Raman spectroscopy of gaseous inclusions in EDML ice core: first results – microbubbles

Weikusat, Christian; Freitag, Johannes; Kipfstuhl, Sepp

doi:10.3189/2012jog11j222

Cited by 13 publications

(17 citation statements)

References 30 publications

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“…Direct measurement of the air composition in these small inclusion is only possible for the main air constituents N 2 and O 2 using Raman spectroscopy. Such measurements show an enrichment of O 2 in these features [ Weikusat et al , ; Nedelcu et al , ]. Following the understanding of the BCTZ, this phenomenon could be explained by drawing on the fact that freshly formed relaxation features fill up preferentially with O 2 as it permeates faster through the ice lattice from the neighboring clathrate hydrates.…”

Section: Discussionmentioning

confidence: 99%

Revision of the EPICA Dome C CO₂ record from 800 to 600 kyr before present

Bereiter

Eggleston

Schmitt

et al. 2015

Geophysical Research Letters

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667

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The European Project for Ice Coring in Antarctica Dome ice core from Dome C (EDC) has allowed for the reconstruction of atmospheric CO 2 concentrations for the last 800,000 years. Here we revisit the oldest part of the EDC CO 2 record using different air extraction methods and sections of the core. For our established cracker system, we found an analytical artifact, which increases over the deepest 200 m and reaches 10.1 ± 2.4 ppm in the oldest/deepest part. The governing mechanism is not yet fully understood, but it is related to insufficient gas extraction in combination with ice relaxation during storage and ice structure. The corrected record presented here resolves partly -but not completely -the issue with a different correlation between CO 2 and Antarctic temperatures found in this oldest part of the records. In addition, we provide here an update of 800,000 years atmospheric CO 2 history including recent studies covering the last glacial cycle.

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Section: Discussionmentioning

confidence: 99%

Revision of the EPICA Dome C CO₂ record from 800 to 600 kyr before present

Bereiter

Eggleston

Schmitt

et al. 2015

Geophysical Research Letters

Self Cite

618

667

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“…In both EDML samples we observe high accumulations of secondary gas inclusions along grain boundaries, which are formed due to relaxation of the material (Weikusat et al, 2012). Their high densities allow us to partly reconstruct the 3-D shape of the grain boundary just by means of the microbubbles (Figs.…”

Section: Distribution With Respect To Microstructurementioning

confidence: 95%

“…Impurity map with marked µ inclusions (yellow circles) and grain boundary network from the surface map. Roundish black objects with the size of several tens of µm are secondary gas inclusions (micro-bubbles) formed due to relaxation (Weikusat et al, 2012). While µ inclusions follow horizontal layering, micro-bubbles trace the 3-D shape of the grain boundaries.…”

Section: Raman Spectroscopymentioning

confidence: 99%

“…(2) Another option is that the "black dots" at grain boundaries observed by Faria et al (2010) in fact are small micro-bubbles forming due the abrupt drop of pressure after logging the ice core. Weikusat et al (2012) analyzed compositions of secondary microbubbles using Raman spectroscopy. The authors also remark that secondary bubbles tend to form at locations of "black dots".…”

Section: Zener Pinningmentioning

confidence: 99%

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Location and distribution of micro-inclusions in the EDML and NEEM ice cores using optical microscopy and in situ Raman spectroscopy

et al. 2017

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Abstract. Impurities control a variety of physical properties of polar ice. Their impact can be observed at all scalesfrom the microstructure (e.g., grain size and orientation) to the ice sheet flow behavior (e.g., borehole tilting and closure). Most impurities in ice form micrometer-sized inclusions. It has been suggested that these µ inclusions control the grain size of polycrystalline ice by pinning of grain boundaries (Zener pinning), which should be reflected in their distribution with respect to the grain boundary network. We used an optical microscope to generate high-resolution large-scale maps (3 µm pix −1 , 8×2 cm 2 ) of the distribution of micro-inclusions in four polar ice samples: two from Antarctica (EDML, MIS 5.5) and two from Greenland (NEEM, Holocene). The in situ positions of more than 5000 µ inclusions have been determined. A Raman microscope was used to confirm the extrinsic nature of a sample proportion of the mapped inclusions. A superposition of the 2-D grain boundary network and µ-inclusion distributions shows no significant correlations between grain boundaries and µ inclusions. In particular, no signs of grain boundaries harvesting µ inclusions could be found and no evidence of µ inclusions inhibiting grain boundary migration by slow-mode pinning could be detected. Consequences for our understanding of the impurity effect on ice microstructure and rheology are discussed.

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“…The method was also applied on-site immediately after drilling (in 2003 for the EDML and in 2010 for the NEEM samples). This method allowed us to monitor any microstructural changes caused by pressure and temperature change during transportation and storage (Miyamoto et al, 2009;Weikusat et al, 2012) and to locate regions of interest for EBSD, particularly as the subgrain microstructures were heterogeneously distributed. The c-axes and CPO were measured in the depth ranges of the EBSD samples with an automated fabric analyser system of the Australian Russell-Head type (Peternell et al, 2010).…”

Section: Methodsmentioning

confidence: 99%

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

et al. 2017

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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 nonbasal 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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Raman spectroscopy of gaseous inclusions in EDML ice core: first results – microbubbles

Cited by 13 publications

References 30 publications

Revision of the EPICA Dome C CO₂ record from 800 to 600 kyr before present

Revision of the EPICA Dome C CO₂ record from 800 to 600 kyr before present

Location and distribution of micro-inclusions in the EDML and NEEM ice cores using optical microscopy and in situ Raman spectroscopy

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

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Raman spectroscopy of gaseous inclusions in EDML ice core: first results – microbubbles

Cited by 13 publications

References 30 publications

Revision of the EPICA Dome C CO2 record from 800 to 600 kyr before present

Revision of the EPICA Dome C CO2 record from 800 to 600 kyr before present

Location and distribution of micro-inclusions in the EDML and NEEM ice cores using optical microscopy and in situ Raman spectroscopy

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

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Revision of the EPICA Dome C CO₂ record from 800 to 600 kyr before present

Revision of the EPICA Dome C CO₂ record from 800 to 600 kyr before present