WAIS Divide ice core suggests sustained changes in the atmospheric formation pathways of sulfate and nitrate since the 19th century in the extratropical Southern Hemisphere
The <sup>17</sup>O excess (Δ<sup>17</sup>O = δ<sup>17</sup>O−0.52 × δ<sup>18</sup>O) of sulfate and nitrate reflects the relative importance of their different production pathways in the atmosphere. A new record of sulfate and nitrate Δ<su...
| Main Authors: | , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-06-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/14/5749/2014/acp-14-5749-2014.pdf |
| _version_ | 1828820680506867712 |
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| author | E. D. Sofen B. Alexander E. J. Steig M. H. Thiemens S. A. Kunasek H. M. Amos A. J. Schauer M. G. Hastings J. Bautista T. L. Jackson L. E. Vogel J. R. McConnell D. R. Pasteris E. S. Saltzman |
| author_facet | E. D. Sofen B. Alexander E. J. Steig M. H. Thiemens S. A. Kunasek H. M. Amos A. J. Schauer M. G. Hastings J. Bautista T. L. Jackson L. E. Vogel J. R. McConnell D. R. Pasteris E. S. Saltzman |
| author_sort | E. D. Sofen |
| collection | DOAJ |
| description | The <sup>17</sup>O excess
(Δ<sup>17</sup>O = δ<sup>17</sup>O−0.52 × δ<sup>18</sup>O) of
sulfate and nitrate reflects the relative importance of their different
production pathways in the atmosphere. A new record of sulfate and nitrate
Δ<sup>17</sup>O spanning the last 2400 years from the West Antarctic Ice Sheet
Divide ice core project shows significant changes in both sulfate and nitrate
Δ<sup>17</sup>O in the most recent 200 years, indicating changes in their
formation pathways. The sulfate Δ<sup>17</sup>O record exhibits a
1.1 ‰ increase in the early 19th century from
(2.4 ± 0.2) ‰ to (3.5 ± 0.2) ‰, which suggests that
an additional 12–18% of sulfate formation occurs via aqueous-phase
production by O<sub>3</sub>, relative to that in the gas phase. Nitrate
Δ<sup>17</sup>O gradually decreases over the whole record, with a more rapid
decrease between the mid-19th century and the present day of 5.6 ‰,
indicating an increasing importance of RO<sub>2</sub> in NO<sub>x</sub> cycling
between the mid-19th century and the present day in the mid- to high-latitude
Southern Hemisphere. The former has implications for the climate impacts of
sulfate aerosol, while the latter has implications for the tropospheric O<sub>3</sub>
production rate in remote low-NO<sub>x</sub> environments. Using other ice
core observations, we rule out drivers for these changes other than
variability in extratropical oxidant (OH, O<sub>3</sub>,
RO<sub>2</sub>, H<sub>2</sub>O<sub>2</sub>, and
reactive halogens) concentrations. However,
assuming OH, H<sub>2</sub>O<sub>2</sub>, and
O<sub>3</sub> are the main oxidants contributing to sulfate formation, Monte Carlo
box model simulations require a large (≥ 260%) increase in the
O<sub>3</sub> / OH mole fraction ratio over the Southern Ocean in the early 19th
century to match the sulfate Δ<sup>17</sup>O record. This unlikely scenario
points to a~deficiency in our understanding of sulfur chemistry and suggests
other oxidants may play an important role in sulfate formation in the mid- to
high-latitude marine boundary layer. The observed decrease in nitrate
Δ<sup>17</sup>O since the mid-19th century is most likely due to an increased
importance of RO<sub>2</sub> over O<sub>3</sub> in NO<sub>x</sub> cycling and can be
explained by a 60–90% decrease in the O<sub>3</sub> / RO<sub>2</sub> mole fraction
ratio in the extratropical Southern Hemisphere NO<sub>x</sub>-source
regions. |
| first_indexed | 2024-12-12T12:38:36Z |
| format | Article |
| id | doaj.art-1d25409191e24617a304b96e5f143ef7 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-12T12:38:36Z |
| publishDate | 2014-06-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-1d25409191e24617a304b96e5f143ef72022-12-22T00:24:16ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242014-06-0114115749576910.5194/acp-14-5749-2014WAIS Divide ice core suggests sustained changes in the atmospheric formation pathways of sulfate and nitrate since the 19th century in the extratropical Southern HemisphereE. D. Sofen0B. Alexander1E. J. Steig2M. H. Thiemens3S. A. Kunasek4H. M. Amos5A. J. Schauer6M. G. Hastings7J. Bautista8T. L. Jackson9L. E. Vogel10J. R. McConnell11D. R. Pasteris12E. S. Saltzman13Department of Atmospheric Sciences, University of Washington, Seattle, WA 98195, USADepartment of Atmospheric Sciences, University of Washington, Seattle, WA 98195, USADepartment of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USAUniversity of California at San Diego, La Jolla, CA 92093, USADepartment of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USADepartment of Atmospheric Sciences, University of Washington, Seattle, WA 98195, USADepartment of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USADepartment of Atmospheric Sciences, University of Washington, Seattle, WA 98195, USADepartment of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USAUniversity of California at San Diego, La Jolla, CA 92093, USAJoint Institute for the Study of the Atmosphere and the Ocean, University of Washington, Seattle, WA 98195, USADivision of Hydrologic Sciences, Desert Research Institute, Reno, NV 89512, USADivision of Hydrologic Sciences, Desert Research Institute, Reno, NV 89512, USADepartment of Earth System Science, University of California at Irvine, Irvine, CA 92697, USAThe <sup>17</sup>O excess (Δ<sup>17</sup>O = δ<sup>17</sup>O−0.52 × δ<sup>18</sup>O) of sulfate and nitrate reflects the relative importance of their different production pathways in the atmosphere. A new record of sulfate and nitrate Δ<sup>17</sup>O spanning the last 2400 years from the West Antarctic Ice Sheet Divide ice core project shows significant changes in both sulfate and nitrate Δ<sup>17</sup>O in the most recent 200 years, indicating changes in their formation pathways. The sulfate Δ<sup>17</sup>O record exhibits a 1.1 ‰ increase in the early 19th century from (2.4 ± 0.2) ‰ to (3.5 ± 0.2) ‰, which suggests that an additional 12–18% of sulfate formation occurs via aqueous-phase production by O<sub>3</sub>, relative to that in the gas phase. Nitrate Δ<sup>17</sup>O gradually decreases over the whole record, with a more rapid decrease between the mid-19th century and the present day of 5.6 ‰, indicating an increasing importance of RO<sub>2</sub> in NO<sub>x</sub> cycling between the mid-19th century and the present day in the mid- to high-latitude Southern Hemisphere. The former has implications for the climate impacts of sulfate aerosol, while the latter has implications for the tropospheric O<sub>3</sub> production rate in remote low-NO<sub>x</sub> environments. Using other ice core observations, we rule out drivers for these changes other than variability in extratropical oxidant (OH, O<sub>3</sub>, RO<sub>2</sub>, H<sub>2</sub>O<sub>2</sub>, and reactive halogens) concentrations. However, assuming OH, H<sub>2</sub>O<sub>2</sub>, and O<sub>3</sub> are the main oxidants contributing to sulfate formation, Monte Carlo box model simulations require a large (≥ 260%) increase in the O<sub>3</sub> / OH mole fraction ratio over the Southern Ocean in the early 19th century to match the sulfate Δ<sup>17</sup>O record. This unlikely scenario points to a~deficiency in our understanding of sulfur chemistry and suggests other oxidants may play an important role in sulfate formation in the mid- to high-latitude marine boundary layer. The observed decrease in nitrate Δ<sup>17</sup>O since the mid-19th century is most likely due to an increased importance of RO<sub>2</sub> over O<sub>3</sub> in NO<sub>x</sub> cycling and can be explained by a 60–90% decrease in the O<sub>3</sub> / RO<sub>2</sub> mole fraction ratio in the extratropical Southern Hemisphere NO<sub>x</sub>-source regions.http://www.atmos-chem-phys.net/14/5749/2014/acp-14-5749-2014.pdf |
| spellingShingle | E. D. Sofen B. Alexander E. J. Steig M. H. Thiemens S. A. Kunasek H. M. Amos A. J. Schauer M. G. Hastings J. Bautista T. L. Jackson L. E. Vogel J. R. McConnell D. R. Pasteris E. S. Saltzman WAIS Divide ice core suggests sustained changes in the atmospheric formation pathways of sulfate and nitrate since the 19th century in the extratropical Southern Hemisphere Atmospheric Chemistry and Physics |
| title | WAIS Divide ice core suggests sustained changes in the atmospheric formation pathways of sulfate and nitrate since the 19th century in the extratropical Southern Hemisphere |
| title_full | WAIS Divide ice core suggests sustained changes in the atmospheric formation pathways of sulfate and nitrate since the 19th century in the extratropical Southern Hemisphere |
| title_fullStr | WAIS Divide ice core suggests sustained changes in the atmospheric formation pathways of sulfate and nitrate since the 19th century in the extratropical Southern Hemisphere |
| title_full_unstemmed | WAIS Divide ice core suggests sustained changes in the atmospheric formation pathways of sulfate and nitrate since the 19th century in the extratropical Southern Hemisphere |
| title_short | WAIS Divide ice core suggests sustained changes in the atmospheric formation pathways of sulfate and nitrate since the 19th century in the extratropical Southern Hemisphere |
| title_sort | wais divide ice core suggests sustained changes in the atmospheric formation pathways of sulfate and nitrate since the 19th century in the extratropical southern hemisphere |
| url | http://www.atmos-chem-phys.net/14/5749/2014/acp-14-5749-2014.pdf |
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