Towards reconstructing the Arctic atmospheric methane history over the 20th century: measurement and modelling results for the North Greenland Ice Core Project firn
<p>Systematic measurements of atmospheric methane (CH<span class="inline-formula"><sub>4</sub></span>) mole fractions at the northern high latitudes only began in the early 1980s. Although CH<span class="inline-formula"><sub>4</sub>...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2022-05-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/22/6899/2022/acp-22-6899-2022.pdf |
| _version_ | 1811324893347708928 |
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| author | T. Umezawa S. Sugawara K. Kawamura K. Kawamura K. Kawamura I. Oyabu S. J. Andrews S. J. Andrews T. Saito S. Aoki T. Nakazawa |
| author_facet | T. Umezawa S. Sugawara K. Kawamura K. Kawamura K. Kawamura I. Oyabu S. J. Andrews S. J. Andrews T. Saito S. Aoki T. Nakazawa |
| author_sort | T. Umezawa |
| collection | DOAJ |
| description | <p>Systematic measurements of atmospheric methane (CH<span class="inline-formula"><sub>4</sub></span>) mole fractions at the northern high latitudes only began in the early 1980s. Although CH<span class="inline-formula"><sub>4</sub></span> measurements from Greenland ice cores consistently covered the period before <span class="inline-formula">∼</span> 1900, no reliable observational record is available for the intermediate period. We newly report a data set of trace
gases from the air trapped in firn (an intermediate stage between snow and glacial ice formation) collected at the NGRIP (North Greenland Ice Core Project) site in 2001. We also use a set of published firn air data at the NEEM (North Greenland Eemian ice Drilling) site. The two Arctic firn air data sets are analysed with a firn air transport model, which translates
historical variations to depth profiles of trace gases in firn. We examine a variety of possible firn diffusivity profiles, using a suite of measured trace gases, and reconstruct the CH<span class="inline-formula"><sub>4</sub></span> mole fraction by an iterative dating method. Although the reconstructions of the Arctic CH<span class="inline-formula"><sub>4</sub></span> mole fraction before the mid-1970s still has large uncertainties (<span class="inline-formula">></span> 30 ppb – parts per billion), we find a relatively narrow range of atmospheric CH<span class="inline-formula"><sub>4</sub></span> history that is consistent with both depth profiles of NGRIP and NEEM. The atmospheric CH<span class="inline-formula"><sub>4</sub></span> history inferred by this study is more consistent with the atmospheric CH<span class="inline-formula"><sub>4</sub></span> scenario prepared for the NEEM firn modelling than that for the CMIP6 (Climate Model Intercomparison Project Phase 6) experiments. Our study shows that the atmospheric CH<span class="inline-formula"><sub>4</sub></span> scenario used for the NEEM firn modelling is considered to be the current best choice for the Arctic CH<span class="inline-formula"><sub>4</sub></span> history, but it should not be used to tune firn air transport models until being verified by further measurements from sources such as the Arctic ice cores. Given the current difficulty in reconstructing the CH<span class="inline-formula"><sub>4</sub></span> history with low uncertainty from the firn air data sets from Greenland, future sampling and measurements of ice cores at a high-accumulation site may be the only way to accurately reconstruct the atmospheric CH<span class="inline-formula"><sub>4</sub></span> trend over the 20th century.</p> |
| first_indexed | 2024-04-13T14:22:21Z |
| format | Article |
| id | doaj.art-e69dc28cc5cb4a14b86e13c706743803 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-04-13T14:22:21Z |
| publishDate | 2022-05-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-e69dc28cc5cb4a14b86e13c7067438032022-12-22T02:43:25ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242022-05-01226899691710.5194/acp-22-6899-2022Towards reconstructing the Arctic atmospheric methane history over the 20th century: measurement and modelling results for the North Greenland Ice Core Project firnT. Umezawa0S. Sugawara1K. Kawamura2K. Kawamura3K. Kawamura4I. Oyabu5S. J. Andrews6S. J. Andrews7T. Saito8S. Aoki9T. Nakazawa10Earth System Division, National Institute for Environmental Studies, Tsukuba, JapanFaculty of Education, Miyagi University of Education, Sendai, JapanMeteorology and Glaciology Group, Division for Advanced Research Promotion, National Institute of Polar Research, Tokyo, JapanDepartment of Polar Science, School of Multidisciplinary Sciences, The Graduate University of Advanced Studies (SOKENDAI), Tokyo, JapanBiogeochemistry Research Center, Japan Agency for Marine Science and Technology, Yokosuka, JapanMeteorology and Glaciology Group, Division for Advanced Research Promotion, National Institute of Polar Research, Tokyo, JapanWolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, York, UKformerly at: Center for Environmental Measurement and Analysis, National Institute for Environmental Studies, Tsukuba, JapanEarth System Division, National Institute for Environmental Studies, Tsukuba, JapanCenter for Atmospheric and Oceanic Studies, Graduate School of Science, Tohoku University, Sendai, JapanCenter for Atmospheric and Oceanic Studies, Graduate School of Science, Tohoku University, Sendai, Japan<p>Systematic measurements of atmospheric methane (CH<span class="inline-formula"><sub>4</sub></span>) mole fractions at the northern high latitudes only began in the early 1980s. Although CH<span class="inline-formula"><sub>4</sub></span> measurements from Greenland ice cores consistently covered the period before <span class="inline-formula">∼</span> 1900, no reliable observational record is available for the intermediate period. We newly report a data set of trace gases from the air trapped in firn (an intermediate stage between snow and glacial ice formation) collected at the NGRIP (North Greenland Ice Core Project) site in 2001. We also use a set of published firn air data at the NEEM (North Greenland Eemian ice Drilling) site. The two Arctic firn air data sets are analysed with a firn air transport model, which translates historical variations to depth profiles of trace gases in firn. We examine a variety of possible firn diffusivity profiles, using a suite of measured trace gases, and reconstruct the CH<span class="inline-formula"><sub>4</sub></span> mole fraction by an iterative dating method. Although the reconstructions of the Arctic CH<span class="inline-formula"><sub>4</sub></span> mole fraction before the mid-1970s still has large uncertainties (<span class="inline-formula">></span> 30 ppb – parts per billion), we find a relatively narrow range of atmospheric CH<span class="inline-formula"><sub>4</sub></span> history that is consistent with both depth profiles of NGRIP and NEEM. The atmospheric CH<span class="inline-formula"><sub>4</sub></span> history inferred by this study is more consistent with the atmospheric CH<span class="inline-formula"><sub>4</sub></span> scenario prepared for the NEEM firn modelling than that for the CMIP6 (Climate Model Intercomparison Project Phase 6) experiments. Our study shows that the atmospheric CH<span class="inline-formula"><sub>4</sub></span> scenario used for the NEEM firn modelling is considered to be the current best choice for the Arctic CH<span class="inline-formula"><sub>4</sub></span> history, but it should not be used to tune firn air transport models until being verified by further measurements from sources such as the Arctic ice cores. Given the current difficulty in reconstructing the CH<span class="inline-formula"><sub>4</sub></span> history with low uncertainty from the firn air data sets from Greenland, future sampling and measurements of ice cores at a high-accumulation site may be the only way to accurately reconstruct the atmospheric CH<span class="inline-formula"><sub>4</sub></span> trend over the 20th century.</p>https://acp.copernicus.org/articles/22/6899/2022/acp-22-6899-2022.pdf |
| spellingShingle | T. Umezawa S. Sugawara K. Kawamura K. Kawamura K. Kawamura I. Oyabu S. J. Andrews S. J. Andrews T. Saito S. Aoki T. Nakazawa Towards reconstructing the Arctic atmospheric methane history over the 20th century: measurement and modelling results for the North Greenland Ice Core Project firn Atmospheric Chemistry and Physics |
| title | Towards reconstructing the Arctic atmospheric methane history over the 20th century: measurement and modelling results for the North Greenland Ice Core Project firn |
| title_full | Towards reconstructing the Arctic atmospheric methane history over the 20th century: measurement and modelling results for the North Greenland Ice Core Project firn |
| title_fullStr | Towards reconstructing the Arctic atmospheric methane history over the 20th century: measurement and modelling results for the North Greenland Ice Core Project firn |
| title_full_unstemmed | Towards reconstructing the Arctic atmospheric methane history over the 20th century: measurement and modelling results for the North Greenland Ice Core Project firn |
| title_short | Towards reconstructing the Arctic atmospheric methane history over the 20th century: measurement and modelling results for the North Greenland Ice Core Project firn |
| title_sort | towards reconstructing the arctic atmospheric methane history over the 20th century measurement and modelling results for the north greenland ice core project firn |
| url | https://acp.copernicus.org/articles/22/6899/2022/acp-22-6899-2022.pdf |
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