Local artifacts in ice core methane records caused by layered bubble trapping and in situ production: a multi-site investigation
Advances in trace gas analysis allow localised, non-atmospheric features to be resolved in ice cores, superimposed on the coherent atmospheric signal. These high-frequency signals could not have survived the low-pass filter effect that gas diffusion in the firn exerts on the atmospheric history and...
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Language: | English |
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European Geosciences Union
2016
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Online Access: | https://nrl.northumbria.ac.uk/id/eprint/37624/ https://doi.org/10.5194/cp-12-1061-2016 https://nrl.northumbria.ac.uk/id/eprint/37624/1/Rhodes%20et%20al%20-%20Local%20artifacts%20in%20ice%20core%20methane%20records%20OA.pdf |
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ftunivnorthumb:oai:nrl.northumbria.ac.uk:37624 2023-05-15T16:28:44+02:00 Local artifacts in ice core methane records caused by layered bubble trapping and in situ production: a multi-site investigation Rhodes, Rachael H. Faïn, Xavier Brook, Edward J. McConnell, Joseph R. Maselli, Olivia J. Sigl, Michael Edwards, Jon Buizert, Christo Blunier, Thomas Chappellaz, Jérôme Freitag, Johannes 2016-04-26 text https://nrl.northumbria.ac.uk/id/eprint/37624/ https://doi.org/10.5194/cp-12-1061-2016 https://nrl.northumbria.ac.uk/id/eprint/37624/1/Rhodes%20et%20al%20-%20Local%20artifacts%20in%20ice%20core%20methane%20records%20OA.pdf en eng European Geosciences Union https://nrl.northumbria.ac.uk/id/eprint/37624/1/Rhodes%20et%20al%20-%20Local%20artifacts%20in%20ice%20core%20methane%20records%20OA.pdf Rhodes, Rachael H., Faïn, Xavier, Brook, Edward J., McConnell, Joseph R., Maselli, Olivia J., Sigl, Michael, Edwards, Jon, Buizert, Christo, Blunier, Thomas, Chappellaz, Jérôme and Freitag, Johannes (2016) Local artifacts in ice core methane records caused by layered bubble trapping and in situ production: a multi-site investigation. Climate of the Past, 12 (4). pp. 1061-1077. ISSN 1814-9332 cc_by CC-BY F800 Physical and Terrestrial Geographical and Environmental Sciences Article PeerReviewed 2016 ftunivnorthumb https://doi.org/10.5194/cp-12-1061-2016 2022-09-25T06:08:59Z Advances in trace gas analysis allow localised, non-atmospheric features to be resolved in ice cores, superimposed on the coherent atmospheric signal. These high-frequency signals could not have survived the low-pass filter effect that gas diffusion in the firn exerts on the atmospheric history and therefore do not result from changes in the atmospheric composition at the ice sheet surface. Using continuous methane (CH4) records obtained from five polar ice cores, we characterise these non-atmospheric signals and explore their origin. Isolated samples, enriched in CH4 in the Tunu13 (Greenland) record are linked to the presence of melt layers. Melting can enrich the methane concentration due to a solubility effect, but we find that an additional in situ process is required to generate the full magnitude of these anomalies. Furthermore, in all the ice cores studied there is evidence of reproducible, decimetre-scale CH4 variability. Through a series of tests, we demonstrate that this is an artifact of layered bubble trapping in a heterogeneous-density firn column; we use the term “trapping signal” for this phenomenon. The peak-to-peak amplitude of the trapping signal is typically 5ppb, but may exceed 40ppb. Signal magnitude increases with atmospheric CH4 growth rate and seasonal density contrast, and decreases with accumulation rate. Significant annual periodicity is present in the CH4 variability of two Greenland ice cores, suggesting that layered gas trapping at these sites is controlled by regular, seasonal variations in the physical properties of the firn. Future analytical campaigns should anticipate high-frequency artifacts at high-melt ice core sites or during time periods with high atmospheric CH4 growth rate in order to avoid misinterpretation of such features as past changes in atmospheric composition. Article in Journal/Newspaper Greenland Greenland ice cores ice core Ice Sheet Northumbria University, Newcastle: Northumbria Research Link (NRL) Greenland Climate of the Past 12 4 1061 1077 |
institution |
Open Polar |
collection |
Northumbria University, Newcastle: Northumbria Research Link (NRL) |
op_collection_id |
ftunivnorthumb |
language |
English |
topic |
F800 Physical and Terrestrial Geographical and Environmental Sciences |
spellingShingle |
F800 Physical and Terrestrial Geographical and Environmental Sciences Rhodes, Rachael H. Faïn, Xavier Brook, Edward J. McConnell, Joseph R. Maselli, Olivia J. Sigl, Michael Edwards, Jon Buizert, Christo Blunier, Thomas Chappellaz, Jérôme Freitag, Johannes Local artifacts in ice core methane records caused by layered bubble trapping and in situ production: a multi-site investigation |
topic_facet |
F800 Physical and Terrestrial Geographical and Environmental Sciences |
description |
Advances in trace gas analysis allow localised, non-atmospheric features to be resolved in ice cores, superimposed on the coherent atmospheric signal. These high-frequency signals could not have survived the low-pass filter effect that gas diffusion in the firn exerts on the atmospheric history and therefore do not result from changes in the atmospheric composition at the ice sheet surface. Using continuous methane (CH4) records obtained from five polar ice cores, we characterise these non-atmospheric signals and explore their origin. Isolated samples, enriched in CH4 in the Tunu13 (Greenland) record are linked to the presence of melt layers. Melting can enrich the methane concentration due to a solubility effect, but we find that an additional in situ process is required to generate the full magnitude of these anomalies. Furthermore, in all the ice cores studied there is evidence of reproducible, decimetre-scale CH4 variability. Through a series of tests, we demonstrate that this is an artifact of layered bubble trapping in a heterogeneous-density firn column; we use the term “trapping signal” for this phenomenon. The peak-to-peak amplitude of the trapping signal is typically 5ppb, but may exceed 40ppb. Signal magnitude increases with atmospheric CH4 growth rate and seasonal density contrast, and decreases with accumulation rate. Significant annual periodicity is present in the CH4 variability of two Greenland ice cores, suggesting that layered gas trapping at these sites is controlled by regular, seasonal variations in the physical properties of the firn. Future analytical campaigns should anticipate high-frequency artifacts at high-melt ice core sites or during time periods with high atmospheric CH4 growth rate in order to avoid misinterpretation of such features as past changes in atmospheric composition. |
format |
Article in Journal/Newspaper |
author |
Rhodes, Rachael H. Faïn, Xavier Brook, Edward J. McConnell, Joseph R. Maselli, Olivia J. Sigl, Michael Edwards, Jon Buizert, Christo Blunier, Thomas Chappellaz, Jérôme Freitag, Johannes |
author_facet |
Rhodes, Rachael H. Faïn, Xavier Brook, Edward J. McConnell, Joseph R. Maselli, Olivia J. Sigl, Michael Edwards, Jon Buizert, Christo Blunier, Thomas Chappellaz, Jérôme Freitag, Johannes |
author_sort |
Rhodes, Rachael H. |
title |
Local artifacts in ice core methane records caused by layered bubble trapping and in situ production: a multi-site investigation |
title_short |
Local artifacts in ice core methane records caused by layered bubble trapping and in situ production: a multi-site investigation |
title_full |
Local artifacts in ice core methane records caused by layered bubble trapping and in situ production: a multi-site investigation |
title_fullStr |
Local artifacts in ice core methane records caused by layered bubble trapping and in situ production: a multi-site investigation |
title_full_unstemmed |
Local artifacts in ice core methane records caused by layered bubble trapping and in situ production: a multi-site investigation |
title_sort |
local artifacts in ice core methane records caused by layered bubble trapping and in situ production: a multi-site investigation |
publisher |
European Geosciences Union |
publishDate |
2016 |
url |
https://nrl.northumbria.ac.uk/id/eprint/37624/ https://doi.org/10.5194/cp-12-1061-2016 https://nrl.northumbria.ac.uk/id/eprint/37624/1/Rhodes%20et%20al%20-%20Local%20artifacts%20in%20ice%20core%20methane%20records%20OA.pdf |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland Greenland ice cores ice core Ice Sheet |
genre_facet |
Greenland Greenland ice cores ice core Ice Sheet |
op_relation |
https://nrl.northumbria.ac.uk/id/eprint/37624/1/Rhodes%20et%20al%20-%20Local%20artifacts%20in%20ice%20core%20methane%20records%20OA.pdf Rhodes, Rachael H., Faïn, Xavier, Brook, Edward J., McConnell, Joseph R., Maselli, Olivia J., Sigl, Michael, Edwards, Jon, Buizert, Christo, Blunier, Thomas, Chappellaz, Jérôme and Freitag, Johannes (2016) Local artifacts in ice core methane records caused by layered bubble trapping and in situ production: a multi-site investigation. Climate of the Past, 12 (4). pp. 1061-1077. ISSN 1814-9332 |
op_rights |
cc_by |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.5194/cp-12-1061-2016 |
container_title |
Climate of the Past |
container_volume |
12 |
container_issue |
4 |
container_start_page |
1061 |
op_container_end_page |
1077 |
_version_ |
1766018405592203264 |