DIVECHA CENTRE FOR CLIMATE CHANGE
INDIAN INSTITUTE OF SCIENCE, BANGALORE 560012, INDIA
A paper entitled, "The state and fate of Himalayan glaciers" published in prestigious journal of SCIENCE on April 20, 2012. This is a review article coauthored by Anil Kulkarni, Distinguished Visiting Scientist at Divecha Centre for Climate Change and it provides contemporary understanding of Himalayan glaciers and possible changes in near future.
WHY STUDY HIMALAYAN GLACIERS ?
Himalayan glaciers are a focus of public and scientific debate, as almost 800 million people live in the catchments of the Indus, Ganges and Brahmaputra, and rely to varying extents on the water released from glaciers. Therefore, numerous investigators from different parts of the world has carried out studies to understand changes in distribution of glaciers in Himalayan and Karakoram (H-K) region.
HOW MUCH WATER STORED IN HIMALAYA ?
Numerous investigations based on historical data suggest that glacial extent in H-K region is varying from 49650 to 43178 km2. Recent investigation based on satellite images suggest an area extent of 40800 km2. In the Indian H-K region the estimate is varying from 23300 to 26757 km2. In this region, volume measurements are available for few glaciers, therefore, models were applied to estimate volume of glaciers. Empirical estimates are highly uncertain and range from about 2300 km³, taking the slope-dependent ice thickness into account, to ~3600 -~6500 km³ based on volume-area scaling. The uncertainties in these estimates is very large, however, these estimates are substantially less than 13,300 km3 estimate presented in Fourth Assessment Report of the IPCC.
WHAT IS RATE OF RETREAT?
The loss in glacier area is already estimated for more than six thousand glaciers covering an aerial extent of twenty thousand sq km. These glaciers are distributed in all parts of H-K region and covers almost half of the total glaciated extent. The glaciers in H-K region are losing an average 0.4% area per year. This is general tendency and loss in area is different in different parts of H-K region. The length measurements are also available for more than 100 glaciers in H-K region. These are retreating from mid-19th century, expect 1920-1940, where half of glaciers were stationary or advancing. Some large glaciers in Karakoram are stable or advancing. However, assessment based on length measurements could be misleading, as recent investigations have shown that even if glaciers are losing same amount of mass, its retreat could be influenced by slope and length. Therefore, it would be useful to understand changes in glacial mass to assess future changes in glacial extent.
HOW MUCH LOSS IN GLACIAL MASS ?
Measurements of mass budget for glaciers in H-K region are relatively few and for short duration. The available data suggest that mass budget over large part of Himalaya has been negative over past decades and rate of loss is increased after roughly 1995. Rough estimates suggest that glaciers in Indian Himalaya losing mass at the rate of 16 Gt per year. The loss in mass for many small glaciers located in low altitude range could be larger than mean and it could be as high as 1 m per year. This is substantial loss considering mean depth of small glaciers could be between 30 and 50 m. These small glaciers and ice fields are important source of water for many mountain communities. By considering small volume and large mass loss, this source of water could be significantly influenced in near future and could affect sustainability of many mountain communities. Therefore, major program needs to be undertaken to study changes in small glaciers and its impact on local communities.
NEED TO MONITOR HIMALAYAN GLACIERS
The investigations in Indian Himalaya suggest that most of the glaciers are retreating and also loosing mass. This consistent shrinkage in mass and areal extent can affect stream runoff over a long term. In addition this process can be further influenced if more glacier lakes are formed due to increase in debris cover and if Black Carbon is transported in accumulation areas of the glaciers. Therefore, continuous monitoring is needed to understand changing dynamics of Himalayan glaciers.
For more information, visit http://www.youtube.com/watch?v=k1_5c6UzIZ0&feature=plcp ; http://www.dccc.iisc.ernet.in/
Reference: T.Bolch, A.Kulkarni, A.Kääb, C.Huggel, F.Paul, J.G.Cogley, H.Frey, J.S.Kargel, K.Fujita, M.Scheel, S.Bajracharya, M.Stoffel, The State and Fate of Himalayan Glaciers. Science 20 April 2012: Vol. 336 no. 6079 pp. 310-314, DOI: 10.1126/science.1215828