Radiometric age of the snout ice of Nehnar glacier

Abstract

The surface ice taken from the snout of the Nehnar glacier (Kashmir) in western Himalaya has been dated using radioisotopes ³²Si and ²¹⁰Pb to be 500 years. Based on the age distribution of ice and the expected activity of ³²Si in the fallout, the average rate of glacier movement over a period of the last few centuries is estimated to be about 6 m/yr. The data obtained on ³²Si and ²¹⁰Pb activities in the surface ice samples in the ablation zone support our previous observation about the existence of five zones of alternately high and low activity of ²¹⁰Pb, which probably is a consequence of complex dynamics of Nehnar glacier. The vertical profile of ²¹⁰Pb activity in an ice core correlates directly with the total beta activity. This radioactive horizon at an altitude of 4140 m appears to be located at a depth of 10-12m, which is lower compared to the 2-3 m observed earlier at an altitude of 4150 m.