Analytical constraints on layered gas trapping and smoothing of atmospheric variability in ice under low-accumulation conditions
We investigate for the first time the loss and alteration of past atmospheric information from air trapping mechanisms under low-accumulation conditions through continuous CH 4 (and CO) measurements. Methane concentration changes were measured over the Dansgaard–Oeschger event 17 (DO-17, ∼ 60 000 yr...
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ftdoajarticles:oai:doaj.org/article:cc224fb10ce1456a8d558f2499f6589a 2023-05-15T13:57:41+02:00 Analytical constraints on layered gas trapping and smoothing of atmospheric variability in ice under low-accumulation conditions K. Fourteau X. Faïn P. Martinerie A. Landais A. A. Ekaykin V. Ya. Lipenkov J. Chappellaz 2017-12-01T00:00:00Z https://doi.org/10.5194/cp-13-1815-2017 https://doaj.org/article/cc224fb10ce1456a8d558f2499f6589a EN eng Copernicus Publications https://www.clim-past.net/13/1815/2017/cp-13-1815-2017.pdf https://doaj.org/toc/1814-9324 https://doaj.org/toc/1814-9332 doi:10.5194/cp-13-1815-2017 1814-9324 1814-9332 https://doaj.org/article/cc224fb10ce1456a8d558f2499f6589a Climate of the Past, Vol 13, Pp 1815-1830 (2017) Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 article 2017 ftdoajarticles https://doi.org/10.5194/cp-13-1815-2017 2022-12-30T21:47:08Z We investigate for the first time the loss and alteration of past atmospheric information from air trapping mechanisms under low-accumulation conditions through continuous CH 4 (and CO) measurements. Methane concentration changes were measured over the Dansgaard–Oeschger event 17 (DO-17, ∼ 60 000 yr BP) in the Antarctic Vostok 4G-2 ice core. Measurements were performed using continuous-flow analysis combined with laser spectroscopy. The results highlight many anomalous layers at the centimeter scale that are unevenly distributed along the ice core. The anomalous methane mixing ratios differ from those in the immediate surrounding layers by up to 50 ppbv. This phenomenon can be theoretically reproduced by a simple layered trapping model, creating very localized gas age scale inversions. We propose a method for cleaning the record of anomalous values that aims at minimizing the bias in the overall signal. Once the layered-trapping-induced anomalies are removed from the record, DO-17 appears to be smoother than its equivalent record from the high-accumulation WAIS Divide ice core. This is expected due to the slower sinking and densification speeds of firn layers at lower accumulation. However, the degree of smoothing appears surprisingly similar between modern and DO-17 conditions at Vostok. This suggests that glacial records of trace gases from low-accumulation sites in the East Antarctic plateau can provide a better time resolution of past atmospheric composition changes than previously expected. We also developed a numerical method to extract the gas age distributions in ice layers after the removal of the anomalous layers based on comparison with a weakly smoothed record. It is particularly adapted for the conditions of the East Antarctic plateau, as it helps to characterize smoothing for a large range of very low-temperature and low-accumulation conditions. Article in Journal/Newspaper Antarc* Antarctic ice core Directory of Open Access Journals: DOAJ Articles Antarctic The Antarctic Climate of the Past 13 12 1815 1830 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 |
spellingShingle |
Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 K. Fourteau X. Faïn P. Martinerie A. Landais A. A. Ekaykin V. Ya. Lipenkov J. Chappellaz Analytical constraints on layered gas trapping and smoothing of atmospheric variability in ice under low-accumulation conditions |
topic_facet |
Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 |
description |
We investigate for the first time the loss and alteration of past atmospheric information from air trapping mechanisms under low-accumulation conditions through continuous CH 4 (and CO) measurements. Methane concentration changes were measured over the Dansgaard–Oeschger event 17 (DO-17, ∼ 60 000 yr BP) in the Antarctic Vostok 4G-2 ice core. Measurements were performed using continuous-flow analysis combined with laser spectroscopy. The results highlight many anomalous layers at the centimeter scale that are unevenly distributed along the ice core. The anomalous methane mixing ratios differ from those in the immediate surrounding layers by up to 50 ppbv. This phenomenon can be theoretically reproduced by a simple layered trapping model, creating very localized gas age scale inversions. We propose a method for cleaning the record of anomalous values that aims at minimizing the bias in the overall signal. Once the layered-trapping-induced anomalies are removed from the record, DO-17 appears to be smoother than its equivalent record from the high-accumulation WAIS Divide ice core. This is expected due to the slower sinking and densification speeds of firn layers at lower accumulation. However, the degree of smoothing appears surprisingly similar between modern and DO-17 conditions at Vostok. This suggests that glacial records of trace gases from low-accumulation sites in the East Antarctic plateau can provide a better time resolution of past atmospheric composition changes than previously expected. We also developed a numerical method to extract the gas age distributions in ice layers after the removal of the anomalous layers based on comparison with a weakly smoothed record. It is particularly adapted for the conditions of the East Antarctic plateau, as it helps to characterize smoothing for a large range of very low-temperature and low-accumulation conditions. |
format |
Article in Journal/Newspaper |
author |
K. Fourteau X. Faïn P. Martinerie A. Landais A. A. Ekaykin V. Ya. Lipenkov J. Chappellaz |
author_facet |
K. Fourteau X. Faïn P. Martinerie A. Landais A. A. Ekaykin V. Ya. Lipenkov J. Chappellaz |
author_sort |
K. Fourteau |
title |
Analytical constraints on layered gas trapping and smoothing of atmospheric variability in ice under low-accumulation conditions |
title_short |
Analytical constraints on layered gas trapping and smoothing of atmospheric variability in ice under low-accumulation conditions |
title_full |
Analytical constraints on layered gas trapping and smoothing of atmospheric variability in ice under low-accumulation conditions |
title_fullStr |
Analytical constraints on layered gas trapping and smoothing of atmospheric variability in ice under low-accumulation conditions |
title_full_unstemmed |
Analytical constraints on layered gas trapping and smoothing of atmospheric variability in ice under low-accumulation conditions |
title_sort |
analytical constraints on layered gas trapping and smoothing of atmospheric variability in ice under low-accumulation conditions |
publisher |
Copernicus Publications |
publishDate |
2017 |
url |
https://doi.org/10.5194/cp-13-1815-2017 https://doaj.org/article/cc224fb10ce1456a8d558f2499f6589a |
geographic |
Antarctic The Antarctic |
geographic_facet |
Antarctic The Antarctic |
genre |
Antarc* Antarctic ice core |
genre_facet |
Antarc* Antarctic ice core |
op_source |
Climate of the Past, Vol 13, Pp 1815-1830 (2017) |
op_relation |
https://www.clim-past.net/13/1815/2017/cp-13-1815-2017.pdf https://doaj.org/toc/1814-9324 https://doaj.org/toc/1814-9332 doi:10.5194/cp-13-1815-2017 1814-9324 1814-9332 https://doaj.org/article/cc224fb10ce1456a8d558f2499f6589a |
op_doi |
https://doi.org/10.5194/cp-13-1815-2017 |
container_title |
Climate of the Past |
container_volume |
13 |
container_issue |
12 |
container_start_page |
1815 |
op_container_end_page |
1830 |
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1766265495091150848 |