Comparative analysis of tropospheric ozone concentrations at Union Glacier, Antarctica: long-term observations and recent measurements
Authors: Díaz Robles Luis Alonso , Vallejo Gallardo Fidel , Campos Bravo Valeria , Fadic Ximena , Barcaza Gonzalo , Moosmuller Hans , Cereceda-Balic Francisco 
Published: March 2024

This study compares tropospheric ozone (O3) concentrations measured at Union Glacier (UG), Antarctica, in December 2023 with long-term trends and observations reported in recent literature. Ground-measurements for continuous gas and particulate matter monitoring were carried out at UG (West Antarctica), nearby the Estaci&#243;n Polar Conjunta Glaciar Uni&#243;n (79&#176; 46&#180;S 82&#176; 19&#180;W). Union Glacier, which with ~2561 km2, is one of the largest outlet glaciers in the Ellsworth Mountains, flowing to the Ronne-Filchner Ice Shelf. Ozone concentrations were measured using an ETL-ONE multiparametric air quality monitoring station equipped with an UniTec SENS-IT O3 metal oxide sensor, which shows strong correlation with the Federal Reference Methods (FRMs) for O3, for both field (R2 ~ 0.72-0.83) and laboratory studies (R2 >0.80 ). During over one week of monitoring with 1-minute resolution, we observed high O3 levels at UG (mean: 45.8 ppb), significantly exceeding typical polar values. These findings are juxtaposed with analyses from various studies spanning over two decades, offering a broader context of O3 dynamics in polar regions.Kumar et al. (2021) and Helmig et al. (2007) documented increasing surface O3 trends in Antarctica, associating them with climate issues and radiative processes. Our observations at UG align with these increasing trends but notably surpass the projected mean values, suggesting additional local or transient factors influencing O3 levels. As observed in our study, the possible intrusion of stratospheric O3 resonates with Yan Xia et al. (2023) findings, emphasizing the impact of stratospheric-tropospheric exchange, particularly during sudden stratospheric warming events.Furthermore, the subtle yet persistent O3 increases noted by Law et al. (2023) in the Arctic provide a comparative baseline, highlighting the polar-specific atmospheric dynamics. Our data also contribute to understanding the complex interplay of O3 with nitrogen oxides (NOx), as discussed by Zhou et al. (2020), indicating that background NOx might play a crucial role in O3 variability.In light of these comparative analyses, our study underscores the importance of continued and enhanced O3 monitoring in Antarctica to decipher the underlying mechanisms driving its distribution. These findings are particularly crucial for predicting future climate impacts and understanding the role of polar regions in global atmospheric chemistry. They advocate for a more nuanced understanding of polar O3 trends, factoring in localized events and broader climatic influences to elucidate the evolving narrative of tropospheric O3 in these remote regions.Acknowledgment to INACH Project RT_34-21 and ANID Proyect: Anillo ACONCAGUA ACT210021, Fondecyt Regular 1221526 and FOVI230167.References:Helmig et al. (2007)Kumar et al. (2021)Law et al. (2023)Yan Xia et al. (2023)Zhou et al. (2020)