Secular change in atmospheric Ar∕N 2 and its implications for ocean heat uptake and Brewer–Dobson circulation
Systematic measurements of the atmospheric Ar∕N 2 ratio have been made at ground-based stations in Japan and Antarctica since 2012. Clear seasonal cycles of the Ar∕N 2 ratio with summertime maxima were found at middle- to high-latitude stations, with seasonal amplitudes increasing with increasing la...
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ftdoajarticles:oai:doaj.org/article:5dde2f3ebaf846dd83055a3137e2a268 2023-05-15T14:02:16+02:00 Secular change in atmospheric Ar∕N 2 and its implications for ocean heat uptake and Brewer–Dobson circulation S. Ishidoya S. Sugawara Y. Tohjima D. Goto K. Ishijima Y. Niwa N. Aoki S. Murayama 2021-02-01T00:00:00Z https://doi.org/10.5194/acp-21-1357-2021 https://doaj.org/article/5dde2f3ebaf846dd83055a3137e2a268 EN eng Copernicus Publications https://acp.copernicus.org/articles/21/1357/2021/acp-21-1357-2021.pdf https://doaj.org/toc/1680-7316 https://doaj.org/toc/1680-7324 doi:10.5194/acp-21-1357-2021 1680-7316 1680-7324 https://doaj.org/article/5dde2f3ebaf846dd83055a3137e2a268 Atmospheric Chemistry and Physics, Vol 21, Pp 1357-1373 (2021) Physics QC1-999 Chemistry QD1-999 article 2021 ftdoajarticles https://doi.org/10.5194/acp-21-1357-2021 2022-12-31T15:55:03Z Systematic measurements of the atmospheric Ar∕N 2 ratio have been made at ground-based stations in Japan and Antarctica since 2012. Clear seasonal cycles of the Ar∕N 2 ratio with summertime maxima were found at middle- to high-latitude stations, with seasonal amplitudes increasing with increasing latitude. Eight years of the observed Ar∕N 2 ratio at Tsukuba (TKB) and Hateruma (HAT), Japan, showed interannual variations in phase with the observed variations in the global ocean heat content (OHC). We calculated secularly increasing trends of 0.75 ± 0.30 and 0.89 ± 0.60 per meg per year from the Ar∕N 2 ratio observed at TKB and HAT, respectively, although these trend values are influenced by large interannual variations. In order to examine the possibility of the secular trend in the surface Ar∕N 2 ratio being modified significantly by the gravitational separation in the stratosphere, two-dimensional model simulations were carried out by arbitrarily modifying the mass stream function in the model to simulate either a weakening or an enhancement of the Brewer–Dobson circulation (BDC). The secular trend of the Ar∕N 2 ratio at TKB, corrected for gravitational separation under the assumption of weakening (enhancement) of BDC simulated by the 2-D model, was 0.60 ± 0.30 (0.88 ± 0.30) per meg per year. By using a conversion factor of 3.5 × 10 −23 per meg per joule by assuming a one-box ocean with a temperature of 3.5 ∘ C, average OHC increase rates of 17.1 ± 8.6 ZJ yr −1 and 25.1 ± 8.6 ZJ yr −1 for the period 2012–2019 were estimated from the corrected secular trends of the Ar∕N 2 ratio for the weakened- and enhanced-BDC conditions, respectively. Both OHC increase rates from the uncorrected- and weakened-BDC secular trends of the Ar∕N 2 ratio are consistent with 12.2 ± 1.2 ZJ yr −1 reported by ocean temperature measurements, while that from the enhanced-BDC is outside of the range of the uncertainties. Although the effect of the actual atmospheric circulation on the Ar∕N 2 ratio is still unclear and longer-term ... Article in Journal/Newspaper Antarc* Antarctica Directory of Open Access Journals: DOAJ Articles Atmospheric Chemistry and Physics 21 2 1357 1373 |
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Physics QC1-999 Chemistry QD1-999 |
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Physics QC1-999 Chemistry QD1-999 S. Ishidoya S. Sugawara Y. Tohjima D. Goto K. Ishijima Y. Niwa N. Aoki S. Murayama Secular change in atmospheric Ar∕N 2 and its implications for ocean heat uptake and Brewer–Dobson circulation |
topic_facet |
Physics QC1-999 Chemistry QD1-999 |
description |
Systematic measurements of the atmospheric Ar∕N 2 ratio have been made at ground-based stations in Japan and Antarctica since 2012. Clear seasonal cycles of the Ar∕N 2 ratio with summertime maxima were found at middle- to high-latitude stations, with seasonal amplitudes increasing with increasing latitude. Eight years of the observed Ar∕N 2 ratio at Tsukuba (TKB) and Hateruma (HAT), Japan, showed interannual variations in phase with the observed variations in the global ocean heat content (OHC). We calculated secularly increasing trends of 0.75 ± 0.30 and 0.89 ± 0.60 per meg per year from the Ar∕N 2 ratio observed at TKB and HAT, respectively, although these trend values are influenced by large interannual variations. In order to examine the possibility of the secular trend in the surface Ar∕N 2 ratio being modified significantly by the gravitational separation in the stratosphere, two-dimensional model simulations were carried out by arbitrarily modifying the mass stream function in the model to simulate either a weakening or an enhancement of the Brewer–Dobson circulation (BDC). The secular trend of the Ar∕N 2 ratio at TKB, corrected for gravitational separation under the assumption of weakening (enhancement) of BDC simulated by the 2-D model, was 0.60 ± 0.30 (0.88 ± 0.30) per meg per year. By using a conversion factor of 3.5 × 10 −23 per meg per joule by assuming a one-box ocean with a temperature of 3.5 ∘ C, average OHC increase rates of 17.1 ± 8.6 ZJ yr −1 and 25.1 ± 8.6 ZJ yr −1 for the period 2012–2019 were estimated from the corrected secular trends of the Ar∕N 2 ratio for the weakened- and enhanced-BDC conditions, respectively. Both OHC increase rates from the uncorrected- and weakened-BDC secular trends of the Ar∕N 2 ratio are consistent with 12.2 ± 1.2 ZJ yr −1 reported by ocean temperature measurements, while that from the enhanced-BDC is outside of the range of the uncertainties. Although the effect of the actual atmospheric circulation on the Ar∕N 2 ratio is still unclear and longer-term ... |
format |
Article in Journal/Newspaper |
author |
S. Ishidoya S. Sugawara Y. Tohjima D. Goto K. Ishijima Y. Niwa N. Aoki S. Murayama |
author_facet |
S. Ishidoya S. Sugawara Y. Tohjima D. Goto K. Ishijima Y. Niwa N. Aoki S. Murayama |
author_sort |
S. Ishidoya |
title |
Secular change in atmospheric Ar∕N 2 and its implications for ocean heat uptake and Brewer–Dobson circulation |
title_short |
Secular change in atmospheric Ar∕N 2 and its implications for ocean heat uptake and Brewer–Dobson circulation |
title_full |
Secular change in atmospheric Ar∕N 2 and its implications for ocean heat uptake and Brewer–Dobson circulation |
title_fullStr |
Secular change in atmospheric Ar∕N 2 and its implications for ocean heat uptake and Brewer–Dobson circulation |
title_full_unstemmed |
Secular change in atmospheric Ar∕N 2 and its implications for ocean heat uptake and Brewer–Dobson circulation |
title_sort |
secular change in atmospheric ar∕n 2 and its implications for ocean heat uptake and brewer–dobson circulation |
publisher |
Copernicus Publications |
publishDate |
2021 |
url |
https://doi.org/10.5194/acp-21-1357-2021 https://doaj.org/article/5dde2f3ebaf846dd83055a3137e2a268 |
genre |
Antarc* Antarctica |
genre_facet |
Antarc* Antarctica |
op_source |
Atmospheric Chemistry and Physics, Vol 21, Pp 1357-1373 (2021) |
op_relation |
https://acp.copernicus.org/articles/21/1357/2021/acp-21-1357-2021.pdf https://doaj.org/toc/1680-7316 https://doaj.org/toc/1680-7324 doi:10.5194/acp-21-1357-2021 1680-7316 1680-7324 https://doaj.org/article/5dde2f3ebaf846dd83055a3137e2a268 |
op_doi |
https://doi.org/10.5194/acp-21-1357-2021 |
container_title |
Atmospheric Chemistry and Physics |
container_volume |
21 |
container_issue |
2 |
container_start_page |
1357 |
op_container_end_page |
1373 |
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1766272422395248640 |