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

Abstract

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.

In-Situ Radiocarbon Production by Neutrons and Muons in an Antarctic Blue Ice Field at Scharffenbergbotnen: A Status Report

“…Table 1 shows details about the ice samples and depth, the gas yields, and the results of the 14 C analysis. The mean value of the air yields from the ice samples is 108 mL/kg, which is in agreement with values earlier obtained by van Roijen (1995). The CO 2 concentrations are close to modern values in the surface samples.…”

“…That would mean a retainment of 23% in-situ 14 C of the firn in the ice, which is different from the observation by van der Kemp et al (2000) who do not observe in situ production in accumulating ice. The 14 CO profiles obtained by van Roijen et al (1995) in shallow ice cores of 3 and 10 m from the same area are almost equal to the one obtained in the 52 m as is shown by the line through the data (Figure 2 above). This similarity indicates an equal extraction efficiency of 14 CO for the three cores.…”

“…The 14 CO profiles obtained by van Roijen et al (1995) in shallow ice cores of 3 and 10 m from the same area are almost equal to the one obtained in the 52 m as is shown by the line through the data (Figure 2 above). This similarity indicates an equal extraction efficiency of 14 CO for the three cores.…”

In situ cosmogenic radiocarbon production and 2‐D ice flow line modeling for an Antarctic blue ice area

“…Several previous studies have used 14 C concentrations in combination with equation (12) to estimate ablation rates in glaciers and BIAs [e.g., Lal et al , 1990; Van Roijen et al , 1995; Van der Borg et al , 2001]. Our modeling results show that neglecting the flow history of the ice parcels can result in an error of up to 25% where topography is rugged (black dashed line in Figure 7b); the proximity of many Antarctic BIAs to mountain ranges and nunataks [ Bintanja , 1999; Sinisalo and Moore , 2010] suggests that caution is warranted when estimating ablation rates from radiocarbon data.…”

“…The opposite is also true: where ablation rates are high, activity will be low. By this principle, measurements of 14 C have been used to estimate BIA ablation rates [e.g., Lal et al , 1990; Van Roijen et al , 1995; Van der Borg et al , 2001]. It has also been suggested that 14 C in ice core samples can be used to infer past changes in accumulation rate [ Lal et al , 1990, 2000].…”