12. Variability of Glaciers and Snow Cover

Impact of climate change on the Himalayan glaciers is debated extensively, as the IPCC report of 2007 suggested that the Himalayan glaciers are likely to disappear by 2037. This controversial prediction has led to large amount of scientific investigations. These investigations have produced significant amount of new data and information. Here, we propose to review all the new information published in recent years. Recently, numerous investigations have been carried out to estimate areal extent of glaciers in the Himalayas where the mean glacial extent is estimated at 24,697 ± 3260 km². In addition, the glacier-stored water is estimated at 2956 ± 1454 Gt. Glacier retreat is estimated by numerous investigations, and the mean loss for 83 glaciers for past four decades is estimated at 550 ± 419 m. The retreat estimation has high uncertainty due to large variability in individual retreat. Further, investigation on area loss suggests an overall loss of 12.6 ± 7.5 % for 40 years from 1960 onwards. Another key parameter to understand health of glacier is mass balance. However, mass balance data are available for few glaciers, and cumulative mass loss for last 44 years is estimated as 20 ± 6 m. The average snow cover in the Himalaya from 2000 to 2011 varied between ~0.3 and 0.03 million km². The average volume of snow is estimated at ~54.5, ~9.3 and ~14.5 billion cubic meters in the Indus, Ganga and Brahmaputra basins, respectively. These investigations have also brought out limitations of present methodology in glacial investigations, and therefore, new approach to study distribution of glacier depth, mass balance, moraine-dammed lakes and glacier dynamics is proposed.