Post-coring entrapment of modern air in polar ice: Evidence from CFC-12 measurements in Antarctic firn air and shallow ice cores
This study is a comparison of CFC-12 (CCl2F2) measurements in firn air and ice core samples from three Antarctic sites: South Pole, West Antarctic Ice Sheet Divide (79.46°S, 112.13°W), and Siple Dome (81.65°S, 148.81°W). CFC-12 is a synthetic chlorofluorocarbon manufactured during the mid-late 20th...
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ftcdlib:oai:escholarship.org/ark:/13030/qt82f9b99c 2023-05-15T13:38:01+02:00 Post-coring entrapment of modern air in polar ice: Evidence from CFC-12 measurements in Antarctic firn air and shallow ice cores Saltzman, ES Aydin, KM Montzka, SA Battle, MO Williams, MB De Bruyn, WJ Butler, JH Verhulst, KR Tatum, C Gun, BK Plotkin, DA Hall, BD 2009-01-01 application/pdf https://escholarship.org/uc/item/82f9b99c unknown eScholarship, University of California qt82f9b99c https://escholarship.org/uc/item/82f9b99c CC-BY CC-BY article 2009 ftcdlib 2020-01-24T23:53:08Z This study is a comparison of CFC-12 (CCl2F2) measurements in firn air and ice core samples from three Antarctic sites: South Pole, West Antarctic Ice Sheet Divide (79.46°S, 112.13°W), and Siple Dome (81.65°S, 148.81°W). CFC-12 is a synthetic chlorofluorocarbon manufactured during the mid-late 20th century for use as a refrigerant and an aerosol spray propellant. Its atmospheric history is well established with agreement among instrumental time series measurements and industry-reported production data [Walker et al., 2000], the distribution of dissolved CFC-12 in the oceans [e.g. Weiss et al., 1985], and firn air measurements [Butler et al., 1999]. The atmospheric history indicates that there was no measureable CFC-12 in the atmosphere prior to the 1940’s. The firn air CFC-12 profiles are consistent with the known atmospheric history of this gas. In contrast, the air in ice core samples collected near the close-off depth exhibit anomalously high CFC-12 levels. We propose that this is due to entrapment of modern air in open pores that close after drilling, resulting in elevated CFC-12 mixing ratios. These results demonstrate how the composition of air trapped in shallow ice cores can be altered during the post-drilling period through purely physical processes. Comparison of firn air and ice core bubble composition is one of the commonly used tools for studying the bubble close-off process. The post-drilling entrapment process detected in this study represents a potential complication for such investigations. Article in Journal/Newspaper Antarc* Antarctic ice core Ice Sheet South pole South pole University of California: eScholarship Antarctic Siple ENVELOPE(-83.917,-83.917,-75.917,-75.917) Siple Dome ENVELOPE(-148.833,-148.833,-81.667,-81.667) South Pole West Antarctic Ice Sheet |
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Open Polar |
collection |
University of California: eScholarship |
op_collection_id |
ftcdlib |
language |
unknown |
description |
This study is a comparison of CFC-12 (CCl2F2) measurements in firn air and ice core samples from three Antarctic sites: South Pole, West Antarctic Ice Sheet Divide (79.46°S, 112.13°W), and Siple Dome (81.65°S, 148.81°W). CFC-12 is a synthetic chlorofluorocarbon manufactured during the mid-late 20th century for use as a refrigerant and an aerosol spray propellant. Its atmospheric history is well established with agreement among instrumental time series measurements and industry-reported production data [Walker et al., 2000], the distribution of dissolved CFC-12 in the oceans [e.g. Weiss et al., 1985], and firn air measurements [Butler et al., 1999]. The atmospheric history indicates that there was no measureable CFC-12 in the atmosphere prior to the 1940’s. The firn air CFC-12 profiles are consistent with the known atmospheric history of this gas. In contrast, the air in ice core samples collected near the close-off depth exhibit anomalously high CFC-12 levels. We propose that this is due to entrapment of modern air in open pores that close after drilling, resulting in elevated CFC-12 mixing ratios. These results demonstrate how the composition of air trapped in shallow ice cores can be altered during the post-drilling period through purely physical processes. Comparison of firn air and ice core bubble composition is one of the commonly used tools for studying the bubble close-off process. The post-drilling entrapment process detected in this study represents a potential complication for such investigations. |
format |
Article in Journal/Newspaper |
author |
Saltzman, ES Aydin, KM Montzka, SA Battle, MO Williams, MB De Bruyn, WJ Butler, JH Verhulst, KR Tatum, C Gun, BK Plotkin, DA Hall, BD |
spellingShingle |
Saltzman, ES Aydin, KM Montzka, SA Battle, MO Williams, MB De Bruyn, WJ Butler, JH Verhulst, KR Tatum, C Gun, BK Plotkin, DA Hall, BD Post-coring entrapment of modern air in polar ice: Evidence from CFC-12 measurements in Antarctic firn air and shallow ice cores |
author_facet |
Saltzman, ES Aydin, KM Montzka, SA Battle, MO Williams, MB De Bruyn, WJ Butler, JH Verhulst, KR Tatum, C Gun, BK Plotkin, DA Hall, BD |
author_sort |
Saltzman, ES |
title |
Post-coring entrapment of modern air in polar ice: Evidence from CFC-12 measurements in Antarctic firn air and shallow ice cores |
title_short |
Post-coring entrapment of modern air in polar ice: Evidence from CFC-12 measurements in Antarctic firn air and shallow ice cores |
title_full |
Post-coring entrapment of modern air in polar ice: Evidence from CFC-12 measurements in Antarctic firn air and shallow ice cores |
title_fullStr |
Post-coring entrapment of modern air in polar ice: Evidence from CFC-12 measurements in Antarctic firn air and shallow ice cores |
title_full_unstemmed |
Post-coring entrapment of modern air in polar ice: Evidence from CFC-12 measurements in Antarctic firn air and shallow ice cores |
title_sort |
post-coring entrapment of modern air in polar ice: evidence from cfc-12 measurements in antarctic firn air and shallow ice cores |
publisher |
eScholarship, University of California |
publishDate |
2009 |
url |
https://escholarship.org/uc/item/82f9b99c |
long_lat |
ENVELOPE(-83.917,-83.917,-75.917,-75.917) ENVELOPE(-148.833,-148.833,-81.667,-81.667) |
geographic |
Antarctic Siple Siple Dome South Pole West Antarctic Ice Sheet |
geographic_facet |
Antarctic Siple Siple Dome South Pole West Antarctic Ice Sheet |
genre |
Antarc* Antarctic ice core Ice Sheet South pole South pole |
genre_facet |
Antarc* Antarctic ice core Ice Sheet South pole South pole |
op_relation |
qt82f9b99c https://escholarship.org/uc/item/82f9b99c |
op_rights |
CC-BY |
op_rightsnorm |
CC-BY |
_version_ |
1766100577939357696 |