scholarly journals The Contribution of Synchrotron Light for the Characterization of Atmospheric Mineral Dust in Deep Ice Cores: Preliminary Results from the Talos Dome Ice Core (East Antarctica)

2018 ◽  
Vol 3 (3) ◽  
pp. 25 ◽  
Author(s):  
Giovanni Baccolo ◽  
Giannantonio Cibin ◽  
Barbara Delmonte ◽  
Dariush Hampai ◽  
Augusto Marcelli ◽  
...  
Keyword(s):  
Ice Core ◽  
Ice Cores ◽  
New Techniques ◽  
Preliminary Results ◽  
The Core ◽  
Depositional Processes ◽  
Synchrotron Light ◽  
Climatic Signals

The possibility of finding a stratigraphically intact ice sequence with a potential basal age exceeding one million years in Antarctica is giving renewed interest to deep ice coring operations. But the older and deeper the ice, the more impactful are the post-depositional processes that alter and modify the information entrapped within ice layers. Understanding in situ post-depositional processes occurring in the deeper part of ice cores is essential to comprehend how the climatic signals are preserved in deep ice, and consequently how to construct the paleoclimatic records. New techniques and new interpretative tools are required for these purposes. In this respect, the application of synchrotron light to microgram-sized atmospheric dust samples extracted from deep ice cores is extremely promising. We present here preliminary results on two sets of samples retrieved from the Talos Dome Antarctic ice core. A first set is composed by samples from the stratigraphically intact upper part of the core, the second by samples retrieved from the deeper part of the core that is still undated. Two techniques based on synchrotron light allowed us to characterize the dust samples, showing that mineral particles entrapped in the deepest ice layers display altered elemental composition and anomalies concerning iron geochemistry, besides being affected by inter-particle aggregation.

scholarly journals A stratigraphy-based method for reconstructing ice core orientation

2021 ◽  
Author(s):  
Julien Westhoff ◽  
Nicolas Stoll ◽  
Steven Franke ◽  
Ilka Weikusat ◽  
Paul Bons ◽  
...  
Keyword(s):  
Physical Properties ◽  
Ice Core ◽  
Ice Cores ◽  
The Core ◽  
Ice Stream ◽  
Orientation Method

<p>Ever since the first deep ice cores were drilled, it has been a challenge to determine their original, in-situ orientation. In general, the orientation of an ice core is lost as the drill is free to rotate during transport to the surface. For shallow ice cores, it is usually possible to match the adjacent core breaks, which preserves the orientation of the ice column. However, this method fails for deep ice cores, such as the EastGRIP ice core in Northeast Greenland. We provide a method to reconstruct ice core orientation using visual stratigraphy and borehole geometry. As the EastGRIP ice core is drilled through the Northeast Greenland Ice Stream, we use information about the directional structures to perform a full geographical re-orientation. We compared the core orientation with logging data from core break matching and the pattern of the stereographic projections of the crystals’c-axis orientations. Both comparisons agree very well with the proposed orientation method. The method works well for 441 out of 451 samples from a depth of 1375–2120 m in the EastGRIP ice core. It can also be applied to other ice cores, providing a better foundation for interpreting physical properties and understanding the flow of ice.</p>

scholarly journals A stratigraphy-based method for reconstructing ice core orientation

2020 ◽  
pp. 1-12
Author(s):  
Julien Westhoff ◽  
Nicolas Stoll ◽  
Steven Franke ◽  
Ilka Weikusat ◽  
Paul Bons ◽  
...  
Keyword(s):  
Physical Properties ◽  
Ice Core ◽  
Ice Cores ◽  
The Core ◽  
Ice Stream ◽  
Orientation Method

Abstract Ever since the first deep ice cores were drilled, it has been a challenge to determine their original, in-situ orientation. In general, the orientation of an ice core is lost as the drill is free to rotate during transport to the surface. For shallow ice cores, it is usually possible to match the adjacent core breaks, which preserves the orientation of the ice column. However, this method fails for deep ice cores, such as the EastGRIP ice core in Northeast Greenland. We provide a method to reconstruct ice core orientation using visual stratigraphy and borehole geometry. As the EastGRIP ice core is drilled through the Northeast Greenland Ice Stream, we use information about the directional structures to perform a full geographical re-orientation. We compared the core orientation with logging data from core break matching and the pattern of the stereographic projections of the crystals’ c-axis orientations. Both comparisons agree very well with the proposed orientation method. The method works well for 441 out of 451 samples from a depth of 1375–2120 m in the EastGRIP ice core. It can also be applied to other ice cores, providing a better foundation for interpreting physical properties and understanding the flow of ice.

In situsmall-angle X-ray scattering characterization of X-ray-induced local heating

2014 ◽  
Vol 47 (6) ◽  
pp. 2078-2080 ◽  
Author(s):  
Monika Witala ◽  
Jun Han ◽  
Andreas Menzel ◽  
Kim Nygård
Keyword(s):  
Local Heating ◽  
Liquid Mixtures ◽  
Glass Capillary ◽  
Sample Container ◽  
X Ray ◽  
X Ray Scattering ◽  
Synchrotron Light ◽  
Ray Scattering

It is shown that small-angle X-ray scattering from binary liquid mixtures close to the critical point of demixing can be used forin situcharacterization of beam-induced heating of liquid samples. For demonstration purposes, the proposed approach is applied on a well studied critical mixture of water and 2,6-lutidine. Given a typical incident X-ray flux at a third-generation synchrotron light source and using a 1.5 mm-diameter glass capillary as sample container, a beam-induced local temperature increase of 0.45 ± 0.10 K is observed.

scholarly journals Methanesulphonic acid movement in solid ice cores

2004 ◽  
Vol 39 ◽  
pp. 540-544 ◽  
Author(s):  
Barbara T. Smith ◽  
Tas D. Van Ommen ◽  
Mark A. J. Curran
Keyword(s):  
Diffusion Coefficient ◽  
Biological Activity ◽  
Sea Ice ◽  
Diffusion Mechanism ◽  
Ice Core ◽  
Ice Cores ◽  
East Antarctica ◽  
The Core ◽  
Central Value

AbstractMethanesulphonic acid (MSA) is an important trace-ion constituent in ice cores, with connections to biological activity and sea-ice distribution. Post-depositional movement of MSA has been documented in firn, and this study investigates movement in solid ice by measuring variations in MSA distribution across several horizontal sections from an ice core after 14.5 years storage. The core used is from below the bubble close-off depth at Dome Summit South, Law Dome, East Antarctica. MSA concentration was studied at 3 and 0.5 cm resolution across the core widths. Its distribution was uniform through the core centres, but the outer 3 cm showed gradients in concentrations down to less than half of the central value at the core edge. This effect is consistent with diffusion to the surrounding air during its 14.5 year storage. The diffusion coefficient is calculated to be 2 ×10–13 m2 s–1, and the implications for the diffusion mechanism are discussed.

Dating of ice cores from temperate glaciers - Significant mass loss in the accumulation area of the Adamello glacier indicated by the chronology of a 46 m ice core

2021 ◽  
Author(s):  
Theo Jenk ◽  
Daniela Festi ◽  
Margit Schwikowski ◽  
Valter Maggi ◽  
Klaus Oeggl
Keyword(s):  
Mass Loss ◽  
Ice Core ◽  
Ice Cores ◽  
Italian Alps ◽  
Accumulation Zone ◽  
The Core ◽  
Annual Layer ◽  
Significant Mass Loss ◽  
Carbon Concentrations ◽  
Significant Mass

<p>Dating glaciers is an arduous yet essential task in ice core studies, which becomes even more challenging for the dating of glaciers suffering from mass loss in the accumulation zone as result of climate warming. In this context, we present the dating of a 46 m deep ice core from the Central Italian Alps retrieved in 2016 from the Adamello glacier (Pian di Neve, 3100 m a.s.l.). We will show how the timescale for the core could be obtained by integrating results from the analyses of the radionuclides <sup>210</sup>Pb and <sup>137</sup>Cs with annual layer counting derived from pollen and refractory black carbon concentrations. Our results clearly indicate that the surface of the glacier is older than the drilling date of 2016 by about 20 years and that the 46 m ice core reaches back to around 1944. Despite the severe mass loss affecting this glacier even in the accumulation zone, we show that it is possible to obtain a reliable timescale for such a temperate glacier. These results are very encouraging and open new perspectives on the potential of such glaciers as informative palaeoarchives. We thus consider it important to present our dating approach to a broader audience.</p>

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

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

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.

scholarly journals Microstructural characterization of ice cores

2005 ◽  
Vol 42 ◽  
pp. 441-444 ◽  
Author(s):  
Ian Baker ◽  
Daniel Iliescu ◽  
Rachel Obbard ◽  
Hui Chang ◽  
Benjamin Bostick ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Optical Microscopy ◽  
Ice Core ◽  
Ice Cores ◽  
Microstructural Characterization ◽  
Electron Backscatter ◽  
Scanning Electron

AbstractIn this paper, we outline the use of Raman spectroscopy coupled with scanning confocal optical microscopy for determining the microstructural location of impurities in ice-core specimens. We also demonstrate how the orientations of grains and the misorientations across grain boundaries can be determined to high precision for ice polycrystals using either selected area channeling patterns or electron backscatter patterns in a scanning electron microscope.

Diffusion of climatic signals in ice cores by vein migration

2020 ◽  
Author(s):  
Felix S. L. Ng
Keyword(s):  
Grain Growth ◽  
Impurity Concentration ◽  
Diffusion Mechanism ◽  
Ice Core ◽  
Ice Cores ◽  
Spatial Gradient ◽  
Stochastic Motion ◽  
Advection Diffusion Equation ◽  
Peak Broadening ◽  
Climatic Signals

<p>Ice-core analysis shows that climatic signals carried by dissolved impurities (e.g., sulphate) in the water veins exhibit peak broadening and damping with depth into the ice. Such diffusion distorts the signals progressively, limiting the retrievability of the past climatic variations, notably their time resolution. A mechanism put forward for the diffusion invokes continuous differential grain growth in creating gradients in impurity concentration in the vein water (Barnes et al., 2003). Separately, a mechanism known as “anomalous diffusion” has been proposed (Rempel et al., 2001) where vertical temperature gradients in the ice drive the migration of chemical peaks without diffusion — this migration causes age offset between the signals and the ice. Here, we show that climatic signals diffuse because of constant dynamical evolution of the vein network in polycrystalline ice that accompanies grain-boundary migration. In this new mechanism, the stochastic motion of vein segments carrying solute leads to a net diffusive transport of impurities when there is spatial gradient in the bulk impurity concentration or porosity. By modelling this phenomenon with a statistical-mechanical formulation in three dimensions, we find that the diffusivity <em>κ</em> for the bulk impurity concentration is given by <em>κ</em> = <em>K</em>(<em>T</em>)/3c, where <em>K</em> is the temperature-dependent grain growth rate and c (≈ 2 to 3) is a geometry constant, and that <em>κ</em> is independent of the mean grain size. The description of porosity follows an advection-diffusion equation that includes the other processes of Rempel et al. (2001) and Barnes et al. (2003). Our calculations for the Greenland summit ice cores and the EPICA ice core predict diffusivities of <em>κ</em> ∼ 10<sup>–8</sup> – 10<sup>–7 </sup>m<sup>2</sup> yr<sup>–1</sup>, which can explain the observed amount of peak broadening. Further including into this theory the regelative transport of the solute by water flow along the veins reveals a correction of ≈ 10% for the signal migration speed predicted by Rempel et al. (2001). Besides contributing a new diffusion mechanism, our study highlights the importance of grain-scale recrystallisation processes for understanding bulk ice properties.</p>

scholarly journals Extreme snow metamorphism in the Allan Hills, Antarctica, as an analogue for glacial conditions with implications for stable isotope composition

2015 ◽  
Vol 61 (230) ◽  
pp. 1171-1182 ◽  
Author(s):  
Ruzica Dadic ◽  
Martin Schneebeli ◽  
Nancy A.N. Bertler ◽  
Margit Schwikowski ◽  
Margret Matzl
Keyword(s):  
Stable Isotope ◽  
Isotope Composition ◽  
Ice Core ◽  
Initial Density ◽  
Stratigraphic Sequence ◽  
The Core ◽  
Depositional Processes ◽  
Alternating Temperature ◽  
Glacial Periods ◽  
Ice Core Records

AbstractUnderstanding physical processes in near-zero accumulation areas can help us to better understand polar ice-core records, particularly during periods when accumulation rates were lower than today. We report measurements from a 5 m firn core from the Allan Hills, Antarctica, which include physical properties using computer tomography, stable isotope ratios δD and δ18O, and 210Pb activity. The core shows a highly metamorphosed firn with homogeneous and stable structure, but with discrete layers near the surface. The observed firn structure is caused by a combination of unique depositional and post-depositional processes. The irregular δD and δ18O signal does not follow the stratigraphic sequence and implies post-depositional modification caused by microscopic pressure gradients in the firn that can result from either forced ventilation over rough surfaces in the presence of wind or alternating temperature-gradients between the firn and the atmosphere. Our results also indicate impact snow deposition under high winds and with a high initial density and air exchange between the atmosphere and the snowpack.210Pb activity below 0.3 m falls below the detection limit, implying that most of the core is more than 100 years old. We conclude that the Allan Hills record provides a unique opportunity to investigate important processes that would have affected ice-core records from glacial periods.

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

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.

Sign in / Sign up

Export Citation Format

Share Document