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 (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.

Study of isotopic seasonality to assess the water source of proglacial stream in Chhota Shigri Glaciated Basin, Western Himalaya

“…The glacier melt components (snow and glacier ice) obtained from winter deposited snowpack and shallow ice core (on the basis of their active melt layers involved in runoff generation) showed distinct isotopic characteristics. Isotopic composition of snow (δ 18 O/δD: −8.83‰/−34.13‰) and glacier ice (δ 18 O/δD: −13.37‰/−86.01‰) in Chhota Shigri glacierized catchment is observed to be nearly unvarying with isotopic qualities of snow and ice in previous studies on Chhota Shigri glacier, Dokriani glacier (Nijampurkar et al, ; Nijampurkar and Rao, ), and Gangotri glacier catchments (Lambs, ; Table ).…”

“…values are evident of being progressive depletion (Figure 3). Rainwater over Chhota Shigri glacier catchment shows analogous and consistent pattern of isotopic seasonality with Chorabari glacier , Dokriani glacier (Verma et al, 2018), and Gangotri glacier catchments (Rai et al, 2009) (Nijampurkar et al, 2002;Nijampurkar and Rao, 1993), and Gangotri glacier catchments (Lambs, 2000; Table 3). Trend of isotopic shift in Chhota Shigri stream remained consistent and in accordance with the observed monthly variation in Chorabari glacier stream (Table 1a and Figure 5b; and Gangotri glacier stream in UGB (Rai et al, 2009).…”

Role of glaciers in watershed hydrology: a preliminary study of a "Himalayan catchment"

“…This glacier has receded 726 m in 43 years with an average rate of 16.8 m/yr and has lost approximately 22% of its volume from the total storage of 385×10 6 m 3 (Dobhal et al, 2004). The average accumulation rate of this glacier is 0.43 my −1 (Dobhal et al, 2007;Nijampurkar et al, 2002), with an average accumulation area ratio (AAR) of 0.66. Another small glacier with an area of 0.46 km 2 is also part of the Din Gad catchment, and its pro-glacial stream joins Din Gad at 3400 m a.s.l.…”

“…Therefore, a glacier's role in influencing the flow regimes of mountain rivers across the Himalayan arc would vary considerably. The Dokriani glacier in the Ganga basin is one of the most studied glaciers in the Indian Himalaya and various facets of glacio-hydrological processes have been investigated earlier (Singh et al, 1995;Hasnain and Thayyen, 1999a, b;Hasnain, 1999;Thayyen et al,1999Thayyen et al, , 2003Thayyen et al, , 2005aThayyen et al, , b, 2009Singh et al, 2000aSingh et al, , b, 2003aNijampurkar et al, 2002;Dobhal et al, 2004Dobhal et al, , 2008. In this work, an attempt has been made to highlight the fundamental differences between Alpine and Himalayan glacier hydrological systems and the role of glaciers in influencing runoff characteristics of monsoon dominated "Himalayan catchments".…”

Role of glaciers in watershed hydrology: ''Himalayan catchment'' perspective

“…This glacier has receded 726 m in forty three years with an average rate of 16.8 m/yr and has lost approximately 22% of its volume from the total storage of 385×10 6 m 3 (Dobhal et al, 2004). Average accumulation rate of this glaciers is 0.43 my −1 (Dobhal et al, 2007;Nijampurkar et al, 2002) with an average accumulation area ratio (AAR) of 0.66. Another small glacier with an area of 0.46 km 2 is also part of the Din Gad catchment and its pro-glacial stream joins Din Gad at 3400 m a.s.l.…”