Improving accuracy and precision of ice core δD (CH&lt;sub&gt;4&lt;/sub&gt;) analyses using methane pre- and hydrogen post-pyrolysis trapping and subsequent chromatographic separation

Abstract. Firn and polar ice cores offer the only direct paleoatmospheric archive. Analyses of past greenhouse gas concentrations and their isotopic compositions in air bubbles in the ice can help to constrain changes in global biogeochemical cycles in the past. For the analysis of the hydrogen isotopic composition of methane (δD (CH4)) 0.5 to 1.5 kg of ice was previously necessary to achieve the required precision. Here we present a method to improve precision and reduce the sample amount for δD (CH4) measurements on (ice core) air. Pre-concentrated methane is focused before a high temperature oven (pre pyrolysis trapping), and molecular hydrogen formed by pyrolysis is trapped afterwards (post pyrolysis trapping), both on a carbon-PLOT capillary at −196 °C. A small amount of methane and krypton are trapped together with H2 and must be separated using a short second chromatographic column to ensure accurate results. Pre and post pyrolysis trapping largely removes the isotopic fractionation induced during chromatographic separation and results in a narrow peak in the mass spectrometer. Air standards can be measured with a precision better than 1‰. For polar ice samples from glacial periods we estimate a precision of 2.2‰ for 350 g of ice (or roughly 30 mL (at standard temperature and pressure (STP)) of air) with 350 ppb of methane. This corresponds to recent tropospheric air samples (about 1900 ppb CH4) of about 6 mL (STP) or about 500 pmol of pure CH4.

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Improving accuracy and precision of ice core δD(CH4) analyses using methane pre-pyrolysis and hydrogen post-pyrolysis trapping and subsequent chromatographic separation

Atmospheric Measurement Techniques ◽

10.5194/amt-7-1999-2014 ◽

2014 ◽

Vol 7 (7) ◽

pp. 1999-2012 ◽

Cited By ~ 11

Author(s):

M. Bock ◽

J. Schmitt ◽

J. Beck ◽

R. Schneider ◽

H. Fischer

Keyword(s):

Chromatographic Separation ◽

Ice Core ◽

Isotopic Fractionation ◽

Ice Cores ◽

Polar Ice ◽

Accuracy And Precision ◽

Sample Amount ◽

Global Biogeochemical Cycles ◽

Improving Accuracy ◽

Glacial Periods

Abstract. Firn and polar ice cores offer the only direct palaeoatmospheric archive. Analyses of past greenhouse gas concentrations and their isotopic compositions in air bubbles in the ice can help to constrain changes in global biogeochemical cycles in the past. For the analysis of the hydrogen isotopic composition of methane (δD(CH4) or δ2H(CH4)) 0.5 to 1.5 kg of ice was hitherto used. Here we present a method to improve precision and reduce the sample amount for δD(CH4) measurements in (ice core) air. Pre-concentrated methane is focused in front of a high temperature oven (pre-pyrolysis trapping), and molecular hydrogen formed by pyrolysis is trapped afterwards (post-pyrolysis trapping), both on a carbon-PLOT capillary at −196 °C. Argon, oxygen, nitrogen, carbon monoxide, unpyrolysed methane and krypton are trapped together with H2 and must be separated using a second short, cooled chromatographic column to ensure accurate results. Pre- and post-pyrolysis trapping largely removes the isotopic fractionation induced during chromatographic separation and results in a narrow peak in the mass spectrometer. Air standards can be measured with a precision better than 1‰. For polar ice samples from glacial periods, we estimate a precision of 2.3‰ for 350 g of ice (or roughly 30 mL – at standard temperature and pressure (STP) – of air) with 350 ppb of methane. This corresponds to recent tropospheric air samples (about 1900 ppb CH4) of about 6 mL (STP) or about 500 pmol of pure CH4.

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Global biosphere primary productivity over the last 800,000 years reconstructed from the triple-isotope composition of dioxygen trapped in polar ice cores

10.5194/egusphere-egu21-12552 ◽

2021 ◽

Author(s):

Ji-Woong Yang ◽

Amaëlle Landais ◽

Margaux Brandon ◽

Thomas Blunier ◽

Frédéric Prié ◽

...

Keyword(s):

Primary Productivity ◽

Isotope Composition ◽

Atmospheric Oxygen ◽

Ice Cores ◽

Oxygenic Photosynthesis ◽

Time Interval ◽

Polar Ice ◽

Future Evolution ◽

Glacial Stage ◽

Glacial Periods

The primary production, or oxygenic photosynthesis of the global biosphere, is one of the main source and sink of atmospheric oxygen (O2) and carbon dioxide (CO2), respectively. There has been a growing number of evidence that global gross primary productivity (GPP) varies in response to climate change. It is therefore important to understand the climate- and/or environment controls of the global biosphere primary productivity for better predicting the future evolution of biosphere carbon uptake. The triple-isotope composition of O2 (&#916;17O of O2) trapped in polar ice cores allows us to trace the past changes of global biosphere primary productivity as far back as 800,000 years before present (800 ka). Previously available &#916;17O of O2 records over the last ca. 450 ka show relatively low and high global biosphere productivity over the last five glacial and interglacial intervals respectively, with a unique pattern over Termination V (TV) - Marine Isotopic Stage (MIS) 11, as biosphere productivity at the end of TV is ~ 20 % higher than the four younger ones (Blunier et al., 2012; Brandon et al., 2020). However, questions remain on (1) whether the concomitant changes of global biosphere productivity and CO2 were the pervasive feature of glacial periods over the last 800 ka, and (2) whether the global biosphere productivity during the &#8220;lukewarm&#8221; interglacials before the Mid-Brunhes Event (MBE) were lower than those after the MBE. Here, we present an extended composite record of &#916;17O of O2 covering the last 800 ka, based on new &#916;17O of O2 results from the EPICA Dome C and reconstruct the evolution of global biosphere productivity over that time interval using the independent box models of Landais et al. (2007) and Blunier et al. (2012). We find that the glacial productivity minima occurred nearly synchronously with the glacial CO2 minima at mid-glacial stage; interestingly millennia before the sea level reaches their minima. Following the mid-glacial minima, we also show slight productivity increases at the full-glacial stages, before deglacial productivity rises. Comparison of reconstructed interglacial productivity demonstrates a slightly higher productivity over the post-MBE (MISs 1, 5, 7, 9, and 11) than pre-MBE ones (MISs 13, 15, 17, and 19). However, the mean difference between post- and pre-MBE interglacials largely depends on the box model used for productivity reconstruction.

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Polar ice stratigraphy from laser-light scattering: scattering from meltwater

Journal of Glaciology ◽

10.1017/s0022143000012387 ◽

1994 ◽

Vol 40 (136) ◽

pp. 504-508 ◽

Cited By ~ 17

Author(s):

Michael Ram ◽

Matthias Illing

Keyword(s):

Light Scattering ◽

Sample Size ◽

Tree Ring ◽

Laser Light ◽

Ice Core ◽

Ice Cores ◽

Laser Light Scattering ◽

Polar Ice ◽

The Core ◽

Considerable Success

Abstract We describe a new laser-light-scattering instrument for measuring variations in dust concentration along polar ice cores. We have used this instrument with considerable success on the GISP2 ice core from central Greenland. Reproducibility is excellent and the required ice-sample size is relatively small. When combined with visual stratigraphy and ECM, the distinct annual spring/ summer dust peaks we observe can be used to date the core with tree-ring-like precision.

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Towards radiocarbon dating of ice cores

Journal of Glaciology ◽

10.3189/002214309790794922 ◽

2009 ◽

Vol 55 (194) ◽

pp. 985-996 ◽

Cited By ~ 33

Author(s):

M. Sigl ◽

T.M. Jenk ◽

T. Kellerhals ◽

S. Szidat ◽

H.W. Gäggeler ◽

...

Keyword(s):

Aerosol Particles ◽

Ice Core ◽

Ice Cores ◽

Swiss Alps ◽

Carbonaceous Aerosol ◽

Polar Ice ◽

Low Latitude ◽

Bolivian Andes ◽

Glacier Ice ◽

Dating Method

AbstractA recently developed dating method for glacier ice, based on the analysis of radiocarbon in carbonaceous aerosol particles, is thoroughly investigated. We discuss the potential of this method to achieve a reliable dating using examples from a mid- and a low-latitude ice core. Two series of samples from Colle Gnifetti (4450 m a.s.l., Swiss Alps) and Nevado Illimani (6300 m a.s.l., Bolivian Andes) demonstrate that the 14C ages deduced from the water-insoluble organic carbon fraction represent the age of the ice. Sample sizes ranged between 7 and 100 μg carbon. For validation we compare our results with those from independent dating. This new method is thought to have major implications for dating non-polar ice cores in the future, as it provides complementary age information for time periods not accessible with common dating techniques.

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Environmental records from polar ice cores

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1990.0026 ◽

1990 ◽

Vol 330 (1615) ◽

pp. 459-462 ◽

Cited By ~ 1

Keyword(s):

Solar Activity ◽

Ice Core ◽

Ice Cores ◽

Polar Ice ◽

Cosmogenic Isotope ◽

Wide Range ◽

Recent Part ◽

Ice Core Records

Polar ice cores provide a wide range of information on past atmospheric climate (temperature, precipitation) and environment (gas and aerosol concentrations). The dating can be very accurate for the more recent part of the records but accuracy decreases with depth and time. Measurements of cosmogenic isotope concentrations (such as 10 Be) provide information on palaeo-precipitation rates and particular events can be used to correlate ice core records. Besides these climatic applications, 10 Be concentration records in ice cores also contain information on solar activity changes.

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Grain Growth in Polar Ice: II. Application

Journal of Glaciology ◽

10.1017/s0022143000012132 ◽

1986 ◽

Vol 32 (112) ◽

pp. 425-433 ◽

Cited By ~ 84

Author(s):

R.B. Alley ◽

J.H. Perepezko ◽

C.R. Bentley

Keyword(s):

Grain Boundaries ◽

Grain Growth ◽

Growth Rates ◽

Boundary Migration ◽

Ice Core ◽

Ice Cores ◽

Geometric Constraints ◽

Polar Ice ◽

High Concentration ◽

Micro Particles

AbstractGrain growth observed in polar ice that is not deforming rapidly can be accounted for if concentrations and distributions of extrinsic materials (microparticles, bubbles, and dissolved impurities) are characterized fully. Dissolved impurities segregate to grain boundaries and slow grain growth in all cold glacial ice. The high concentration of soluble impurities in Wisconsinan ice from the Dome C (Antarctica) ice core (and perhaps other ice cores) probably causes the small grain-sizes observed in that ice. Microparticles have little effect on grain growth in ordinary ice. In ice layers that appear dirty owing to concentrations of volcanic tephra (such as in the Byrd Station (Antarctica) ice core) or of morainal material, micro particles reduce grain-growth rates significantly. The relatively high vapor pressure of ice allows rapid growth and high mobility of intergranular necks, so grain growth in firn is limited by boundary migration rather than by neck growth. Bubbles formed by pore close-off at the firn-ice transition are less mobile than grain boundaries, causing bubble-boundary separation whenever geometric constraints are satisfied; however, such separation reduces grain-growth rates by only about 10%. The observed linear increase of grain area with time is thus predicted by theory, but the growth rate depends on soluble-impurity concentrations as well as on temperature.

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An optimized multi-proxy, multi-site Antarctic ice and gas orbital chronology (AICC2012): 120–800 ka

Climate of the Past ◽

10.5194/cp-9-1715-2013 ◽

2013 ◽

Vol 9 (4) ◽

pp. 1715-1731 ◽

Cited By ~ 216

Author(s):

L. Bazin ◽

A. Landais ◽

B. Lemieux-Dudon ◽

H. Toyé Mahamadou Kele ◽

D. Veres ◽

...

Keyword(s):

Ice Core ◽

Ice Cores ◽

Companion Paper ◽

Polar Ice ◽

Uncertainty Range ◽

Air Content ◽

Dating Method ◽

Long Timescales ◽

Age Constraints ◽

Mis 5

Abstract. An accurate and coherent chronological framework is essential for the interpretation of climatic and environmental records obtained from deep polar ice cores. Until now, one common ice core age scale had been developed based on an inverse dating method (Datice), combining glaciological modelling with absolute and stratigraphic markers between 4 ice cores covering the last 50 ka (thousands of years before present) (Lemieux-Dudon et al., 2010). In this paper, together with the companion paper of Veres et al. (2013), we present an extension of this work back to 800 ka for the NGRIP, TALDICE, EDML, Vostok and EDC ice cores using an improved version of the Datice tool. The AICC2012 (Antarctic Ice Core Chronology 2012) chronology includes numerous new gas and ice stratigraphic links as well as improved evaluation of background and associated variance scenarios. This paper concentrates on the long timescales between 120–800 ka. In this framework, new measurements of δ18Oatm over Marine Isotope Stage (MIS) 11–12 on EDC and a complete δ18Oatm record of the TALDICE ice cores permit us to derive additional orbital gas age constraints. The coherency of the different orbitally deduced ages (from δ18Oatm, δO2/N2 and air content) has been verified before implementation in AICC2012. The new chronology is now independent of other archives and shows only small differences, most of the time within the original uncertainty range calculated by Datice, when compared with the previous ice core reference age scale EDC3, the Dome F chronology, or using a comparison between speleothems and methane. For instance, the largest deviation between AICC2012 and EDC3 (5.4 ka) is obtained around MIS 12. Despite significant modifications of the chronological constraints around MIS 5, now independent of speleothem records in AICC2012, the date of Termination II is very close to the EDC3 one.

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EBSD analysis of subgrain boundaries and dislocation slip systems in Antarctic and Greenland ice

Solid Earth ◽

10.5194/se-8-883-2017 ◽

2017 ◽

Vol 8 (5) ◽

pp. 883-898 ◽

Cited By ~ 7

Author(s):

Ilka Weikusat ◽

Ernst-Jan N. Kuiper ◽

Gill M. Pennock ◽

Sepp Kipfstuhl ◽

Martyn R. Drury

Keyword(s):

Basal Slip ◽

Plastic Anisotropy ◽

Ice Core ◽

Ice Cores ◽

Dislocation Slip ◽

Slip Systems ◽

Polar Ice ◽

Electron Backscattered Diffraction ◽

Depth Level ◽

Core Samples

Abstract. Ice has a very high plastic anisotropy with easy dislocation glide on basal planes, while glide on non-basal planes is much harder. Basal glide involves dislocations with the Burgers vector b = 〈a〉, while glide on non-basal planes can involve dislocations with b = 〈a〉, b = [c], and b = 〈c + a〉. During the natural ductile flow of polar ice sheets, most of the deformation is expected to occur by basal slip accommodated by other processes, including non-basal slip and grain boundary processes. However, the importance of different accommodating processes is controversial. The recent application of micro-diffraction analysis methods to ice, such as X-ray Laue diffraction and electron backscattered diffraction (EBSD), has demonstrated that subgrain boundaries indicative of non-basal slip are present in naturally deformed ice, although so far the available data sets are limited. In this study we present an analysis of a large number of subgrain boundaries in ice core samples from one depth level from two deep ice cores from Antarctica (EPICA-DML deep ice core at 656 m of depth) and Greenland (NEEM deep ice core at 719 m of depth). EBSD provides information for the characterization of subgrain boundary types and on the dislocations that are likely to be present along the boundary. EBSD analyses, in combination with light microscopy measurements, are presented and interpreted in terms of the dislocation slip systems. The most common subgrain boundaries are indicative of basal 〈a〉 slip with an almost equal occurrence of subgrain boundaries indicative of prism [c] or 〈c + a〉 slip on prism and/or pyramidal planes. A few subgrain boundaries are indicative of prism 〈a〉 slip or slip of 〈a〉 screw dislocations on the basal plane. In addition to these classical polygonization processes that involve the recovery of dislocations into boundaries, alternative mechanisms are discussed for the formation of subgrain boundaries that are not related to the crystallography of the host grain.The finding that subgrain boundaries indicative of non-basal slip are as frequent as those indicating basal slip is surprising. Our evidence of frequent non-basal slip in naturally deformed polar ice core samples has important implications for discussions on ice about plasticity descriptions, rate-controlling processes which accommodate basal glide, and anisotropic ice flow descriptions of large ice masses with the wider perspective of sea level evolution.

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Polar ice stratigraphy from laser-light scattering: scattering from meltwater

Journal of Glaciology ◽

10.3189/s0022143000012387 ◽

1994 ◽

Vol 40 (136) ◽

pp. 504-508

Author(s):

Michael Ram ◽

Matthias Illing

Keyword(s):

Light Scattering ◽

Sample Size ◽

Tree Ring ◽

Laser Light ◽

Ice Core ◽

Ice Cores ◽

Laser Light Scattering ◽

Polar Ice ◽

The Core ◽

Considerable Success

AbstractWe describe a new laser-light-scattering instrument for measuring variations in dust concentration along polar ice cores. We have used this instrument with considerable success on the GISP2 ice core from central Greenland. Reproducibility is excellent and the required ice-sample size is relatively small. When combined with visual stratigraphy and ECM, the distinct annual spring/ summer dust peaks we observe can be used to date the core with tree-ring-like precision.

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