Photolytic modification of seasonal nitrate isotope cycles in East Antarctica
Nitrate in Antarctic snow has seasonal cycles in its nitrogen and oxygen isotopic ratios that reflect its sources and atmospheric formation processes, and as a result, nitrate archived in Antarctic ice should have great potential to record atmospheric chemistry changes over thousands of years. Howev...
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ftcopernicus:oai:publications.copernicus.org:egusphere105937 2023-05-15T13:38:41+02:00 Photolytic modification of seasonal nitrate isotope cycles in East Antarctica Akers, Pete D. Savarino, Joël Caillon, Nicolas Magand, Olivier Meur, Emmanuel 2022-08-24 application/pdf https://doi.org/10.5194/egusphere-2022-812 https://egusphere.copernicus.org/preprints/2022/egusphere-2022-812/ eng eng doi:10.5194/egusphere-2022-812 https://egusphere.copernicus.org/preprints/2022/egusphere-2022-812/ eISSN: Text 2022 ftcopernicus https://doi.org/10.5194/egusphere-2022-812 2022-08-29T16:22:54Z Nitrate in Antarctic snow has seasonal cycles in its nitrogen and oxygen isotopic ratios that reflect its sources and atmospheric formation processes, and as a result, nitrate archived in Antarctic ice should have great potential to record atmospheric chemistry changes over thousands of years. However, sunlight that strikes the snow surface results in photolytic nitrate loss and isotopic fractionation that can completely obscure the nitrate’s original isotopic values. To gain insight into how photolysis overwrites the seasonal atmospheric cycles, we collected 244 snow samples along a 850 km transect of East Antarctica during the 2013–2014 CHICTABA traverse. The CHICTABA route’s limited elevation change, consistent distance between the coast and the high interior plateau, and intermediate accumulation rates offered a gentle environmental gradient ideal for studying the competing pre- and post-depositional influences on archived nitrate isotopes. We find that nitrate isotopes in snow along the transect are indeed notably modified by photolysis after deposition, and drier sites have more intense photolytic impacts. Still, an imprint of the original seasonal cycles of atmospheric nitrate isotopes is still present in the top 1–2 m of the snowpack and likely preserved through archiving in glacial ice at these sites. Despite this preservation, reconstructing past atmospheric values from archived nitrate along CHICTABA and in similar transitional regions remains a difficult challenge without having an independent proxy for photolytic loss to correct for post-depositional isotopic changes. Nevertheless, nitrate isotopes should function as a proxy for snow accumulation rate in such regions if multiple years of deposition are aggregated to remove the seasonal cycles, and this application can prove highly valuable in its own right. Text Antarc* Antarctic Antarctica East Antarctica Copernicus Publications: E-Journals Antarctic East Antarctica |
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Copernicus Publications: E-Journals |
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English |
description |
Nitrate in Antarctic snow has seasonal cycles in its nitrogen and oxygen isotopic ratios that reflect its sources and atmospheric formation processes, and as a result, nitrate archived in Antarctic ice should have great potential to record atmospheric chemistry changes over thousands of years. However, sunlight that strikes the snow surface results in photolytic nitrate loss and isotopic fractionation that can completely obscure the nitrate’s original isotopic values. To gain insight into how photolysis overwrites the seasonal atmospheric cycles, we collected 244 snow samples along a 850 km transect of East Antarctica during the 2013–2014 CHICTABA traverse. The CHICTABA route’s limited elevation change, consistent distance between the coast and the high interior plateau, and intermediate accumulation rates offered a gentle environmental gradient ideal for studying the competing pre- and post-depositional influences on archived nitrate isotopes. We find that nitrate isotopes in snow along the transect are indeed notably modified by photolysis after deposition, and drier sites have more intense photolytic impacts. Still, an imprint of the original seasonal cycles of atmospheric nitrate isotopes is still present in the top 1–2 m of the snowpack and likely preserved through archiving in glacial ice at these sites. Despite this preservation, reconstructing past atmospheric values from archived nitrate along CHICTABA and in similar transitional regions remains a difficult challenge without having an independent proxy for photolytic loss to correct for post-depositional isotopic changes. Nevertheless, nitrate isotopes should function as a proxy for snow accumulation rate in such regions if multiple years of deposition are aggregated to remove the seasonal cycles, and this application can prove highly valuable in its own right. |
format |
Text |
author |
Akers, Pete D. Savarino, Joël Caillon, Nicolas Magand, Olivier Meur, Emmanuel |
spellingShingle |
Akers, Pete D. Savarino, Joël Caillon, Nicolas Magand, Olivier Meur, Emmanuel Photolytic modification of seasonal nitrate isotope cycles in East Antarctica |
author_facet |
Akers, Pete D. Savarino, Joël Caillon, Nicolas Magand, Olivier Meur, Emmanuel |
author_sort |
Akers, Pete D. |
title |
Photolytic modification of seasonal nitrate isotope cycles in East Antarctica |
title_short |
Photolytic modification of seasonal nitrate isotope cycles in East Antarctica |
title_full |
Photolytic modification of seasonal nitrate isotope cycles in East Antarctica |
title_fullStr |
Photolytic modification of seasonal nitrate isotope cycles in East Antarctica |
title_full_unstemmed |
Photolytic modification of seasonal nitrate isotope cycles in East Antarctica |
title_sort |
photolytic modification of seasonal nitrate isotope cycles in east antarctica |
publishDate |
2022 |
url |
https://doi.org/10.5194/egusphere-2022-812 https://egusphere.copernicus.org/preprints/2022/egusphere-2022-812/ |
geographic |
Antarctic East Antarctica |
geographic_facet |
Antarctic East Antarctica |
genre |
Antarc* Antarctic Antarctica East Antarctica |
genre_facet |
Antarc* Antarctic Antarctica East Antarctica |
op_source |
eISSN: |
op_relation |
doi:10.5194/egusphere-2022-812 https://egusphere.copernicus.org/preprints/2022/egusphere-2022-812/ |
op_doi |
https://doi.org/10.5194/egusphere-2022-812 |
_version_ |
1766109505960017920 |