Ages and ablation and accumulation rates from <sup>14</sup>C measurements on Antarctic ice

ABSTRACT. We use a dry extraction method to obtain trapped CO2 of shallow ice cores from a blue ice area of East Antarctica. In-situ-produced 14C extracted in 14C02 and 14C0 concentrations show a mean ratio of 3.4 ± 0.4. Correction for insitu 14C02 resulted in ice ages within 7-13 ka. The accumulation and ablation rates determined from the in-situ production of 7-20 cm yr-1 and 10-13 cm yr-1, respectively, agree with field measurements, and thus indicate close to total efficiency of extraction.

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“…Further details of the samples were reported elsewhere (van Roijen et al 1995). Table 1 shows the results of the 14C analysis.…”

Section: C Depth Profilesmentioning

confidence: 99%

“…To separate the in-situ 14C02 signal from the natural component, we follow the procedure described by van Roijen et al (1994). Thus, we fit the equation for in-situ production in ablating ice to the 14C0 data c(X) = cl exp (-x/A) + co…”

Section: C Depth Profilesmentioning

confidence: 99%

A Correction for In-Situ¹⁴C in Antarctic Ice with ¹⁴CO

Roijen¹,

Borg

Jong

et al. 1995

Radiocarbon

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“…Inorganic CO 2 eventually trapped in air bubbles below the firn-ice transition is a less suitable 14 Cdating target since it may contain a substantial contribution of in situ-produced 14 C (mainly via spallation of oxygen in the ice by energetic cosmic ray neutrons, Lal et al 1990;Lal et al 2000;Lal et al 2001;Van Roijen et al 1995). This is especially true for mountain drill sites, where the in situ contribution is enhanced due to high altitudes and low accumulation rates.…”

Section: Introductionmentioning

confidence: 99%

Radiocarbon Determination of Particulate Organic Carbon in Non-Temperated, Alpine Glacier Ice

Steier

Drosg²,

Fedi³

et al. 2006

Radiocarbon

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ABSTRACT. Dating ice samples from glaciers via radiocarbon is a challenge that requires systematic investigations. This work describes an approach for extraction and accelerator mass spectrometry (AMS) 14 C analysis of the particulate organic carbon (POC) fraction in glacier ice samples. Measurements were performed at VERA (Vienna Environmental Research Accelerator) on ice samples obtained mainly from the non-temperated ablation zone of the Grenzgletscher (Grenz Glacier) system (Monte Rosa Massif, Swiss Alps). The samples were obtained from 2 sampling sites situated roughly on a common flow line. The sample masses used were between 0.3 and 1.4 kg of ice, yielding between 18 and 307 µg of carbon as POC. The carbon contamination introduced during sample processing varied between 5.4 and 33 µg C and originated mainly from the quartz filters and the rinsing liquids used in processing. Minimum sample sizes for successful graphitization of CO 2 in our laboratory could be reduced to <10 µg carbon, with a background in the graphitization process of ~0.5 µg of 40-pMC carbon. Evaluation of the whole procedure via 11 Grenzgletscher samples revealed a surprisingly large scatter of pMC values. We obtain a mean calibrated age of 2100 BC to AD 900 (95.4% confidence level), which is not significantly different for the 2 sampling sites. Discussions of these results suggest that single 14 C dates of glacial POC are presently of limited significance. Future improvements with respect to analytical precision and sample characterization are proposed in order to fully explore the POC dating potential.

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