scholarly journals Towards orbital dating of the EPICA Dome C ice core using δO<sub>2</sub>/N<sub>2</sub>

2012 ◽  
Vol 8 (1) ◽  
pp. 191-203 ◽  
Author(s):  
A. Landais ◽  
G. Dreyfus ◽  
E. Capron ◽  
K. Pol ◽  
M. F. Loutre ◽  
...  
Keyword(s):  
Ice Core ◽  
Air Bubbles ◽  
Before Present ◽  
Data Filtering ◽  
Tuning Method ◽  
Trapped Air ◽  
Measurement Series ◽  
Orbital Tuning ◽  
Gas Loss ◽  
Grain Properties

Abstract. Based on a composite of several measurement series performed on ice samples stored at −25 °C or −50 °C, we present and discuss the first δO2/N2 record of trapped air from the EPICA Dome C (EDC) ice core covering the period between 300 and 800 ka (thousands of years before present). The samples stored at −25 °C show clear gas loss affecting the precision and mean level of the δO2/N2 record. Two different gas loss corrections are proposed to account for this effect, without altering the spectral properties of the original datasets. Although processes at play remain to be fully understood, previous studies have proposed a link between surface insolation, ice grain properties at close-off, and δO2/N2 in air bubbles, from which orbitally tuned chronologies of the Vostok and Dome Fuji ice core records have been derived over the last four climatic cycles. Here, we show that limitations caused by data quality and resolution, data filtering, and uncertainties in the orbital tuning target limit the precision of this tuning method for EDC. Moreover, our extended record includes two periods of low eccentricity. During these intervals (around 400 ka and 750 ka), the matching between δO2/N2 and the different insolation curves is ambiguous because some local insolation maxima cannot be identified in the δO2/N2 record (and vice versa). Recognizing these limitations, we restrict the use of our δO2/N2 record to show that the EDC3 age scale is generally correct within its published uncertainty (6 kyr) over the 300–800 ka period.

scholarly journals Towards orbital dating of the EPICA Dome C ice core using δO<sub>2</sub>/N<sub>2</sub>

2011 ◽  
Vol 7 (3) ◽  
pp. 2217-2259 ◽  
Author(s):  
A. Landais ◽  
G. Dreyfus ◽  
E. Capron ◽  
K. Pol ◽  
M. F. Loutre ◽  
...  
Keyword(s):  
Data Quality ◽  
Ice Core ◽  
Marine Isotopic Stage ◽  
Tuning Method ◽  
Trapped Air ◽  
Measurement Series ◽  
Orbital Tuning ◽  
Quality Filtering ◽  
Gas Loss ◽  
Grain Properties

Abstract. Based on a composite of several measurement series performed on ice samples stored at −25 °C or −50 °C, we present and discuss the first δO2/N2 record of trapped air from the EPICA Dome C (EDC) ice core covering the period between 300 and 800 ka (thousands of years before present). The samples stored at −25 °C show clear gas loss affecting the precision and mean level of the δO2/N2 record. Two different gas loss corrections are proposed to account for this effect, without altering the spectral properties of the original datasets. Although processes at play remain to be fully understood, previous studies have proposed a link between surface insolation, ice grain properties at close-off and δO2/N2 in air bubbles, from which an orbitally tuned chronologies of the Vostok and Dome Fuji ice core records have been derived over the last four climatic cycles. Here, we show that limitations caused by data quality and resolution, data filtering and uncertainties in the orbital tuning target limit the precision of this tuning method for EDC to at least 2.5 kyrs (thousands of years). Moreover, our extended record includes two periods of low eccentricity. During these intervals (around 400 ka and 750 ka), the matching between δO2/N2 and the different insolation curves is ambiguous because some local insolation maxima cannot be identified in the δO2/N2 record (and vice versa). Recognizing these limitations, we restrict the use of our δO2/N2 record to show that the EDC3 age scale is generally correct within its published uncertainty (6 kyrs) over the 300–800 ka period. We illustrate the uncertainties associated with data quality, filtering and tuning target for periods of low eccentricity by highlighting the difficulty to constrain the duration of Marine Isotopic Stage 11 based on the EDC δO2/N2 information.

scholarly journals A review of the brittle ice zone in polar ice cores

2014 ◽  
Vol 55 (68) ◽  
pp. 72-82 ◽  
Author(s):  
Peter D. Neff
Keyword(s):  
Atmospheric Pressure ◽  
Accumulation Rate ◽  
Ice Core ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Air Bubbles ◽  
Polar Ice ◽  
Overburden Pressure ◽  
Trapped Air ◽  
Borehole Temperatures

AbstractMaintaining ice-core quality through the brittle ice zone (BIZ) remains challenging for polar ice-core studies. At depth, increasing ice overburden pressurizes trapped air bubbles, causing fracture of cores upon exposure to atmospheric pressure. Fractured ice cores degrade analyses, reducing resolution and causing contamination. BIZ encounters at 18 sites across the Greenland, West and East Antarctic ice sheets are documented. The BIZ begins at a mean depth of 545 ± 162 m (1 standard deviation), extending to depths where ductile clathrate ice is reached: an average of 1132 ± 178 m depth. Ice ages in this zone vary with snow accumulation rate and ice thickness, beginning as young as 2 ka BP at Dye-3, Greenland, affecting ice >160 ka BP in age at Taylor Dome, Antarctica, and compromising up to 90% of retrieved samples at intermediate-depth sites. Effects of pressure and temperature on the BIZ are explored using modeled firn-column overburden pressure and borehole temperatures, revealing complex associations between firn densification and BIZ depth, and qualitatively supporting expected thinning of the BIZ at low ice temperatures due to shallower clathrate stability. Mitigating techniques for drilling, transport, sampling and analysis of brittle ice cores are also discussed.

scholarly journals Simulated features of the air-hydrate formation process in the Antarctic ice sheet at Vostok

1999 ◽  
Vol 29 ◽  
pp. 191-201 ◽  
Author(s):  
Andrey N. Salamatin ◽  
Vladimir Ya. Lipenkov ◽  
Takeo Hondoh ◽  
Tomoko Ikeda
Keyword(s):  
Ice Core ◽  
Hydrate Formation ◽  
Ice Cores ◽  
Air Bubbles ◽  
Air Bubble ◽  
Self Diffusion ◽  
Rate Limiting Step ◽  
Typical Time ◽  
Polar Ice Sheets ◽  
Selective Diffusion

AbstractA recently developed theory of post-nucleation conversion of an air bubble to air-hydrate crystal in ice is applied to simulate two different types of air-hydrate formation in polar ice sheets. The work is focused on interpretation of the Vostok (Antarctica) ice-core data. The hydrostatic compression of bubbles is the rate-limiting step of the phase transformation which is additionally influenced by selective diffusion of the gas components from neighboring air bubbles. The latter process leads to the gas fractionation resulting in lower (higher) N2/O2 ratios in air hydrates (coexisting bubbles) with respect to atmospheric air. The typical time of the post-nucleation conversion decreases at Vostok from 1300-200 a at the beginning to 50-3 a at the end of the transition zone. The model of the diffusive transport of the air constituents from air bubbles to hydrate crystals is constrained by the data of Raman spectra measurements. The oxygen and nitrogen self-diffusion (permeation) coefficients in ice are determined at 220 K as 4.5 × 10−8 and 9.5 × 10−8 mm2 a−1, respectively while the activation energy is estimated to be about 50 kJ mol−1. The gas-fractionation time-scale at Vostok, τF ∼300 a, appears to be two orders of magnitude less than the typical time of the air-hydrate nucleation, τz ∼30-35 ka, and thus the condition for the extreme gas fractionation, τF ≪ τz is satisfied. Application of the theory to the GRIP and GISP2 ice cores shows that on average, a significant gas fractionation cannot be expected for air hydrates in central Greenland. However, a noticeable (statistically valid) nitrogen enrichment might be observed in the last air bubbles at the end of the transition.

On the potential of coupling air content and O2/N2 from trapped air for establishing an ice core chronology tuned on local insolation

2011 ◽  
Vol 30 (23-24) ◽  
pp. 3280-3289 ◽  
Author(s):  
V.Ya. Lipenkov ◽  
D. Raynaud ◽  
M.F. Loutre ◽  
P. Duval
Keyword(s):  
Ice Core ◽  
Air Content ◽  
Trapped Air

scholarly journals Crystal growth rates in polar firn

1993 ◽  
Vol 18 ◽  
pp. 208-210
Author(s):  
Hitoshi Shoji ◽  
Atau Mitani ◽  
Kohji Horita ◽  
Chester C. Langway
Keyword(s):  
Growth Rate ◽  
Plastic Deformation ◽  
Crystal Growth ◽  
Growth Rates ◽  
Strain Field ◽  
Crystal Size ◽  
Ice Core ◽  
Transformation Process ◽  
Ice Crystals ◽  
Air Bubbles

Continuous crystal-size measurements made on the G6 Antarctic ice core (100m deep) show enhanced growth rates above a depth of 30 m (Zone 1) and in the interval between 70 and 80 m (Zone 2). Crystal growth in Zone 1 most probably takes place by a process of sublimation and condensation. The higher growth rate in Zone 2 is most probably related to the pore close-off transformation process in which a non-uniform strain field is created to form air bubbles by plastic deformation and “cannibalization” of individual ice crystals.

Leveling Device for Forming X-Ray Specimen

1980 ◽  
Vol 24 ◽  
pp. 369-370
Author(s):  
Vann Y. Won
Keyword(s):  
Air Bubbles ◽  
Plastic Film ◽  
X Ray ◽  
Trapped Air ◽  
Specimen Holder ◽  
Specimen Material ◽  
Accurate Definition ◽  
Analysis Window ◽  
Definition Of ◽  
Open Face

A device was made for preparing accurate definition of surface, depth and volume of liquid x-ray fluorescence specimens.The apparatus used in conjunction with a specimen holder and plastic film window material accurately and consistently forms a flat bobble-free analysis window on the open face of the specimen holder. The specimen holder in the form of a shallow cylinderical cup is slightly over filled and covered by the plastic film. Placement of the mating leveling apparatus over the film squeezes out trapped air bubbles, levels the exposed face of the specimen, draws the plastic film tightly over the exposed face of the specimen and allows easy installation of a film retaining O-ring to maintain the specimen material in a level state within the holder.

scholarly journals Tracer transport in an isochronal ice-sheet model

2016 ◽  
Vol 63 (237) ◽  
pp. 22-38 ◽  
Author(s):  
ANDREAS BORN
Keyword(s):  
Ice Core ◽  
Ice Sheet ◽  
Vertical Motion ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Model Parameters ◽  
Tracer Transport ◽  
Geochemical Tracers ◽  
Tuning Method ◽  
Polar Ice Sheets

ABSTRACTThe full history of ice sheet and climate interactions is recorded in the vertical profiles of geochemical tracers in polar ice sheets. Numerical simulations of these archives promise great advances both in the interpretation of these reconstructions and the validation of the models themselves. However, fundamental mathematical shortcomings of existing models subject tracers to spurious diffusion, thwarting straightforward solutions. Here, I propose a new vertical discretization for ice-sheet models that eliminates numerical diffusion entirely. Vertical motion through the model mesh is avoided by mimicking the real-world flow of ice as a thinning of underlying layers. A new layer is added to the surface at equidistant time intervals, isochronally, thus identifying each layer uniquely by its time of deposition and age. This new approach is implemented for a two-dimensional section through the summit of the Greenland ice sheet. The ability to directly compare simulations of vertical ice cores with reconstructed data is used to find optimal model parameters from a large ensemble of simulations. It is shown that because this tuning method uses information from all times included in the ice core, it constrains ice-sheet sensitivity more robustly than a realistic reproduction of the modern ice-sheet surface.

Why do we build the wall?

2019 ◽  
Vol 28 (1) ◽  
pp. 37-38 ◽  
Author(s):  
Ezequiel A Di Paolo
Keyword(s):  
Air Bubbles ◽  
Trapped Air ◽  
Good Move ◽  
Autopoietic Theory

I discuss the notion of bodies proposed by Villalobos and Razeto-Barry. I consider it a good move in a direction away from overly formal aspects of autopoietic theory, but in need of refinement. I suggest that because organismic boundaries are dialectical processes and not immanent walls, some autopoietic bodies can extend by incorporating parts of their environment as in the case of insects that use trapped air bubbles to breathe underwater.

scholarly journals Characteristics of air bubbles and hydrates in the Dome Fuji ice core, Antarctica

1999 ◽  
Vol 29 ◽  
pp. 207-210 ◽  
Author(s):  
Hideki Narita ◽  
Nobuhiko Azuma ◽  
Takeo Hondoh ◽  
Michiko Fujii ◽  
Mituo Kawaguchi ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Ice Core ◽  
Air Bubbles ◽  
Depth Range ◽  
Last Interglacial ◽  
Last Glacial ◽  
Maximum Period ◽  
Glacial Periods ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractAir bubbles trapped near the surface of an ice sheet are transformed into air hydrates below a certain depth Their volume and number varies partly with environment and climate. Air bubbles and hydrates at 120-2200 m depth in the Dome Fuji (Dome F) ice core were examined with a microscope. This depth range covers the Holocene/Last Glacial/Last Interglacial/Previous Glacial periods. No air bubbles were seen below about 1100 m depth, and air hydrates began to appear from about 600 m. The observed number of air bubbles and hydrates was similar to that found in the Vostok ice core. For the ice covering the Last Glacial Maximum period, however the hydrate concentration in the Dome F core is about half that of the Vostok core. Reference to snow metamorphism and packing does not explain this finding.

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