15 ), respectively . Sherpa et al . ( 2017 ) also studied these glaciers and found still negative mass balances .
3.3 Shorong Himal
Glacier AX010 in the Shorong Himal ( 27o 42 ’ N , 86o 34 ’ E ) is one of the most studied glaciers in Nepal . Changes in glacier terminus have been monitored from 1978 to 2004 . The aerial extent of the glacier was measured intermittently in 1978 , 1996 , and 1999 by the topographic survey ( Fujita , 2001 ). The terminus retreat from 1978 to 1989 was 30 m ( -2.7 m a-1 ), which is equivalent to 12 m thinning of the glacier surface . Similarly , the terminus retreat rates from 1989 to 1995 , 1996 to 1999 , and 1999 to 2004 were -6.7 m a-1 , -30 m a-1 , and -14 m a-1 , respectively .
3.4 Langtang Region
Yala and Lirung Glaciers are the most studied glaciers in the Langtang region . Several glaciological , hydrological , and meteorological investigations have been carried out on Yala Glacier and the Langtang Valley by Japanese scientists in the name of Glaciological Expedition in Nepal ( GEN ) which was started since the 1970s in Nepal . Regarding the researches on Lirung Glacier , the transverse profile of Lirung Glacier with debris-covered lower part was surveyed in 1987 and 1989 . There is no major change in the profile , however , photographs taken at different times show a clear retreat of the glacier . There is an indication that the upper step part and lower flatter part will separate in near future . Glaciological and meteorological studies are carrying out on Yala Glacier and Kyangjing by the Institute for Tibetan Plateau Research ( ITP ), Chinese Academy of Science ( CAS ), Beijing , China with collaboration with the Department of Hydro-meteorology , Tribhuvan University ( TU ) since 2009 .
3.4.1 Yala Glacier
Yala Glacier is one of the most investigated glaciers in the Nepalese Himalayas . It is situated in the Langtang Valley inside the Langtang National Park in Rasuwa district , Central development region of Nepal ( 28o14 ’ N , 85o37 ’ E ). It is a plateau-shaped glacier with no debris on its surface . The highest and lowest altitudes and the area of the glacier
28 Year Book of Environmental Science