Assessment of Regional Climatic and Hydrological Changes in the Eastern Himalayan Region

Abstract:

Understanding the changes in Himalayan glaciers is of importance for assessment of the future water availability and detection of anthropogenic greenhouse effect related trends. Terrain of eastern Himalayan glaciers is harder in comparison to western and central Himalayas. For this reason long term field based measurements are not available for the glaciers of this region. Hence a glacier from Sikkim has been studied using off-field methods. Volume, area, mass balance, glacial melt and runoff for the East Rathong glacier have been estimated for the time period 1963-2011. It has been observed that the glacier is summer-accumulation type. Time series analysis has been done for the annual mass balance. Annual mass balance of the glacier is showing statistically significant negative trend and shift. Cumulative net mass balance suggests that the glacier has lost ~11 m. w. e. during last 48 years. Runoff from the glacier has increased by ~30% in the present decade in comparison to the runoff observed in 1960s. The glacier has lost ~20% of its volume from 1962 to 2013. MERRA (Modern Era Retrospective-Analysis for Research and Applications) temperature satellite data, MODIS Terra Aerosol Optical Depth (AOD) data and water balance data from Hydrological information system for Sikkim region were analyzed. The temperature of Sikkim at an altitude of 5 kms has increased by 0.7 K during 1979-2011, AOD has shown a % change over mean of +14.42% during 2001–2012, and water yield of the region has shown a % change over mean of -46.77% during 1971-2005. The results suggest that it is important to understand aerosols-cloud interaction and their impact on precipitation and glacier-melt patterns over Himalayan region, regions dependent for their water needs on eastern Himalayan glaciers will soon have to adapt to use of scarce water resources, river flow reduction would come sooner as glacier area and volume are reduced more rapidly due to increasing air pollution, better predictive tools for factors affecting glacier melt rates are urgently needed for planning for climate change adaptation.

The presentation will link the changing regional climate of Sikkim to the changing area and volume of the glaciers and the hydrology of the region. The results of our work can be used by hydrological modelers to predict the future water availability of the region.