Glacier Ice Core Research Articles

Glacial secrets uncovered: Revealing the modes of survival of metabolically active microbial communities entrapped in polar glacial ice

Glacial secrets uncovered: Revealing the modes of survival of metabolically active microbial communities entrapped in polar glacial ice

An extraction method for nitrogen isotope measurement of ammonium in a low-concentration environment

Abstract. Ammonia (NH3) participates in the nucleation and growth of aerosols and thus plays a major role in atmospheric transparency, pollution, health, and climate-related issues. Understanding its emission sources through nitrogen stable isotopes is therefore a major focus of current work to mitigate the adverse effects of aerosol formation. Since ice cores can preserve the past chemical composition of the atmosphere for centuries, they are a top tool of choice for understanding past NH3 emissions through ammonium (NH4+), the form of NH3 archived in ice. However, the remote or high-altitude sites where glaciers and ice sheets are typically localized have relatively low fluxes of atmospheric NH4+ deposition, which makes ice core samples very sensitive to laboratory NH3 contamination. As a result, accurate techniques for identifying and tracking NH3 emissions through concentration and isotopic measurements are highly sought to constrain uncertainties in NH3 emission inventories and atmospheric reactivity unknowns. Here, we describe a solid-phase extraction method for NH4+ samples of low concentration that limits external contamination and produces precise isotopic results. By limiting NH3atm exposure with a scavenging fume hood and concentrating the targeted NH4+ through ion exchange resin, we successfully achieve isotopic analysis of 50 nmol NH4+ samples with a 0.6 ‰ standard deviation. This extraction method is applied to an alpine glacier ice core from Col du Dôme, Mont Blanc, where we successfully demonstrate the analytical approach through the analysis of two replicate 8 m water equivalent ice cores representing 4 years of accumulation with a reproducibility of ±2.1 ‰. Applying this methodology to other ice cores in alpine and polar environments will open new opportunities for understanding past changes in NH3 emissions and atmospheric chemistry.

A multi-millennial record of rock glacier ice chemistry (Lazaun, Italy)

Active rock glaciers—known as mixtures of unconsolidated debris with interstitial ice, ice lenses or a core of massive ice—are widespread indicators of mountain permafrost. The age of a frozen rock glacier core in the Central European Alps (Lazaun, Italy) was dated to about 10,000 years. Here we report on the chemical composition of the frozen Lazaun core. The ice containing part of the core extended from about 2.8 m down to 24 m depth and consisted of two lobes—both a mix of ice and debris, separated by more than 3 m thick almost ice-free layer. The two lobes of the core showed layers of high solute content and peak values of electrical conductivity exceeding 1,000 μS/cm, but they differed in acidity and metal concentration. High acidity (minimum pH of 4.15) and high levels of elements like nickel, cobalt, zinc, manganese, iron and aluminum characterized the upper lobe, while neutral to alkaline pH and low metal values prevailed in the bottom lobe. We attributed solutes accumulated in the ice matrix to the weathering of bedrock minerals, with peak values favored by the oxidation of pyrite, or by an enhanced reactive surface area in fine-grained sediment layers. The chemical composition of the ice core also revealed signals of prehistoric atmospheric deposition from different sources including wood combustion, metal ore mining, and large volcanic eruptions (Thera, Aniakchak II). To our knowledge, this is the first study that presents the chemical stratigraphy of an entire rock glacier ice core.

The glacier–rock glacier mountain landsystem: an example from North Iceland

ABSTRACT A valley floor rock glacier in Nautárdalur, eastern Tröllaskagi, northern Iceland, has been investigated since the 1970s. Adjacent valleys are also examined as mountain landsystems. The methodology identifies ‘landform elements’ (features evident on slopes) on transects that can be identified and mapped from Google Earth imagery. Transects can be compared to show similarities and differences between slopes and valleys and can be used to trace debris and ice/snow flow paths within landsystems. The paper confirms that a glacier ice core is present throughout the Nautárdalur rock glacier. Traces of glacier activity can be found in some neighbouring small valleys but where rock glaciers are not present. Previous field observations, when coupled to current Google Earth imagery, indicate glacier ice formation and deformation over the past 200 years. The quantities and timing of weathered debris from headwall cliffs were sufficient to partly cover small glaciers, thus forming rock glaciers in some, but not all, valleys. The landsystem and transect approach thus indicate glacier origins for the rock glaciers identified. No evidence for ‘permafrost creep’ in scree slopes that might produce valley-side rock glaciers has been found.

Historic Atmospheric Organochlorine Pesticide and Halogenated Industrial Compound Inputs to Glacier Ice Cores in Antarctica and the Arctic

Ice cores collected from polar ice sheets at Site M, Dronning Maud Land, East Antarctica (Lat 75.00 S, Long 15.00 E), and Holtedahlfonna, Svalbard (Lat 79.13 N, Long 13.27 E), were analyzed for a net deposition of 25 organochlorine pesticides (OCPs) and 16 organohalogen (chlorine/bromine) industrial compounds (OHICs). Long-range atmospheric transport (LRAT) delivers contaminants to both sites, but the processes are different: Site M is affected by subsidence of air from the stratosphere to the Antarctic Plateau, while Holtedahlfonna is affected by air moving through the free troposphere. The sample from Site M is a composite core covering 1958–2000, while the Holtedahlfonna sample includes a historic record from 1953 to 2005 in six discrete samples. The five highest OCPs at Site M were chlorpyrifos, trans-chlordane, 4,4′-dichlorodiphenyl trichloroethane (DDT), ß-hexachlorocyclohexane (HCH), and dieldrin, while at Holtedahlfonna, they were chlorpyrifos, γ-HCH, α-HCH, ß-HCH, and dieldrin. The five most abundant OHICs at Site M were three dichlorobenzenes (diCBs), 1,3-diCB, 1,4-diCB, 1,2-diCB, and 1,3,5-trichlorobenzene and 1,2,4,5-tetrachlorobenzene (tetraCB) and at Holtedahlfonna, they were the same three diCB, pentachloroanisole (PCA), and 1,2,4,5-tetraCB. Of the OHICs, only hexachlorobutadiene, PCA, and hexachlorobenzene were found in all six Holtedahlfonna ice-core segments. Principal component analysis of the OCP percent of total flux values shows no similar variance among the Holtedahlfonna core segments, the whole-core value, or Site M. The principal component analysis of OHIC shows no consistent variance among any of the samples except for two Holtedahlfonna segments with the lowest OHIC values in the core.

Holocene lake-level fluctuations of Selin Co on the central Tibetan plateau: Regulated by monsoonal precipitation or meltwater?

Over the Tibetan Plateau (TP), lakes as paleoenvironmental archives have been the most extensively investigated for their sensitivities to climate change on different timescales. Well-preserved shoreline and terrace remains surrounding these lakes provide critical geomorphological and sedimentary evidence that can be used to infer past lake levels over geological timescales. These features can offer an analogue for understanding how future lake-levels respond to global warming. In this study, we investigated a series of water level-related depositional profiles around the Selin Co basin from the central TP, by dating 28 samples using K-feldspar luminescence techniques. Combining the obtained chronological data with sedimentological, stratigraphic evidence and differential GPS survey observations, the Holocene history of lake-level fluctuations in Selin Co was inferred. The results show a stable highstand between 10 ka and 7 ka but a striking subsequent lake-level decline. This pattern appears to follow the solar insolation-forced changes in the intensity of the Indian summer monsoon (ISM), particularly during the early Holocene. However, such gradual weakening of ISM intensity after the early Holocene may not interpret the dramatically rapid shrinking of Selin Co, implying other components are largely underrecognized driving factors accounting for the effective moisture of lakes in the early Holocene. Here, we argue that the increased meltwater input from glaciers and permafrost, together with increased precipitation, might have resulted in the high lake level at 10–7 ka, as the high summer temperature during the early Holocene induced massive melting water flow into the lake. By 7 ka, the abrupt lake-level drop is likely related to the decreased meltwater owing to decreasing regional temperatures documented from glacier landforms, ice cores and lacustrine sediments. Therefore, we highlight that meltwater from glaciers and permafrost poured into lakes on the central TP, particularly during warm periods on the millennial timescales, might also dominate the Holocene high lake levels.

Drought-induced biomass burning as a source of black carbon to the central Himalaya since 1781 CE as reconstructed from the Dasuopu ice core

Abstract. Himalayan glaciers are melting due to atmospheric warming, with the potential to limit access to water for more than 25 % of the global population that resides in these glacier meltwater catchments. Black carbon has been implicated as a factor that is contributing to Himalayan glacier melt, but its sources and mechanisms of delivery to the Himalayas remain controversial. Here, we provide a 211-year ice core record spanning 1781–1992 CE for refractory black carbon (rBC) deposition from the Dasuopu glacier ice core that has to date provided the highest-elevation ice core record (7200 m). We report an average rBC concentration of 1.5 µg L−1 (SD=5.0, n=1628) over the 211-year period. An increase in the frequency and magnitude of rBC deposition occurs after 1877 CE, accompanied by decreased snow accumulation associated with a shift in the North Atlantic Oscillation Index to a positive phase. Typically, rBC is deposited onto Dasuopu glacier during the non-monsoon season, and short-lived increases in rBC concentration are associated with periods of drought within neighboring regions in northwestern India, Afghanistan, and Pakistan. Using a combination of spectral and back-trajectory analyses, as well as a comparison with a concurrent analysis of trace metals at equivalent depths in the same ice core, we show that biomass burning resulting from dry conditions is a source of rBC to the central Himalaya and is responsible for deposition that is up to 60 times higher than the average rBC concentration over the time period analyzed. We suggest that biomass burning is a significant source of rBC to the central Himalaya and that the rBC record can be used to identify periods of drought in nearby regions that are upwind of Dasuopu glacier.

Developing an analytical method for free amino acids in atmospheric precipitation using gas chromatography coupled with mass spectrometry

Amino acids in rain samples offer important information on their origin and roles in biogeochemical cycling. This paper describes the development and validation of an alternative analytical procedure for amino acids in atmospheric precipitation using gas chromatography coupled with mass spectrometry (GC–MS). The method detection limits (MDLs) of these amino acids ranged from 1.46 ng L−1 (Proline) to 135 ng L−1 (Arginine), which were much lower than previous methods like high-performance liquid chromatography (HPLC) and comparable to those with liquid chromatography-tandem mass spectrometry (LC-MS/MS). None of the target analytes were detected in blank samples, which was attributed to the optimized pretreatment protocol we adopted. We conclude that the GC–MS based technique developed in this study possesses advantage due to low detection limits. We further demonstrate the applicability of this method by analyzing rain samples from the background atmosphere of the Tibetan Plateau (TP). Similar relative abundances of amino acids were found in the TP rains, marine rains and Arctic ice. The correlations between FAAs and water- soluble ions in the Tibetan Plateau rainwaters showed that the FAAs were most likely originated from biomass burning. Given the similarity of snow and rain samples, our method also provides potential for the future analysis of amino acids in glacier ice cores.

Atmospheric Nitrous Oxide Variations on Centennial Time Scales During the Past Two Millennia

AbstractThe continuous growth of atmospheric nitrous oxide (N2O) is of concern for its potential role in global warming and future stratospheric ozone destruction. Climate feedbacks that enhance N2O emissions in response to global warming are not well understood, and past records of N2O from ice cores are not sufficiently well resolved to examine the underlying climate‐N2O feedbacks on societally relevant time scales. Here, we present a new high‐resolution and high‐precision N2O reconstruction obtained from the Greenland NEEM (North Greenland Eemian Ice Drilling) and the Antarctic Styx Glacier ice cores. Covering the N2O history of the past two millennia, our reconstruction shows a centennial‐scale variability of ~10 ppb. A pronounced minimum at ~600 CE coincides with the reorganizations of tropical hydroclimate and ocean productivity changes. Comparisons with proxy records suggest association of centennial‐ to millennial‐scale variations in N2O with changes in tropical and subtropical land hydrology and marine productivity.

Reconstruction of mining activities in the Western Alps during the past 2500 years from natural archives

The geochemical analysis of natural archives can improve our knowledge of past mining activities and their environmental imprint. The sedimentary records from the Hasli-Aare floodplain (Bernese Alps) over the last 2500 years were analysed for metals. Evidence of past mining contamination was obtained from the XRF analyses of iron, copper, zinc and lead. These results were analytically and statistically processed to produce a metal content index. Positive metal anomalies indicate four major pulses of contamination coinciding with the end of the Iron Age, from the end of the Roman Period to the Early Medieval Period, the Late Medieval Period, and the Modern Period. These pulses show good agreement with local historical sources of mining in the Hasli-Aare catchment, dating back to the beginning of the 15th century. Furthermore, they are in phase with anthropogenic pollution trends inferred from glacier ice cores, lake sediments and peat bogs across the Western Alps, most notably during the Roman, Late Medieval and Modern Periods. However, close comparison between these records can show some differences, suggesting local variations in mining activities and/or a lag in metal transfer. The reconstructed periods of anthropogenic metal pollution are located in their political, economic and social contexts and compared with the climate periods of central Europe.

Gruben glacier and rock glacier, Wallis, Switzerland: glacier ice exposures and their interpretation

ABSTRACTField observations, map analysis and the use of terrestrial and aerial photography and Google Earth show that the Gruben rock glacier, discussed in the literature since 1974, does contain a glacier ice core. Mapped as bare glacier ice at the time of the first map, about AD 1850, subsequent cover by debris from the surrounding cliffs has preserved what is now a slow-moving glacier core beneath a debris cover about 0.5 m thick. Formerly, the steeper and thicker glacier moved debris to the snout much more rapidly than at the present flow rates. The, adjacent, and once co-flowing, tongue of glacier ice was sparsely covered and has down-wasted substantially since the Little Ice Age (ca AD 1850) maximum. Surface down-wasting, surface lakes, ice exposures, and snout recession indicate that the rock glacier’s volume is reducing by wastage of the glacier ice core. This reduction in thickness and surface slope over the last 150 years is sufficient to explain all the observed phenomena in the Gruben basin and present-day low (<1 ma−1) rock glacier surface velocities. Further exposures of glacier ice in the rock glacier are expected with increasing ‘climatic warming’. These findings suggest that the ‘permafrost’ origin of rock glaciers should be re-evaluated.

Imaging the impurity distribution in glacier ice cores with LA-ICP-MS

The novel combination of ice core LA-ICP-MS with improved imaging techniques reveals impurity localization without artifacts.

A Comprehensive Nontarget Analysis for the Molecular Reconstruction of Organic Aerosol Composition from Glacier Ice Cores.

Ice cores are climate archives suitable for the reconstruction of past atmospheric composition changes. Ice core analysis provides valuable insight into the chemical nature of aerosols and enables constraining emission inventories of primary emissions and of gas-phase precursors. Changes in the emissions of volatile organic compounds (VOCs) can affect formation rates and mechanisms as well as chemical composition of aerosols during the preindustrial era, key information for understanding aerosol climate effects. Here, we present an analytical method for the reconstruction of organic aerosol composition preserved in glacier ice cores. A solid-phase-extraction method, optimized toward oxidation products of biogenic VOCs, provides an enrichment factor of ∼200 and quantitative recovery for compounds of interest. We applied the preconcentration method on ice core samples from the high-alpine Fiescherhorn glacier (Swiss Alps), and used high-performance liquid chromatography coupled to high-resolution mass spectrometry as a sensitive detection method. We describe a nontarget analysis that screens for organic molecules in the ice core samples. We evaluate the atmospheric origin of the detected compounds in the ice by molecular-resolved comparison with airborne particulate matter samples from the nearby high-alpine research station Jungfraujoch. The presented method is able to shed light upon the history of the evolution of organic aerosol composition in the anthropocene, a research field in paleoclimatology with considerable potential.

High-Precision Measurement of N2O Concentration in Ice Cores.

Atmospheric nitrous oxide (N2O) is a greenhouse gas and ozone-depleting substance whose emissions are substantially perturbed by current human activities. Although air trapped in polar ice cores can provide direct information about N2O evolution, analytical precision was not previously sufficient for high temporal resolution studies. In this work, we present a highly improved analytical technique with which to study N2O concentrations in ancient-air-trapped ice cores. We adopt a melt-refreezing method to extract air and use a gas chromatography-electron capture detector (GC-ECD) to determine N2O concentrations. The GC conditions are optimized to improve the sensitivity for detecting N2O. Retrapped N2O in ice during the extraction procedure is precisely analyzed and corrected. We confirmed our results using data from the Styx Glacier ice core in Antarctica by comparing them with the results of a dry-extraction method. The precision estimated from the pooled standard deviation of replicated measurements of the Styx ice core was 1.5 ppb for ∼20 g of ice, a smaller sample of ice than was used in previous studies, showing a significant improvement in precision. Our preliminary results from the Styx Glacier ice core samples have the potential to define small N2O variations (a few parts per billion) at centennial time scales.

A New Multielement Method for LA-ICP-MS Data Acquisition from Glacier Ice Cores

To answer pressing new research questions about the rate and timing of abrupt climate transitions, a robust system for ultrahigh-resolution sampling of glacier ice is needed. Here, we present a multielement method of LA-ICP-MS analysis wherein an array of chemical elements is simultaneously measured from the same ablation area. Although multielement techniques are commonplace for high-concentration materials, prior to the development of this method, all LA-ICP-MS analyses of glacier ice involved a single element per ablation pass or spot. This new method, developed using the LA-ICP-MS system at the W. M. Keck Laser Ice Facility at the University of Maine Climate Change Institute, has already been used to shed light on our flawed understanding of natural levels of Pb in Earth's atmosphere.

Hymenobacter frigidus sp. nov., isolated from a glacier ice core.

A psychrophilic, Gram-stain-negative, rod-shaped, red-pigmented bacterium, designated strain B1789T, was isolated from an ice core of Muztagh Glacier on the Tibetan Plateau in China. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain B1789T was related to members of the genus Hymenobacter and had highest sequence similarity with Hymenobacter antarcticus JCM 17217T (97.9 %). The major menaquinone was MK-7 and the major polar lipid was phosphatidylethanolamine. The predominant fatty acids were iso-C15 : 0, anteiso-C15 : 0 and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c). The DNA G+C content was 59.4 mol%. In DNA-DNA hybridization tests, strain B1789T shared 42 % relatedness with H. antarcticus JCM 17217T. Based on the results of phenotypic and chemotaxonomic tests, strain B1789T was considered as representing a novel species of the genus Hymenobacter, for which the name Hymenobacter frigidus sp. nov. is proposed. The type strain is B1789T (=JCM 30595T=CGMCC 1.14966T).

Application of electrical tomography to study the internal structure of rock glaciers in Altai

Internal structure of rock glaciers was investigated at two key sites in Altai by means of electric tomography. It had been found that the rock glaciers of the same type, located at different altitude levels, differ in electric resistances of ice nuclei and the degree of consolidation of the ice material inside of them. Typical characteristics of the ice core of a rock glacier in the high-mountain area are the following: electrical resistivity is about 1000–2000 kOhm∙m and a high degree of the ice consolidation, while the same for the mid-mountain region: the electrical resistivity is 150–300 kOhm∙m and the presence of the talik zones within the glacier body. Using the method of electric tomography for investigation of the internal structure of the rock-glaciers makes possible to reveal presence of frozen soils and ice and to find the upper boundary of occurrence of them from anomalously high specific electric resistance. However, it is not always possible to determine a thickness of the rock-ice formation, and to estimate a degree of its consolidation that does not allow calculating the ice content volume. Limitations of this technology can be overcome by the use of electric tomography in combination with other geophysical methods.

Historical variations of mercury stable isotope ratios in Arctic glacier firn and ice cores

AbstractThe concentration and isotopic composition of mercury (Hg) were determined in glacier core samples from Canadian Arctic ice caps dating from preindustrial to recent time (early 21st century). Mean Hg levels increased from ≤ 0.2 ng L−1 in preindustrial time to ~0.8–1.2 ng L−1 in the modern industrial era (last ~200 years). Hg accumulated on Arctic ice caps has Δ199Hg and Δ201Hg that are higher (~ −1 to 2.9‰) than previously reported for Arctic snow impacted by atmospheric Hg depletion events (mostly &lt; −1‰), suggesting that these events contribute little to Hg accumulation on ice caps. The range of δ202Hg, Δ199Hg, and Δ201Hg in glacier cores overlaps with that of Arctic Hg0(g) and of seawater in Baffin Bay and also with that of midlatitude precipitation and industrial Hg sources, including coal and Hg ores. A core from Agassiz ice cap (80.7°N) shows a ~ +1‰ shift in δ202Hg over the nineteenth to twentieth centuries that could reflect changes in the isotopic composition of the atmospheric Hg pool in the High Arctic in response to growing industrial emissions at lower latitudes. This study is the first ever to report on historical variations of Hg stable isotope ratios in Arctic ice cores. Results could help constrain future modeling efforts of the global Hg biogeochemical cycle and the atmosphere's response to changing Hg emissions, past and future.

Atmospheric Mercury Depositional Chronology Reconstructed from Lake Sediments and Ice Core in the Himalayas and Tibetan Plateau.

Alpine lake sediments and glacier ice cores retrieved from high mountain regions can provide long-term records of atmospheric deposition of anthropogenic contaminants such as mercury (Hg). In this study, eight lake sediment cores and one glacier ice core were collected from high elevations across the Himalaya-Tibet region to investigate the chronology of atmospheric Hg deposition. Consistent with modeling results, the sediment core records showed higher Hg accumulation rates in the southern slopes of the Himalayas than those in the northern slopes in the recent decades (post-World War II). Despite much lower Hg accumulation rates obtained from the glacier ice core, the temporal trend in the Hg accumulation rates matched very well with that observed from the sediment cores. The combination of the lake sediments and glacier ice core allowed us to reconstruct the longest, high-resolution atmospheric Hg deposition chronology in High Asia. The chronology showed that the Hg deposition rate was low between the 1500s and early 1800, rising at the onset of the Industrial Revolution, followed by a dramatic increase after World War II. The increasing trend continues to the present-day in most of the records, reflecting the continuous increase in anthropogenic Hg emissions from South Asia.

Psychrobacter glaciei sp. nov., isolated from the ice core of an Arctic glacier.

A Gram-stain-negative, non-motile, non-spore-forming, non-pigmented, oxidase- and catalase-positive bacterial strain, designated BIc20019T, was isolated from the ice core of Austre Lovénbreen in Ny-Ålesund, Svalbard. The temperature and NaCl ranges for growth were 4-34 °C (optimum, 25-29 °C) and 0-8% (w/v) (optimum, 2-4%). Analysis of the 16S rRNA gene sequence indicated that strain BIc20019T belonged to the genus Psychrobacter and was closely related to Psychrobacter arcticus 273-4T, Psychrobacter cryohalolentis K5T, 'Psychrobacter fjordensis' BSw21516B, Psychrobacter fozii LMG 21280T, Psychrobacter luti LMG 21276T and Pyschrobacter okhotskensis MD17T at greater than 99% similarity. Phylogenetic analysis based on gyrB gene sequences revealed highest similarity (93.6%) to P. okhotskensis MD17T. However, DNA hybridization experiments revealed a low level of DNA-DNA relatedness (<59%) between strain BIc20019T and its closest relatives. Strain BIc20019T contained ubiquinone-8 (Q-8) as the predominant respiratory quinone, and C18:1ω9c and summed feature 3 (C16:1ω7c and/or iso-C15:0 2-OH) as the major fatty acids. It had a DNA G+C content of 46.3 mol%. The polar lipid profile of strain BIc20019T was mainly composed of phosphatidylglycerol, phosphatidylethanolamine and diphosphatidylglycerol. Owing to the differences in phenotypic and chemotaxonomic characteristics, phylogenetic analysis based on 16S rRNA gene and gyrB gene sequences, and DNA-DNA relatedness data, the isolate merits classification within a novel species for which the name Psychrobacter glaciei sp. nov. is proposed. The type strain is BIc20019T (=KCTC 42280T = CCTCC AB 2014019T).