Articles | Volume 25, issue 19
https://doi.org/10.5194/acp-25-11895-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-25-11895-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
02 Oct 2025
Research article |
| 02 Oct 2025
| 02 Oct 2025
Stratospheric δ13CO2 observed over Japan and its governing processes
Satoshi Sugawara
CORRESPONDING AUTHOR
Faculty of Education, Miyagi University of Education, Sendai 980-0845, Japan
Shinji Morimoto
Center for Atmospheric and Oceanic Studies, Tohoku University, Sendai 980-8578, Japan
Shigeyuki Ishidoya
National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8569, Japan
Taku Umezawa
National Institute for Environmental Studies, Tsukuba 305-8506, Japan
Center for Atmospheric and Oceanic Studies, Tohoku University, Sendai 980-8578, Japan
Shuji Aoki
Center for Atmospheric and Oceanic Studies, Tohoku University, Sendai 980-8578, Japan
Takakiyo Nakazawa
Center for Atmospheric and Oceanic Studies, Tohoku University, Sendai 980-8578, Japan
Sakae Toyoda
School of Materials and Chemical Technology, Institute of Science Tokyo, Yokohama 226-8501, Japan
Kentaro Ishijima
Meteorological Research Institute, Japan Meteorological Agency, Tsukuba 305-0052, Japan
Daisuke Goto
National Institute of Polar Research, Tachikawa 190-8518, Japan
Hideyuki Honda
Center for Atmospheric and Oceanic Studies, Tohoku University, Sendai 980-8578, Japan
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Stratospheric air samples have been collected using balloon-borne cryogenic samplers over Japan and analyzed for the isotopic and elemental ratios of noble gases. We report the results of the first study on the vertical changes of Kr, Xe, and Ne in the stratosphere. The observed results suggest that not only gravitational separation but also kinetic fractionation occurred in the stratosphere. The kinetic fractionations would be an additional tool to diagnose stratospheric transport processes.
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The 18O/16O ratio of atmospheric oxygen, δatm(18O), is higher than that of ocean water due to isotopic effects during biospheric activities. This is known as the Dole–Morita effect, and its millennial-scale variations are recorded in ice cores. However, small variations of δatm(18O) in the present day have never been detected so far. This paper presents the first observations of diurnal, seasonal, and secular variations in δatm(18O) and applies them to evaluate oxygen, carbon, and water cycles.
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Greenhouse gas methane in the Arctic atmosphere has not been accurately reported for 1900–1980 from either direct observations or ice core reconstructions. By using trace gas data from firn (compacted snow layers above ice sheet), air samples at two Greenland sites, and a firn air transport model, this study suggests a likely range of the Arctic methane reconstruction for the 20th century. Atmospheric scenarios from two previous studies are also evaluated for consistency with the firn data sets.
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The surface Ar / N2 ratio showed not only secular increasing trends, but also interannual variations in phase with the global ocean heat content (OHC). Sensitivity test by using a two-dimensional model indicated that the secular trend in the Ar / N2 ratio is modified by the gravitational separation in the stratosphere. The analytical results imply that the surface Ar/N2 ratio is an important tracer for detecting spatiotemporally integrated changes in OHC and stratospheric circulation.
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Preprint archived
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Shigeyuki Ishidoya, Kazuhiro Tsuboi, Hiroaki Kondo, Kentaro Ishijima, Nobuyuki Aoki, Hidekazu Matsueda, and Kazuyuki Saito
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A method evaluating techniques for carbon neutrality, such as carbon capture and storage (CCS), is important. This study presents a method to evaluate CO2 emissions from a cement plant based on atmospheric O2 and CO2 measurements. The method will also be useful for evaluating CO2 capture from flue gas at CCS plants, since the plants remove CO2 from the atmosphere without causing any O2 changes, just as cement plants do, differing only in the direction of CO2 exchange with the atmosphere.
Kazuki Kamezaki, Sebastian O. Danielache, Shigeyuki Ishidoya, Takahisa Maeda, and Shohei Murayama
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2023-209, https://doi.org/10.5194/amt-2023-209, 2023
Revised manuscript not accepted
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Recently, MIRA Pico, a portable continuous carbonyl sulfide (COS) concentration analyzer using mid-infrared absorption, has been released. MIRA Pico has a lower cost and is smaller than conventional laser COS analyzers. However, actual COS atmospheric measurement results using MIRA Pico have not yet been reported. In this study, we modified and tested the MIRA Pico for atmospheric COS concentration measurements. We used the modified MIRA Pico for observations at Tsukuba, Japan.
Sourish Basu, Xin Lan, Edward Dlugokencky, Sylvia Michel, Stefan Schwietzke, John B. Miller, Lori Bruhwiler, Youmi Oh, Pieter P. Tans, Francesco Apadula, Luciana V. Gatti, Armin Jordan, Jaroslaw Necki, Motoki Sasakawa, Shinji Morimoto, Tatiana Di Iorio, Haeyoung Lee, Jgor Arduini, and Giovanni Manca
Atmos. Chem. Phys., 22, 15351–15377, https://doi.org/10.5194/acp-22-15351-2022, https://doi.org/10.5194/acp-22-15351-2022, 2022
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Atmospheric methane (CH4) has been growing steadily since 2007 for reasons that are not well understood. Here we determine sources of methane using a technique informed by atmospheric measurements of CH4 and its isotopologue 13CH4. Measurements of 13CH4 provide for better separation of microbial, fossil, and fire sources of methane than CH4 measurements alone. Compared to previous assessments such as the Global Carbon Project, we find a larger microbial contribution to the post-2007 increase.
Nobuyuki Aoki, Shigeyuki Ishidoya, Shohei Murayama, and Nobuhiro Matsumoto
Atmos. Meas. Tech., 15, 5969–5983, https://doi.org/10.5194/amt-15-5969-2022, https://doi.org/10.5194/amt-15-5969-2022, 2022
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The CO2 concentration in a cylinder is affected by carbon dioxide (CO2) adsorption to a cylinder’s internal surface and fractionation of CO2 and air in the preparation of standard mixtures. We demonstrate that the effects make the CO2 molar fractions deviate in standard mixtures prepared by diluting pure CO2 with air three times. This means that CO2 standard gases are difficult to gravimetrically prepare through multistep dilution.
Naveen Chandra, Prabir K. Patra, Yousuke Niwa, Akihiko Ito, Yosuke Iida, Daisuke Goto, Shinji Morimoto, Masayuki Kondo, Masayuki Takigawa, Tomohiro Hajima, and Michio Watanabe
Atmos. Chem. Phys., 22, 9215–9243, https://doi.org/10.5194/acp-22-9215-2022, https://doi.org/10.5194/acp-22-9215-2022, 2022
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This paper is intended to accomplish two goals: (1) quantify mean and uncertainty in non-fossil-fuel CO2 fluxes estimated by inverse modeling and (2) provide in-depth analyses of regional CO2 fluxes in support of emission mitigation policymaking. CO2 flux variability and trends are discussed concerning natural climate variability and human disturbances using multiple lines of evidence.
Shigeyuki Ishidoya, Kazuhiro Tsuboi, Yosuke Niwa, Hidekazu Matsueda, Shohei Murayama, Kentaro Ishijima, and Kazuyuki Saito
Atmos. Chem. Phys., 22, 6953–6970, https://doi.org/10.5194/acp-22-6953-2022, https://doi.org/10.5194/acp-22-6953-2022, 2022
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The atmospheric O2 / N2 ratio and CO2 concentration over the western North Pacific are presented. We found significant modification of the seasonal APO cycle in the middle troposphere due to the interhemispheric mixing of air. APO driven by the net marine biological activities indicated annual sea–air O2 flux during El Niño. Terrestrial biospheric and oceanic CO2 uptakes during 2012–2019 were estimated to be 1.8 and 2.8 Pg C a−1, respectively.
Taku Umezawa, Satoshi Sugawara, Kenji Kawamura, Ikumi Oyabu, Stephen J. Andrews, Takuya Saito, Shuji Aoki, and Takakiyo Nakazawa
Atmos. Chem. Phys., 22, 6899–6917, https://doi.org/10.5194/acp-22-6899-2022, https://doi.org/10.5194/acp-22-6899-2022, 2022
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Greenhouse gas methane in the Arctic atmosphere has not been accurately reported for 1900–1980 from either direct observations or ice core reconstructions. By using trace gas data from firn (compacted snow layers above ice sheet), air samples at two Greenland sites, and a firn air transport model, this study suggests a likely range of the Arctic methane reconstruction for the 20th century. Atmospheric scenarios from two previous studies are also evaluated for consistency with the firn data sets.
Ikumi Oyabu, Kenji Kawamura, Tsutomu Uchida, Shuji Fujita, Kyotaro Kitamura, Motohiro Hirabayashi, Shuji Aoki, Shinji Morimoto, Takakiyo Nakazawa, Jeffrey P. Severinghaus, and Jacob D. Morgan
The Cryosphere, 15, 5529–5555, https://doi.org/10.5194/tc-15-5529-2021, https://doi.org/10.5194/tc-15-5529-2021, 2021
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We present O2/N2 and Ar/N2 records from the Dome Fuji ice core through the bubbly ice, bubble–clathrate transition, and clathrate ice zones without gas-loss fractionation. The insolation signal is preserved through the clathrate formation. The relationship between Ar/Ν2 and Ο2/Ν2 suggests that the fractionation for the bubble–clathrate transition is mass independent, while the bubble close-off process involves a combination of mass-independent and mass-dependent fractionation for O2 and Ar.
Nobuyuki Aoki, Shigeyuki Ishidoya, Yasunori Tohjima, Shinji Morimoto, Ralph F. Keeling, Adam Cox, Shuichiro Takebayashi, and Shohei Murayama
Atmos. Meas. Tech., 14, 6181–6193, https://doi.org/10.5194/amt-14-6181-2021, https://doi.org/10.5194/amt-14-6181-2021, 2021
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Observing the minimal long-term change in atmospheric O2 molar fraction combined with CO2 observation enables us to estimate terrestrial biospheric and oceanic CO2 uptakes separately. In this study, we firstly identified the span offset between the laboratory O2 scales using our developed high-precision standard mixtures, suggesting that the result may allow us to estimate terrestrial biospheric and oceanic CO2 uptakes precisely.
Yosuke Niwa, Yousuke Sawa, Hideki Nara, Toshinobu Machida, Hidekazu Matsueda, Taku Umezawa, Akihiko Ito, Shin-Ichiro Nakaoka, Hiroshi Tanimoto, and Yasunori Tohjima
Atmos. Chem. Phys., 21, 9455–9473, https://doi.org/10.5194/acp-21-9455-2021, https://doi.org/10.5194/acp-21-9455-2021, 2021
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Fires in Equatorial Asia release a large amount of carbon into the atmosphere. Extensively using high-precision atmospheric carbon dioxide (CO2) data from a commercial aircraft observation project, we estimated fire carbon emissions in Equatorial Asia induced by the big El Niño event in 2015. Additional shipboard measurement data elucidated the validity of the analysis and the best estimate indicated 273 Tg C for fire emissions during September–October 2015.
Shigeyuki Ishidoya, Satoshi Sugawara, Yasunori Tohjima, Daisuke Goto, Kentaro Ishijima, Yosuke Niwa, Nobuyuki Aoki, and Shohei Murayama
Atmos. Chem. Phys., 21, 1357–1373, https://doi.org/10.5194/acp-21-1357-2021, https://doi.org/10.5194/acp-21-1357-2021, 2021
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The surface Ar / N2 ratio showed not only secular increasing trends, but also interannual variations in phase with the global ocean heat content (OHC). Sensitivity test by using a two-dimensional model indicated that the secular trend in the Ar / N2 ratio is modified by the gravitational separation in the stratosphere. The analytical results imply that the surface Ar/N2 ratio is an important tracer for detecting spatiotemporally integrated changes in OHC and stratospheric circulation.
Ikumi Oyabu, Kenji Kawamura, Kyotaro Kitamura, Remi Dallmayr, Akihiro Kitamura, Chikako Sawada, Jeffrey P. Severinghaus, Ross Beaudette, Anaïs Orsi, Satoshi Sugawara, Shigeyuki Ishidoya, Dorthe Dahl-Jensen, Kumiko Goto-Azuma, Shuji Aoki, and Takakiyo Nakazawa
Atmos. Meas. Tech., 13, 6703–6731, https://doi.org/10.5194/amt-13-6703-2020, https://doi.org/10.5194/amt-13-6703-2020, 2020
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Air in polar ice cores provides information on past atmosphere and climate. We present a new method for simultaneously measuring eight gases (CH4, N2O and CO2 concentrations; isotopic ratios of N2 and O2; elemental ratios between N2, O2 and Ar; and total air content) from single ice-core samples with high precision.
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Short summary
We have collected stratospheric air samples using balloon-borne cryogenic samplers over Japan since 1985 and analyzed them for δ13CO2. δ13CO2 has decreased through time in the mid-stratosphere with an average rate of change of −0.026 ± 0.001 ‰ yr−1. We found that stratospheric δ13CO2 variations are governed by airborne production of 13C-depleted CO2 by CH4 oxidation, gravitational separation, and propagation of the decreasing tropospheric δ13CO2 trend into the stratosphere.
We have collected stratospheric air samples using balloon-borne cryogenic samplers over Japan...
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