ACCUMULATION AND FLOW-RATES OF ICE ON CHHOTA SHIGRI GLACIER, CENTRAL HIMALAYA, USING RADIO ACTIVE AND STABLE ISOTOPES

Systematic isotopic studies based on natural and artificial radio-isotopes (Si-32, Cs-137), stable isotopes (delta O-18) and total beta activity measurements have been carried out on Chhota Shigri glacier, Himachal Pradesh, central Himalaya, to study the dynamics of the ice, meltwater composition and to identify the deposition of the Chernobyl fall-out in the Himalayan region. Using Si-32 concentrations, the snout ice has been dated at approximately 250 years, based on which the past average surface ice-flow rate has been estimated as approximately 28 m year-1 Based on delta O-18 variations. in a shallow ice core, thc accumulation rate of the ice has been estimated at approximately 520 kg m-2 year-1. Si-32 measurements of snout ice and englacial meltwaters indicate that at least 55% of the snow meltwater mixed with 45% of the old ice-melt water that emerged from englacial streams in the month of August 1987. Deposition of the artificial radionuclide (Cs-137) and the very high total beta activity observed in snow samples on Chhota Shigri glacier give the first evidence of Chernobyl fall-out deposition in the Indian Himalaya.