Temporal Variation in the Major Ion Chemistry of Chhota Shigri Glacier Meltwater, Lahaul-Spiti Valley, Himachal Pradesh, India

Glaciers, while commonly regarded as sensitive indicators of climate change, can also be affected by various factors like atmospheric deposition. Study of major ions (Mg2+, Ca2+, Na+, K+, HCO3 (-), SO4 (2-) and Cl-) of meltwater draining from Chhota Shigri glacier was carried out to understand weathering and geochemical processes controlling the major ion chemistry of the glacier meltwater. Chhota Shigri glacier meltwater was sampled in August 2008. Mg2+ is the dominant cation followed by Ca2+, K+ and Na+. Whereas HCO3 (-) is the dominant anion followed by SO4 (2-) and Cl-. The high ratio of Ca + Mg/TZ(+) i.e. 0.77 and low ratio of Na + K/TZ(+) i.e. 0.23 shows that carbonate weathering is the dominant mechanism controlling major ion chemistry followed by silicate weathering in the study area. In this paper we aim to evaluate the possible effect of various processes that affect the chemistry of meltwater of Chhota Shigri glacier. Decadal variation in the major ion chemistry of Chhota Shigri glacier meltwater was carried out by comparing the hydrochemistry of August 2008 with previous study carried out in 1987. Comparison between the two data sets shows that cations like Ca2+ increased nearly 6 times, Mg2+ 87 times, Na+ 10 times and K+ 19 times, while anions like Cl- increased nearly 12 times, HCO3 (-) 85 times and SO4 (2-) 49 times between 1987 and 2008. This could be attributed to increased weathering rates due to climate warming, atmospheric deposition or a combination of both. Annual specific mass balance of Chhota Shigri glacier was often sharply negative during 2002-2010, pointing to glacier recession, which may be also attributed to global climatic change.