Estimation of aerial and volumetric changes of selected glaciers in Jammu & Kashmir

Abstract

Himalayan glaciers numbered around 9575 influence the hydrology of the headwater regions of the river Indus, the Ganges and the Brahmaputra. These glaciers are under the overall recessional regime since 1850’s with intermittent phases of glacier advancements. Glaciers are the most illustrative examples of climatic variations as their advance and retreat are linked with the cold and warm periods. Response of the glaciers characterizes the long-term changes in the climate and hydrology of a region and provides valuable insight on the water resources management challenges in a region. Glaciers play a very important role in the mountain hydrological systems by influencing quantity and quality of headwater river flows and also by influencing the local and regional climate through a feedback mechanism. The state of Jammu & Kashmir have around 5400 glaciers covering and area of 29213 km2.This constitute around 56% of glaciers in the Indian Himalayas and about 78% glacier cover area of the Indian Himalaya. However large part of these glaciers is in the Karakoram mountains and Shyok basin alone holds 2454 glaciers which cover 10810 km2 area. Nubra, Gilgit, Kishenganga, Upper Indus basin including Indus, Suru and Zanskar basins are the glacier bearing basins in the Ladakh region. These glaciers distributed along three major mountain ranges, Karakkoram range, Ladakh mountain range and Zanskar rage and cover two distinct glacio-hydrological regimes. Ladakh mountain range is in the Cold-arid regime and rest of the area experience winter snow dominant Alpine glacio-hydrologic regime. Glaciers in the Kashmir and Jammu province are spread over the Great Himalayan mountain range and Pir Panjal range and under the Alpine glaciohydrological regime. Sind, Liddar and part of the Chenab basins are the major glacier bearing basin in these region. There are 57 glaciers are in the Sind basin covering an area of 39.94 km2. However 44 of them are small glaciers with less than 1 km2 area. 48 glaciers are part of the Liddar basin covering an area of 38.95 km2 and 41 of them have an area less than 1 km2. In the present study ten glaciers in the Ladakh Mountain range under the cold-arid glacio-hydrologic regime and two glaciers in the Zanskar range and seven glaciers in the Drass and Kashmir region of great Himalayan mountain range under the Alpine glacio-hydrolgical regime have been investigated. Change in the glacier length and area during the last three decades (27-34 years) have been investigated by topographic method by using Survey of toposheet and latest high resolution remote sensing imageries combined with extensive field survey of these glaciers. Volume change is calculated by using glacier area- volume scaling relationship, calibrated for the Himalayan region. Specific mean mass balance of individual glaciers were deduced from cumulative volume change of the glaciers. Most of the glaciers were visited during the two expeditions in 2007 and 2008. Ladakh mountain range and Kashmir region harness glaciers in distinct elevation bands of the Himalayas. In the Ladakh range the lower extent of the glacier generally is around 5200 m a.s.l. ,whereas glaciers in the Kashmir region of the great Himalayan range are situated at much lower altitude with glacier snout reaching up to 3600 m a.s.l. The results of the present study suggest there is no ‘altitude effect’ on the glacier change in these two regions. The changes experienced by the glaciers of higher altitudes at 5200 m a.s.l and above is changing at a similar rate that of glaciers at 3600m a.s.l. and above. This result is strongly support the global analyses which showed major glacier systems of the world in different altitudes and latitudes are responding in a similar way. Change in the area covered by the glacier is an important parameter of the glacier change studies. Apart from giving a measure of glacier change, much detailed than the information of glacier recession data, the change in the glacier cover influence the energy exchange in the high altitude region. Lesser glacier cover imply, lesser area of the mountain having higher albedo which result into progressively higher radiation absorbed by the mountain slopes warming up the higher altitude glacier regions. Ladakh mountain range is characterised by small glaciers and the area of glaciers evaluated in the present study range from 0.022 – 1.164 km2. The area of glaciers selected for the study in the Kashmir region ranged between 0.539 to 7.47 km2. The percentage area change during the past 34 years in the Ladakh range vary from 6.5 to 100%. If we exclude the highly degrading smaller glaciers of Khardug La , the upper range of aerial change is 18.6%. In the Drass and Kashmir regions of the great Himalayan range, change in the glacier ranged between 2.9 to 34.5%. Changes of glaciers are often debated in our country in terms of recession rate of glacier frontal margins. However, absolute values of rate of glacier recession can not be compared with other glaciers as length of each glacier varies considerably. The recession rate of small glaciers in the Ladakh range is in the order of 0 to 4.5 m/yr, whereas for longer glaciers in the Kashmir region, recession rate is as high as 20 m/yr. It is observed that absolute value of glacier recession and glacier volume change for selected glaciers in different mountain ranges show no relationship between these two parameters. To compare the length change of different glaciers, normalized glacier length has been used. The similarity between the normalized length change of glaciers in the two characteristically different glacier systems are striking. The length change of these glaciers, small glaciers of Ladakh range and bigger glaciers of Great Himalayan range of Kashmir range between 0 to - 0.17. This observation suggests that the glaciers in the cold-arid system as well as in the Alpine glacio-hydrological regimes are may be changing at a comparable rate. Absolute values of glacier volume change show the characteristics of to distinct glacier regimes. Small glaciers of the Ladakh range have small melt component ranging from 0.13 x 106 m3 to 7.16 x 106 m3 of cumulative ice loss during 34 years study period. Glaciers in the Kashmir region showed higher range of melt out component ranging from 2.73 x 106 m3 to 72.93 x 106 m3, primarily reflecting the wide range of glacier size existing in the region. In percentage terms volume change of glaciers studied in the Ladakh region range between 8.7 to 100%. In the Kashmir region, the volume change of glaciers range between 4- 43.7 % during 27 to 34 year study period. Relationship between glacier volume change to the normalised glacier length change also investigated. The relationships between these two variables are better in the Ladakh range as compared to the glaciers studied in the Kashmir region. Glaciers in the Ladakh range are characteristically similar as most of them are small cirque glaciers with a much simpler flow regime as compared to the glaciers studied in the great Himalayan region. This suggests that the valid relationship between glacier length changes to the volume change could be explored for the glaciers belonging to same classes. Sample size of the present study is too little for better evaluation of this aspect. Global analyses of glacier change with mass balance data of 30 reference glaciers with continuous measurements since 1976 show increased average annual mass loss through last three decades. Average annual mass loss for the period 1976-85 was 0.14 m w.e. which increased to 0.25m w.e. during 1986-95, which doubled to 0.58 m w.e. during 1996-2005 period. This analysis was based on the data available with World Glacier Monitoring Services (WGMS). Calculation of mean annual ice loss from 1946 to 2006 by different methods concluded that the average annual mass loss of glaciers is 0.35 m w.e. These global estimates suggested that the glacier mass balance has became more negative since 1970’s. In the present study we found that the mass loss of glaciers, derived by the topographic method is comparable with the average mass balance of glaciers assessed by the direct glaciological method during different periods of the last two and a half decades in the Himalaya. Average specific mass balance calculated by the glaciological method ranged between -0.98 to -0.26 m w.e. yr-1. Compared to this, the average specific mass balance derived from present study range from -0.50 m w.e. yr-1 for Galdar glacier to -0.04 m w.e. yr-1 for Nagche glacier. Evaluation of annual net balances of these glaciers in terms of percentage annual degradation with respect to the total glacier storage range between 0.15 to 1.62% and results suggests that the small glaciers are degrading at faster rate. Glacier Lake Outburst Floods (GLOF) are another manifestation of glacier shrinkage in a region. During the course of the expedition in the Ladakh range, the NIH team has got a rare opportunity to study a GLOF near the Pangong Lake on 15 September 2007. A bridge across the stream on the main Tangse- Pangong road was washed off during the flood and the road got damaged at couple of other places. The evacuation of the flood water at lower reaches continued for about 14 hours and an estimated 0.8 to 1 million cubic meters of water was evacuated by this GLOF.