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 17 O excess (Δ 17 O = δ 17 O−0.52 × δ 18 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 17 O spanning the last 2400 years from the West Antarctic Ice Sheet Divide ice core project shows si...
Published in: | Atmospheric Chemistry and Physics |
---|---|
Main Authors: | , , , , , , , , , , , , , |
Format: | Text |
Language: | English |
Published: |
2018
|
Subjects: | |
Online Access: | https://doi.org/10.5194/acp-14-5749-2014 https://www.atmos-chem-phys.net/14/5749/2014/ |
id |
ftcopernicus:oai:publications.copernicus.org:acp21537 |
---|---|
record_format |
openpolar |
spelling |
ftcopernicus:oai:publications.copernicus.org:acp21537 2023-05-15T13:45:55+02:00 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 Sofen, E. D. Alexander, B. Steig, E. J. Thiemens, M. H. Kunasek, S. A. Amos, H. M. Schauer, A. J. Hastings, M. G. Bautista, J. Jackson, T. L. Vogel, L. E. McConnell, J. R. Pasteris, D. R. Saltzman, E. S. 2018-10-02 application/pdf https://doi.org/10.5194/acp-14-5749-2014 https://www.atmos-chem-phys.net/14/5749/2014/ eng eng doi:10.5194/acp-14-5749-2014 https://www.atmos-chem-phys.net/14/5749/2014/ eISSN: 1680-7324 Text 2018 ftcopernicus https://doi.org/10.5194/acp-14-5749-2014 2019-12-24T09:54:25Z The 17 O excess (Δ 17 O = δ 17 O−0.52 × δ 18 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 17 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 17 O in the most recent 200 years, indicating changes in their formation pathways. The sulfate Δ 17 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 3 , relative to that in the gas phase. Nitrate Δ 17 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 2 in NO x 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 3 production rate in remote low-NO x environments. Using other ice core observations, we rule out drivers for these changes other than variability in extratropical oxidant (OH, O 3 , RO 2 , H 2 O 2 , and reactive halogens) concentrations. However, assuming OH, H 2 O 2 , and O 3 are the main oxidants contributing to sulfate formation, Monte Carlo box model simulations require a large (≥ 260%) increase in the O 3 / OH mole fraction ratio over the Southern Ocean in the early 19th century to match the sulfate Δ 17 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 17 O since the mid-19th century is most likely due to an increased importance of RO 2 over O 3 in NO x cycling and can be explained by a 60–90% decrease in the O 3 / RO 2 mole fraction ratio in the extratropical Southern Hemisphere NO x -source regions. Text Antarc* Antarctic ice core Ice Sheet Southern Ocean Copernicus Publications: E-Journals Antarctic Southern Ocean West Antarctic Ice Sheet Atmospheric Chemistry and Physics 14 11 5749 5769 |
institution |
Open Polar |
collection |
Copernicus Publications: E-Journals |
op_collection_id |
ftcopernicus |
language |
English |
description |
The 17 O excess (Δ 17 O = δ 17 O−0.52 × δ 18 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 17 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 17 O in the most recent 200 years, indicating changes in their formation pathways. The sulfate Δ 17 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 3 , relative to that in the gas phase. Nitrate Δ 17 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 2 in NO x 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 3 production rate in remote low-NO x environments. Using other ice core observations, we rule out drivers for these changes other than variability in extratropical oxidant (OH, O 3 , RO 2 , H 2 O 2 , and reactive halogens) concentrations. However, assuming OH, H 2 O 2 , and O 3 are the main oxidants contributing to sulfate formation, Monte Carlo box model simulations require a large (≥ 260%) increase in the O 3 / OH mole fraction ratio over the Southern Ocean in the early 19th century to match the sulfate Δ 17 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 17 O since the mid-19th century is most likely due to an increased importance of RO 2 over O 3 in NO x cycling and can be explained by a 60–90% decrease in the O 3 / RO 2 mole fraction ratio in the extratropical Southern Hemisphere NO x -source regions. |
format |
Text |
author |
Sofen, E. D. Alexander, B. Steig, E. J. Thiemens, M. H. Kunasek, S. A. Amos, H. M. Schauer, A. J. Hastings, M. G. Bautista, J. Jackson, T. L. Vogel, L. E. McConnell, J. R. Pasteris, D. R. Saltzman, E. S. |
spellingShingle |
Sofen, E. D. Alexander, B. Steig, E. J. Thiemens, M. H. Kunasek, S. A. Amos, H. M. Schauer, A. J. Hastings, M. G. Bautista, J. Jackson, T. L. Vogel, L. E. McConnell, J. R. Pasteris, D. R. Saltzman, E. S. 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 |
author_facet |
Sofen, E. D. Alexander, B. Steig, E. J. Thiemens, M. H. Kunasek, S. A. Amos, H. M. Schauer, A. J. Hastings, M. G. Bautista, J. Jackson, T. L. Vogel, L. E. McConnell, J. R. Pasteris, D. R. Saltzman, E. S. |
author_sort |
Sofen, E. D. |
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_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_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_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 |
publishDate |
2018 |
url |
https://doi.org/10.5194/acp-14-5749-2014 https://www.atmos-chem-phys.net/14/5749/2014/ |
geographic |
Antarctic Southern Ocean West Antarctic Ice Sheet |
geographic_facet |
Antarctic Southern Ocean West Antarctic Ice Sheet |
genre |
Antarc* Antarctic ice core Ice Sheet Southern Ocean |
genre_facet |
Antarc* Antarctic ice core Ice Sheet Southern Ocean |
op_source |
eISSN: 1680-7324 |
op_relation |
doi:10.5194/acp-14-5749-2014 https://www.atmos-chem-phys.net/14/5749/2014/ |
op_doi |
https://doi.org/10.5194/acp-14-5749-2014 |
container_title |
Atmospheric Chemistry and Physics |
container_volume |
14 |
container_issue |
11 |
container_start_page |
5749 |
op_container_end_page |
5769 |
_version_ |
1766232361936093184 |