Atmospheric Trace-Gas Variations as Revealed by Air Trapped in an Ice Core from Law Dome, Antarctica

Etheridge, D. M.; Pearman, G. I.; Silva, F. de

doi:10.1017/s0260305500004110

Cited by 81 publications

(10 citation statements)

References 15 publications

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“…The air is liberated from the ice core samples using a dry‐extraction technique, in which ice is mechanically shredded under vacuum [ Etheridge et al , 1988; Sowers and Jubenville , 2000]. The extraction chamber is a cylindrical electropolished stainless steel tube, which is 14.5 cm in diameter and 20 cm in length.…”

Section: Methodsmentioning

confidence: 99%

Feasibility of reconstructing paleoatmospheric records of selected alkanes, methyl halides, and sulfur gases from Greenland ice cores

2007

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Seven short‐lived atmospheric trace gases were measured in 25 ice core samples from Summit, Greenland. Samples were selected from contemporaneous sections of fluid‐ and dry‐drilled ice cores to examine what effects using n‐butyl acetate as the drill fluid would have on the measurements. The gases include three light alkanes, C2H6, C3H6, and n‐C4H10; two methyl halides, CH3Cl and CH3Br; and two sulfur compounds, OCS and CS2, with gas ages from 125 to 325 years before present. Alkane levels are comparable to measurements in modern Arctic air, although C2H6 exhibits greater variability than expected compared with C3H6 and n‐C4H10. These results are not consistent with the idea that the alkanes are primarily of anthropogenic origin, suggesting that the ice cores may not truly record a paleoatmospheric signal with respect to these gases. The CH3Br results are consistent with previous observations of “excess” CH3Br in Greenland firn air. In situ production processes appear to overwhelm the paleoatmospheric signal of this gas. CH3Cl exhibits the same effect to a lesser extent. OCS levels are similar to those in Antarctic ice cores and appear to reflect paleoatmospheric levels. CS2 results are similar to the limited database of modern atmospheric measurements. Only C3H8 and n‐C4H10 exhibit clear evidence of contamination because of the presence of the drill fluid. The results indicate that it is possible to analyze many trace gases in fluid‐ and dry‐drilled ice samples. However, it appears that in situ production may significantly alter the levels of some trace gases in Greenland ice cores.

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Section: Methodsmentioning

confidence: 99%

Feasibility of reconstructing paleoatmospheric records of selected alkanes, methyl halides, and sulfur gases from Greenland ice cores

2007

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“…The ground temperature changes inferred by this study appear to be correlated with the atmospheric COP concentration . Measurements of methane concentration in an antarctic ice core follow the carbon dioxide trends (Etheridge et al, 1988). The timing of the temperature minimum during the Little Ice Age (c. 1800 AD) coincides with the increase in the concentration of atmospheric COz (c. 1810 AD).…”

Section: Discussionmentioning

confidence: 69%

Ground temperature changes in eastern Canada: borehole temperature evidence compared with proxy data

Beltrami

Mareschal

1993

Terra Nova

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Borehole temperature logs have been inverted to infer ground temperature histories (GTH) in eastern and central Canada. Regional ground temperature histories were obtained by simultaneous inversion of several temperature profiles from the same areas. Simultaneous inversion of 21 temperature logs sampled across all of eastern and central Canada yielded an average solution for this region. All but three of the studied sites show signs of warming in the last 150 years. This period of warming, which started after 1800 AD, was found throughout this part of Canada. The warming followed a cooler period corresponding to the little Ice Age. The inferred ground temperature histories exhibit long-term trends similar to those obtained from treering growth indices in nearby regions and stable isotope data in the southern hemisphere. The modern warming appears correlated with the atmospheric concentration of CO2 as measured in ice cores.

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“…Air bubbles in polar glacier ice are formed by the densification process of firn into ice. Composition of air in ice is essentially the same as that of the atmosphere at the time of bubble formations; thus the analyses of air in ice allow us to investigate the past atmospheric conditions (Scholander and others, 1961; Matsuo and Miyake, 1966; Stauffer and Berner, 1978; Oeschger and others, 1982; Barnola and others, 1987; Etheridge and others, 1988).…”

Section: Introductionmentioning

confidence: 99%

Thinning of the Ice Sheet Estimated from Total Gas Content of Ice Cores in Mizuho Plateau, East Antarctica

et al. 1990

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A linear relation between total gas content in ice and the elevation of ice formation (i .e. pore close-off) was obtained from seven shallow ice cores in Mizuho Plateau, Antarctica. The derived relation was applied to the vertical profile of total gas content in a 700 m long ice core at Mizuho Station . A general trend of gradual increase in total gas content was observed from 600 to 200 m in depth, from which toward the upper layer it showed a steep increase. After eliminating the effect of down-slope flow of ice around Mizuho Station, it was estimated that the thickness of the ice sheet decreased by about 350 m at maximum during the last 2000 years. This tendency also appears in the S 18 0 profile of the same ice core.

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Atmospheric Trace-Gas Variations as Revealed by Air Trapped in an Ice Core from Law Dome, Antarctica

Cited by 81 publications

References 15 publications

Feasibility of reconstructing paleoatmospheric records of selected alkanes, methyl halides, and sulfur gases from Greenland ice cores

Feasibility of reconstructing paleoatmospheric records of selected alkanes, methyl halides, and sulfur gases from Greenland ice cores

Ground temperature changes in eastern Canada: borehole temperature evidence compared with proxy data

Thinning of the Ice Sheet Estimated from Total Gas Content of Ice Cores in Mizuho Plateau, East Antarctica

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