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Sensitivity results of the modeled isotopes, i.e., δ15N(NO3-) (a) and Δ17O(NO3-) (b), to TCO and snow accumulation rate. Gray curve: ice-core observed record; Red curve: modeled results with observed accumulation rate and TCO; Green curve: modeled results with observed TCO but mean accumulation rate throughout the record; Blue curve: modeled results with observed accumulation rate but TCO was kept the same before and after 1976. Gray area represents the ozone hole period.
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Column ozone variability has important implications for surface photochemistry and the climate. Ice-core nitrate isotopes are suspected to be influenced by column ozone variability and δ15N(NO3-) has been sought to serve as a proxy of column ozone variability. In this study, we examined the ability of ice-core nitrate isotopes to reflect column ozo...
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The Antarctic ozone hole has attracted attention concerning global climate change. Breakthroughs regarding ozone observation methods and the formation principles of ozone holes have occurred. This study compared the slant column ozone obtained from SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) Level 1 optical spe...
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... The stable isotope of nitrogen 15 N in NO − 3 (δ 15 N(NO − 3 )) in surface snow is highly enriched compared to atmospheric NO − 3 (e.g. Erbland et al., 2013;Cao et al., 2022;Winton et al., 2020) due to NO − 3 loss and redistribution from snow, which is driven by UV photolysis (Frey et al., 2009;Berhanu et al., 2014;Shi et al., 2019). NO − 3 isotopic fractionation is strongest at sites with very low snow accumulation rates (2-3 cm a −1 (w.e.)), such as Dome A and Dome C on the East Antarctic Plateau, due to enhanced NO − 3 post-depositional recycling which erases the source signature of δ 15 N(NO − 3 ) due to longer exposure of surface snow layers to incoming UV radiation before burial (Shi et al., 2022a;Frey et al., 2009). ...
... NO − 3 isotopic fractionation is strongest at sites with very low snow accumulation rates (2-3 cm a −1 (w.e.)), such as Dome A and Dome C on the East Antarctic Plateau, due to enhanced NO − 3 post-depositional recycling which erases the source signature of δ 15 N(NO − 3 ) due to longer exposure of surface snow layers to incoming UV radiation before burial (Shi et al., 2022a;Frey et al., 2009). Higher rates of snow accumulation rate to 6 cm a −1 (w.e.) and above is sufficient to preserve the seasonal cycle of δ 15 N(NO − 3 ) in the snowpack (Winton et al., 2020), and enrichments in δ 15 N(NO − 3 ) by the effects of snow accumulation superimpose those due to stratospheric ozone depletion (Cao et al., 2022;Shi et al., 2022b). The inverse relationship between the snow accumulation rate and δ 15 N(NO − 3 ) is well constrained across Antarctica so that for ice core sites within the transition zones between the dome summits and the coast with a snow accumulation rate between 4 and 20 cm a −1 (w.e.), ice core δ 15 N(NO − 3 ) has been proposed as proxy for surface mass balance (Akers et al., 2022). ...
Within the framework of the Isotopic Constraints on Past Ozone Layer in Polar Ice (ISOL-ICE) project, we present initial ice core results from the new ISOL-ICE ice core covering the last millennium from high-elevation Dronning Maud Land (DML) and discuss the implications for interpreting the stable isotopic composition of nitrogen in ice core nitrate (δ15N(NO3-)) as a surface ultra-violet radiation (UV) and total column ozone (TCO) proxy. In the quest to derive TCO using δ15N(NO3-), an understanding of past snow accumulation changes, as well as aerosol source regions and present-day drivers of their variability, is required. We therefore report here the ice core age–depth model, the snow accumulation and ice chemistry records, and correlation analysis of these records with climate variables over the observational era (1979–2016). The ISOL-ICE ice core covers the last 1349 years from 668 to 2017 CE ± 3 years, extending previous ice core records from the region by 2 decades towards the present and shows excellent reproducibility with those records. The extended ISOL-ICE record of last 2 decades showed a continuation of the methane sulfonate (MSA-) increase from ∼ 1800 to present while there were less frequent large deposition events of sea salts relative to the last millennium. While our chemical data do not allow us to distinguish the ultimate (sea ice or the open ocean) source of sea salt aerosols in DML winter aerosol, our correlation analysis clearly suggests that it is mainly the variability in atmospheric transport and not the sea ice extent that explains the interannual variability in sea salt concentrations in DML. Correlation of the snow accumulation record with climate variables over the observational era showed that precipitation at ISOL-ICE is predominately derived from the South Atlantic with onshore winds delivering marine air masses to the site. The snow accumulation rate was stable over the last millennium with no notable trends over the last 2 decades relative to the last millennium. Interannual variability in the accumulation record, ranging between 2 and 20 cm a-1 (w.e.), would influence the ice core δ15N(NO3-) record. The mean snow accumulation rate of 6.5±2.4 cm a-1 (w.e.) falls within the range suitable for reconstructing surface mass balance from ice core δ15N(NO3-), highlighting that the ISOL-ICE ice core δ15N(NO3-) can be used to reconstruct either the surface mass balance or surface UV if the ice core δ15N(NO3-) is corrected for the snow accumulation influence, thereby leaving the UV imprint in the δ15N(NO3-) ice core record to quantify natural ozone variability.
... NO3isotopic fractionation is strongest at sites with very low snow accumulation rates (2-3 cm a -1 (w.e.), such as Dome A and Dome C on the East Antarctic Plateau, due to enhanced NO3post-depositional recycling which erases the source signature of δ 15 N(NO3 -) due to longer exposure of surface snow layers to incoming UV radiation before burial (Shi et al., 2022a;Frey et al., 2009). Increases of snow accumulation rate to 6 cm a -1 (w.e.) and above 50 is sufficient to preserve the seasonal cycle of δ 15 N(NO3 -) in the snowpack and enrichments in δ 15 N(NO3 -) by the effects of snow accumulation superimpose those due to stratospheric ozone depletion (Cao et al., 2022;Shi et al., 2022b). The inverse relationship between the snow accumulation rate and δ 15 N(NO3 -) is well constrained across Antarctica so that for ice core sites within the transition zones between the dome summits and the coast with a snow accumulation rate between 4 and 20 cm a -1 (w.e.), ice core δ 15 N(NO3 -) has been proposed as proxy for surface mass balance (Akers et al., 2022b). ...
... While previous studies found that MSA variability in the high-elevation DML region was associated with transport strength rather the sea ice conditions (Fundel et al., 2006;Abram et al., 2007), we investigated whether the additional two decades of MSA ice core data from ISOL-ICE captures local sea ice changes. Recently, Isaacs et al. (2021) and Clem et al. (2018) found that over the period 1979-2018, ENSO impacted summer and autumn sea ice concentration around coastal DML (10-70°E) 400 ...
Quantifying the natural variability of the stratospheric ozone layer and understanding the underlying factors that control natural total column ozone (TCO) variability are required to put modern observations into historical context and evaluate the effectiveness of climate and TCO protection policies. Within the framework of the Isotopic Constraints on Past Ozone Layer in Polar Ice (ISOL-ICE) project, we present initial ice core results from the new ISOL-ICE ice core covering the last millennium from the high-elevation Dronning Maud Land (DML) located under the Antarctic spring stratospheric TCO minimum, and discuss the implications for interpreting the stable isotopic composition of nitrogen in ice core nitrate (δ15N(NO3-)) as a surface ultra-violet radiation (UV) and TCO proxy. To interpret the ice core δ15N(NO3-) record, an understanding of past snow accumulation changes, as well as aerosol source regions and present-day drivers of their variability are required. We therefore report here the ice core age-depth model, the snow accumulation and ice chemistry records, and correlation analysis of these records with climate variables over the observational era (1979–2016). The ISOL-ICE ice core covers the last 1349 years from 668 to 2017 C.E. ± 3 years extending previous ice core records from the region by two decades and shows excellent reproducibility with those records. The extended ISOL-ICE record of last two decades showed a continuation of the methanesulphonate (MSA) increase from ~1800 to present while there were less frequent large deposition events of sea salts relative to the last millennium. The correlation analysis, combined with the finding that sea salts do not carry a sea ice signature to the site, highlight that sea salt and MSA aerosol concentrations are primarily related to atmospheric transport over the extended two-decade period and not to changes in sea ice source strength. Correlation of the snow accumulation record with climate variables over the observational era showed that precipitation at ISOL-ICE is predominately derived from the South Atlantic with onshore winds delivering marine air masses to the site. The snow accumulation rate was stable over the last millennium with no notable trends over last two decades relative to the last millennium. Interannual variability in the accumulation record, ranging between 2 and 20 cm a−1 (w.e.), would influence the ice core δ15N(NO3-) record. The mean snow accumulation rate of 6.5 ± 2.4 cm a-1 (w.e.) falls within the range suitable for reconstructing surface mass balance from ice core δ15N(NO3-) highlighting that the ISOL-ICE ice core δ15N(NO3-) can be used to reconstruct either the snow accumulation rate or surface UV if the ice core δ15N(NO3-) is corrected for the snow accumulation influence.
... The isolated Antarctic continent is ideal for studying natural atmospheric variability thanks to its remoteness from anthropogenic pollution sources that can confound the investigation of natural variability compared to more populated regions (Shaw 1982;Cao et al. 2022;Marina-Montes et al. 2022). Antarctic ice cores are valuable for reconstructing the past climate because they can provide sub-annually resolved, continuous proxy records over thousands of years (Mayewski et al. 1995;Alley 2014;Strugnell et al. 2022;Jones et al. 2023). ...
The study investigates a shallow ice core (IND–25/B5) drilled near Humboldt Mountain in Dronning Maud Land (DML) region, during the 25th Indian Antarctic Expedition (2005-2006), to understand the variability in microparticle input to the region, and their characterization under the Scanning Electron Microscope-Electron Dispersive Spectroscopy (SEM-EDS). Also, the volcanic chronology of the ice core was established using the presence of volcanic shards at various depths of the ice core. The results suggest that the dust input to the study area has drastically increased since 1980, indicating changes in the atmospheric circulation pattern, local environmental conditions, increased global aridity and/or expansion of the ice-free oasis in the DML region. Silica (Volcanic and Mineral dust), Carbon (Calcareous and Organic) and other microparticles are three major types of particles observed in the ice core. Volcanic ash microparticles are observed at various depths, which depict glassy structures with conchoidal fractures and high SiO2 concentrations (>50%). The major volcanic events traced include Krakatoa, Indonesia (2001); Mount Pinatubo, Phillipines (1991); Mount Agung, Indonesia (1963) and Cerro Azul, Chile (1916-1929).
... Photolytic impacts, in particular, are sensitive to SMB in East Antarctica with a strong linear correlation observed spatially between δ 15 N NO 3 and the reciprocal SMB (Akers et al., 2022b). Changes in insolation, total column ozone, and snow optical properties also can leave imprints on the isotopic values of NO − 3 by affecting the photolytic rate, but the greater photolytic sensitivity to SMB changes tends to overwhelm and obscure their impact (Zatko et al., 2016;Winton et al., 2020;Akers et al., 2022b;Cao et al., 2022;Shi et al., 2022b). Still, these other photolytic factors remain enticing targets for paleoenvironmental reconstruction. ...
... Coupled with physical measurements of the ice core's volume and mass, we can model SMB based on physical changes in ice density and/or annual layer thickness (e.g., Fudge et al., 2016;Akers et al., 2022b). This physical SMB reconstruction could then be used to remove the SMB signal from a parallel NO − 3 isotope record, and the residual NO − 3 isotopic variability should reflect past changes in other environmental factors, such as insolation, total column ozone, snow optical properties, and atmospheric NO − 3 sourcing and chemistry (Zatko et al., 2016;Cao et al., 2022;Shi et al., 2022b). This would be most ef-fective for δ 15 N NO 3 which has a more clear relationship with SMB (Akers et al., 2022b) than δ 18 O NO 3 or 17 O NO 3 , but additional investigation into the mechanisms behind the apparent impacts of photolysis on oxygen isotopic composition is likely to provide valuable insight into past and present NO − 3 dynamics as well. ...
Nitrate in Antarctic snow has seasonal cycles in 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 an 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 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 in similar transitional regions will remain 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.
Nitrate is an important component of PM2.5, and its dry deposition and wet deposition can have an impact on ecosystems. Nitrate in the atmosphere is mainly transformed by nitrogen oxides (NOX = NO + NO2) through a number of photochemical processes. For effective management of the atmosphere’s environment, it is crucial to understand the sources of atmospheric NOX and the processes that produce atmospheric nitrate. The stable isotope method is an effective analytical method for exploring the sources of NO3⁻ in the atmosphere. This study discusses the range and causes of δ¹⁵N data from various sources of NOX emissions, provides the concepts of stable isotope techniques applied to NOX traceability, and introduces the use of Bayesian mixture models for the investigation of NOX sources. The combined application of δ¹⁵N and δ¹⁸O to determine the pathways of nitrate formation is summarized, and the contribution of Δ¹⁷O to the atmospheric nitrate formation pathway and the progress of combining Δ¹⁷O simulations to reveal the atmospheric oxidation characteristics of different regions are discussed, respectively. This paper highlights the application results and development trend of stable isotope techniques in nitrate traceability, discusses the advantages and disadvantages of stable isotope techniques in atmospheric NOX traceability, and looks forward to its future application in atmospheric nitrate pollution. The research results could provide data support for regional air pollution control measures.
