Basal flow rate of Changme-Khangpu glacier, Sikkim Himalaya based on32Si and210Pb chronology

Abstract

Using environmental radioisotopes silicon-32 and lead-210, the radiometric ages of ice at the surface and at 5 m depth at the snout of the Changme-Khangpu (CK) glacier have been calculated to be 100 and > 650 years respectively. Based on i) these age estimates, ii) a net uniform accumulation rate of 0.7 m/yr of ice in the accumulation zone; and iii) applying a simple ice flow model assuming melting of ice of 1 cm/yr at the base of the glacier, it is demonstrated that the average basal flow rate of the CK glacier is much smaller (at least by a factor of three) than that of 40 m/yr estimated for the surface ice. This observation is in good agreement with the earlier work on basal flow rates and indicates that the deeper ice near the bed rock travels much slower than the surface ice.

The influence of debris cover and glacial lakes on the recession of glaciers in Sikkim Himalaya, India

“…and was first mapped during an expedition of German researchers (Finsterwalder, 1935). Changme Khangpu, one of the Sikkim glaciers, has been studied using Si-32 and Pb-210 chronology, and the results showed (1) a retreat rate of 6 m a -1 between 1976 and 1981, (2) an accumulation rate of 0.7 m a -1 , and (3) a basal flow of 0.01 m a -1 compared to a surface flow of 40 m a -1 , indicating that the deeper ice near the bedrock travels much more slowly than the surface ice (Shukla and others, 1983;Nijampurkar, 1985;Nijampurkar and others, 1985). Another study estimated the average rate of glacier retreat as 13 m a -1 , for 26 glaciers in Sikkim, using satellite images between 1976 and 2005 (Raina, 2009).…”

Accumulation and flow rates of ice on Chhota Shigri glacier, central Himalaya, using radio-active and stable isotopes

“…Earlier, long-lived radioisotopes, such as 32 Si with a half-life of ∼ 140 years (Somayajulu and others, 1987; Hofmann and others, in press) and 210 Pb (half-life = 22.3 year) have been used to estimate the ages of young and old ice of several Himalayan glaciers, using the standard radioactivity decay equation and a simple two-component flow model. These data, in turn, have been used for estimating surface and basal flow rates of the glacier ice (Nijampurkar and others, 1982; Nijampurkar, 1985). The artificial radionuclide 137 Cs and total β activities, produced during atmospheric nuclear testing (1950–80) and during nuclear-reactor accidents such as Chernobyl in April 1986, can be used as time-markers to estimate accumulation rates of ice in glaciers (Shukla and others, 1983; Von Gunten and others, 1983; Pourchet and others, 1988).…”