CHANGES IN DYNAMICS OF PENSILUNGPA GLACIER, WESTERN HIMALAYA, OVER THE PAST TWO DECADES

摘要

The health of Himalayan glaciers has been a cause of prime concern for the scientific community as well as policy makers. The state of glacier dynamics is considered a significant indicator of glacier health. Surface ice velocity (SIV) is one of the important parameters which determines the glacier dynamics. The SIV is driven by several factors which include changes in hypsometry and slope, mass load, orientation of the glacier, basal sliding, debris cover and the variation in meteorological parameters. Further, as remote and inaccessible location of mountain glaciers inhibits their field based monitoring, remote sensing with repeat and synoptic coverage offers the best alternative. In present study, we have used multi-temporal satellite images from Landsat Thematic Mapper (TM). Enhance Thematic Mapper (ETM+) and Operational Land Imager (OLI) sensors for past two decades (1993/94 - 2016/17) to ascertain the variations in the SIV of the Pensilungpa glacier, Suru sub-basin, western Himalaya. For estimation of glacier velocity, the standard procedures using image to image cross-correlation technique have been employed. Results reveal that the mean glacier wide SIVs in the accumulation zone (ACZ) of the glacier have been decreasing, those in the upper ablation zone (ABZ) have been stable and even increasing, while the lower ABZ exhibits a slowdown. This slowdown may be linked with consistent increase (~ 40% in past 23 years) in the supraglacial debris cover extents on the glacier. The spatio-temporal pattern of fluctuations in the SIV of the glacier seem to be controlled primarily by variations in the regional meteorology, glacier mass balance and debris cover extent.