A 60-year atmospheric nitrate isotope record from a southeastern Greenland ice core with minimal postdepositional alteration
<p>Stable isotopes of atmospheric nitrate (NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/>&...
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| Main Authors: | , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2025-06-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/25/5727/2025/acp-25-5727-2025.pdf |
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| Summary: | <p>Stable isotopes of atmospheric nitrate (NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="5c4cefaf8b78d41c1ce2f2ef151f712f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-5727-2025-ie00001.svg" width="9pt" height="16pt" src="acp-25-5727-2025-ie00001.png"/></svg:svg></span></span>) are valuable tools for tracing nitrogen sources and processes; however, their signals in ice core records are often disrupted by postdepositional processes. The ice core from the southeastern Dome (SE-Dome) in Greenland is a potential record of variations in atmospheric chemistry that has experienced a lower postdepositional effect owing to a high accumulation rate (<span class="inline-formula">∼1</span> m water equivalent per year). Herein, we report 60-year (1959–2014) <span class="inline-formula"><i>δ</i><sup>15</sup></span>N(NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="0723f17b5be9fc41c36a5585631feb47"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-5727-2025-ie00002.svg" width="9pt" height="16pt" src="acp-25-5727-2025-ie00002.png"/></svg:svg></span></span>) and <span class="inline-formula">Δ<sup>17</sup></span>O(NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="a6a4c5911a740e8377438efb607d4b86"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-5727-2025-ie00003.svg" width="9pt" height="16pt" src="acp-25-5727-2025-ie00003.png"/></svg:svg></span></span>) records from the SE-Dome ice core. The <span class="inline-formula"><i>δ</i><sup>15</sup></span>N(NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="7de8959157e6c258409d4c11688ca166"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-5727-2025-ie00004.svg" width="9pt" height="16pt" src="acp-25-5727-2025-ie00004.png"/></svg:svg></span></span>) decreased from 1960 to 1974 and exhibited clear seasonal changes (high in summer and low in winter). The <span class="inline-formula">Δ<sup>17</sup></span>O(NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M10" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="78ed0f7e81615226176402cdd6a1afd5"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-5727-2025-ie00005.svg" width="9pt" height="16pt" src="acp-25-5727-2025-ie00005.png"/></svg:svg></span></span>) did not exhibit any significant long-term trends, but it did contain seasonal patterns. The mass-weighted annual average of <span class="inline-formula"><i>δ</i><sup>15</sup></span>N(NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M12" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="ee54bb0fff66afdafaf51bed1fde360d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-5727-2025-ie00006.svg" width="9pt" height="16pt" src="acp-25-5727-2025-ie00006.png"/></svg:svg></span></span>) values in the SE-Dome core were <span class="inline-formula">4.2±2.8</span> ‰ lower than those in the Greenland Summit ice core between 1959 and 2006. The TRansfer of Atmospheric Nitrate Stable Isotopes To the Snow (TRANSITS) model under the SE-Dome condition estimated changes of only 0.9 ‰ for <span class="inline-formula"><i>δ</i><sup>15</sup></span>N(NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M15" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="9f81e901bf06635e082f559a787da68a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-5727-2025-ie00007.svg" width="9pt" height="16pt" src="acp-25-5727-2025-ie00007.png"/></svg:svg></span></span>) and <span class="inline-formula">−0.2</span> ‰ for <span class="inline-formula">Δ<sup>17</sup></span>O(NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M18" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="2a83a52cafded6cc529076279999d0cd"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-5727-2025-ie00008.svg" width="9pt" height="16pt" src="acp-25-5727-2025-ie00008.png"/></svg:svg></span></span>) from the initial deposition. Although differences in the source of NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M19" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="01db1dfc152077444e810c7eff7103ec"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-5727-2025-ie00009.svg" width="9pt" height="16pt" src="acp-25-5727-2025-ie00009.png"/></svg:svg></span></span> cannot be discounted, the lower <span class="inline-formula"><i>δ</i><sup>15</sup></span>N(NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M21" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="1eb1de86984802614b8a8a62ef6ea2cd"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-5727-2025-ie00010.svg" width="9pt" height="16pt" src="acp-25-5727-2025-ie00010.png"/></svg:svg></span></span>) values observed at SE-Dome compared to Summit were likely due to reduced postdepositional alteration. Therefore, the SE-Dome ice core NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M22" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="f1e19cb84feec81dda2dcfcce1dcb451"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-5727-2025-ie00011.svg" width="9pt" height="16pt" src="acp-25-5727-2025-ie00011.png"/></svg:svg></span></span> record offers a precise reconstruction of nitrogen oxides (NO<span class="inline-formula"><sub><i>x</i></sub></span>) emissions from both North America and western Europe, as well as atmospheric oxidation chemistry and transport, thereby providing reliable insight into atmospheric nitrogen cycling.</p> |
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| ISSN: | 1680-7316 1680-7324 |