Chemical composition and isotopic signatures of ice and snow over a Himalayan Glacier (Satopanth) in India
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This study reports the chemical composition and isotopic signatures of snow and ice over a Himalayan Glacier in India. An observational campaign was carried out from September 22, 2016, to October 2, 2016, over Satopanth in central Himalaya. The pH value of ice and snow, respectively, was 5.6 ± 0.4 and 5.9 ± 0.35 over the glacier, indicating moderate acidity of the glacier components. Calcium (Ca2+) was the dominant component in snow (35.2%), while sulfate (SO42−) was dominant in ice samples (52.7%). The neutralization factor was estimated to find the extent of neutralization of acidic fractions by basic components. It is found that Ca2+ was the prominent neutralizing factor both in snow and ice over the region. Oxygen and hydrogen isotopic analyses of snow, surface layer ice and debris-covered ice suggest that the moisture source is common for all three components. δD and d-excess values of snow at Satopanth are different than that of those for Chorabari, Dokriani and Tiprabank Glacier, indicating the plausibility of different sources of moisture for these glaciers. Limited observations suggest that the interaction of ice with the debris has no impact on the isotopic signatures of the ice over the region; such non-alteration of isotopic signatures makes the region important for ice core-based paleoclimatic studies.
KeywordsHimalayan Glacier Chemical composition Snow and ice Isotopic analysis
The melting and retreat of glaciers due to global warming have been a major issue in the Himalayan region. Even though major portion of the glaciers in Himalaya are retreating, some portion are remaining stationary or advancing [3, 27, 39]. The dust particles present over glaciers have significant effect in controlling the glacier retreat. It is shown that the high loading of dust works as an insulator and moderates solar heating of the underlying surface . The chemical composition of snow and ice over glaciers indicates the essential minerals and salts present in the glacier, which can account for the climatic and environmental changes . The ionic deposition over glaciers are mainly contributed by circulation patterns and activities in the local environments . Many glaciers in central Himalaya are featured with the covering of soil and stone debris over the ice surface. The climate responses of debris-covered glaciers are poorly understood . It is suggested that debris-covered glaciers can withstand glacier retreat by 45–50% more as compared to the bare glaciers . Since the last century, a number of attempts have been made by several investigators to study the various glaciological aspects of the Himalayan Glaciers (e.g., [6, 12, 17, 20, 23, 27, 28, 29], etc). However studies on ionic composition of snow/ice observations are limited, as most of the studies are oriented in the geological perspective over central Himalaya. Hence a campaign mode study was conducted over debris-covered Satopanth Glacier during September 22, 2016, to October 2, 2016, in central Himalaya to cover the chemical aspects. The exploration was mainly focused on the measurements of aerosols and chemical composition of ice and snow over the glaciers. Isotopic analysis also has been carried out with the collected samples of ice and snow over the region. Stable isotopes of water are widely used in understanding the hydrological and paleoclimatic features (e.g., [36, 37]). Stable isotopic composition of ice/snow mainly depends on precipitation isotopic composition and gets modified with the base temperature of glacier. Further melting, percolation, snow drifting, evaporation and sublimation also alter the isotopic composition of ice. Despite such complications, δD and δ18O contents of ice represent the climatic history of the region . In the Indian Himalayan region, no altitude effect was observed in δ18O of fresh snow collected from Changme-Khangpu, Nehnar, Chhota Shigri Glaciers [30, 31, 33]. It is reported that the glacial melt contribution from Gangotri Glacier at Devprayag is 11% . The recent isotopic studies, reported dominance of westerly and monsoon sources during winter and summer, respectively, in the Chorabari and Dokriani Glaciers [21, 43]. Still, stable isotopic studies for the Himalayan Glaciers are limited [13, 31, 32, 34, 42]. This paper exclusively presents the chemical composition of snow and ice and its isotopic signatures over Satopanth Glacier. The sample collection and data are explained in Sect. 2. Results in detail are discussed in Sect. 3 and summary is provided in Sect. 4.
2 Sample collection and data
Oxygen and hydrogen isotopic analyses of the snow and ice samples were carried out using a LGR isotopic water analyzer (Model: TIWA-45-EP; ). These analyses yielded simultaneous δD and δ18O isotopic data through high-resolution laser spectroscopy that quantifies concentrations of individual isotopologues of H2O and calculates isotopic ratios [16, 25]. Using the LASER absorption property, the stable isotope ratios are measured directly based on the molecular mass dependency of the individual absorption lines. The autosampler is used to inject water sample from the sample vial using 1.2 µL syringe to an injector block (vaporization chamber) heated at 70 °C which is connected to the analyzer. A Teflon tube is connected to the pre-evacuated (using pump) optical cavity. For each sample and calibrated standard, nine injections are measured and average values are reported. The precision of the hydrogen and oxygen isotopic measurements was better than 1.0‰ and 0.1‰, respectively. Accuracy of the analyses was monitored through isotopic measurement of International (USGS-46 and USGS-47) and our in-house lab standard (IITM-A) standards. The conventional δ notations are presented with reference to V-SMOW (Vienna standard ocean water), in this study, the d-excess values for the samples are estimated as (δD-8 × δ18O) .
3 Results and discussion
3.1 Chemical composition of snow and ice
3.2 Neutralization factors
Neutralization factors of different components in snow and ice samples
3.3 Isotopic analysis
Sample details and their δD and δ18O values with d-excess
− 92.4 ± 0.16
− 14.1 ± 0.05
− 94.2 ± 0.09
− 14.5 ± 0.03
− 86.1 ± 0.11
− 13.3 ± 0.09
4 Summary and conclusion
A campaign was carried out over Satopanth Glacier in Himalaya during September 22–October 3, 2016, periods to collect snow/ice samples for its chemical characterization and also to analyze its isotopic signatures. The pH of glacier ice was found to be 5.6 ± 0.4, and deposited snow was found to be 5.9 ± 0.35 over Satopanth Glacier. This indicates toward more acidity in ice. The SO42− was the major contributor to ice (52.7%), whereas Ca2+ dominated in snow (35.2%) over Satopanth Glacier. Debris cover over glacier could be major source of calcium than long range transport of the minerals. Estimates of neutralization factors revealed that Ca2+ component is able to neutralize and keep the acidity of ice and snow under check over the region. Oxygen and hydrogen isotopic analyses of snow, surface layer ice and debris-covered ice suggest that the moisture source is common for all three components in the glacier. It is also identified that the interaction of ice with the debris has no impact on the isotopic signatures of the ice. δD and d-excess values of snow at Satopanth are different than that of those for Chorabari, Dokriani Glaciers and Tiprabank Glacier, which indicates the plausibility of different sources of moisture for these glaciers.
The observations over Satopanth Glacier suggest that the snow samples present over the glacier are less acidic compared to ice plausibly due to more neutralization of acidic fraction by dominance of Ca2+ in snow. Limited observations over the glacier suggest that the interaction of ice with the debris has no impact on the isotopic signatures of the ice over the region such non-alteration of isotopic signatures makes the region important for ice core-based paleoclimatic studies. Hence, more exploration is necessary in Satopanth Glacier to unravel its changes in chemical and paleoclimatic aspects in the context of climate change.
Authors acknowledge Director IITM and Vice chancellor HNBGU for their constant encouragements. IITM is funded by MoES, Govt. of India, New Delhi. Author A.S.Gautam thanks SERB-DST Project for financial support (No. SB/EMEQ-043/2014 dated March 08, 2016). Authors A. S. Panicker and A. S .Gautam acknowledge for the Junior associateship program of the Abdus Salam International centre for theoretical Physics (ICTP), Italy.
Compliance with ethical standards
Conflict of Interest
On behalf of all authors, the corresponding author states that there is no conflict of interest.
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