Oxygen isotopic ratios of some Himalayan glaciers

Self Cite

Systematic isotopic studies based on natural and artificial radio-isotopes (32Si, 137Cs), stable isotopes (δ18O) and total β 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 32Si concentrations, the snout ice has been dated at ~ 250 years, based on which the past average surface ice-flow rate has been estimated as ~ 28 m year−1. Based on δ18O variations, in a shallow ice core, the accumulation rate of the ice has been estimated at ~520kgm−2 year−1. 32Si 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 (137Cs) and the very high total β activity observed in snow samples on Chhota Shigri glacier give the first evidence of Chernobyl fall-out deposition in the Indian Himalaya.

Section: (B) Artificial Y-activiry Measurementssupporting

confidence: 87%

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

Nijampurkar

Rao

1992

Self Cite

“…-100/00 with a mean value of -7 ± 3%0. According to Niewodniczanski and others (1981), no systematic dependence of 8 18 0 on altitude is observed in the sampling range 4050-4750 m. Our observations are similar to those of Ambach and others (1986), Wushiki (1977) and Nijampurkar and Bhandari (1984), which also fail to indicate any altitude dependence in isotopic fractionation. As expected, values are much higher than those observed in Changme Khangfu glacier, Sikkim valley (-19 ± 2%0), as the snow samples were collected from higher altitudes (4900-5400 m).…”

Section: (B) Artificial Y-activiry Measurementssupporting

confidence: 87%

“…Using the isotopic composition of oxygen and hydrogen (8 18 0 and 8D ) as climatic indicators, much work has been done in polar and semi-polar regions, particularly in Greenland, Antarctica and the Alps (Dansgaard and others, 1969;Ambach and others, 1972;Nijampurkar and others, 1986;Jouzel and others, 1987). The few stable isotopic studies that have been reported for the temperate (Himalaya) and sub-tropical (Dunde Ice Cap) regions indicate that these measurements can also be usefully applied to the study of climatic variations in these regions (Grabczak and others, 1983;Nijampurkar and Bhandari, 1984;Thompson andothers, 1988, 1990;Wake, 1989). Here, we report the results of isotopic studies on Chhota Shigri glacier and discuss them in relation to the pertinen t glaciological parameters.…”

Section: Introductionmentioning

confidence: 86%

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

Nijampurkar

Rao

1992

Self Cite

Systematic isotopic studies based on natural and artificial radio-isotopes (32Si,137Cs), stable isotopes (δ18O) and total β 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.Using32Si concentrations, the snout ice has been dated at ~ 250 years, based on which the past average surface ice-flow rate has been estimated as ~ 28 m year−1. Based on δ18O variations, in a shallow ice core, the accumulation rate of the ice has been estimated at ~520kgm−2year−1.32Si 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 (137Cs) and the very high total β activity observed in snow samples on Chhota Shigri glacier give the first evidence of Chernobyl fall-out deposition in the Indian Himalaya.

“…18 O concentrations in snow, pits, surface ice and a shallow ice core d 18 O concentrations in snow and ice The results of the analysis of the fresh snow and surface ice samples collected at different altitudes (in both the accumulation and ablation zones of the glacier) are shown in Figure 3.The d 18 O in snow samples varied from^5% to^9%; however, there is no systematic variation of d 18 O with increasing altitude, as these samples represent only a single snowfall event and not the annual precipitation. These oxygen isotope ratios are similar to those reported in our earlier studies on Himalayan glaciers (Nijampurkar and Bhandari, 1984;Nijampurkar and Rao, 1992). The d 18 O values of surface ice samples at different altitudes range from^11% tô 13.4%.…”

supporting

confidence: 89%

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

Nijampurkar¹,

Rao²,

Sarin³

et al. 2002

Measurements of natural and artificial radioisotopes (32Si, 210Pb and 137Cs) and oxygen isotopes (δ18O) 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 δ18O 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 δ18O variation is documented for this glacier.