Isotopic study on Dokriani Bamak glacier, Central Himalaya: implications for climatic changes and ice dynamics

Abstract

Measurements of natural and artificial radioisotopes (³²Si,²¹⁰Pb and ¹³⁷Cs) and oxygen isotopes (δ ¹⁸O) have been carried out on surface snow and ice, shallow snow pits and an ice core collected from Dokriani Bamak glacier, central Himalaya, to study the dynamics of glacier ice and short-term climatic changes. Based on the ³²Si and ²¹⁰Pb activities in the meltwaters, the age of the snout ice is 400 years and the flow rate of ice along the glacier length is ~ 14 m a ^-1. The specific activity of ¹³⁷Cs, corresponding to 1963 fallout, in the surface ice at the equilibrium line yields a flow rate of 32 m a ^-1, a factor of two higher than that derived for the snout ice. The depth variation of ¹³⁷Cs concentration in a shallow ice core yields a mean accumulation rate of 0.43 m a ^-1 for the glacier ice over the past decade. The δ ¹⁸O of snout ice (-13.4%.) is significantly depleted compared to the average value of -9.2%. in the shallow ice core, indicating that cooler climatic conditions prevailed around AD 1600. Based on the oxygen isotopic ratios in the shallow pits, an "altitude effect of 0.9%. per 100 m in δ ¹⁸O variation is documented for this glacier.