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Recent studies show that the Asian summer monsoon anticyclone (ASMA) transports emissions from the rapidly industrializing nations in Asia into the tropical upper troposphere. Here, we present a unique set of measurements on over 100 air samples collected on multiple flights of the M55 Geophysica high altitude research aircraft over the Mediterranean, Nepal, and Northern India during the summers of 2016 and 2017 as part of the European Union project StratoClim. These air samples were measured for 27 ozone‐depleting substances (ODSs), many of which were enhanced above expected levels, including the chlorinated very short‐lived substances, dichloromethane (CH2Cl2), 1,2‐dichloroethane (CH2ClCH2Cl), and chloroform (CHCl3). CH2Cl2 mixing ratios in the tropopause region were 65–136 parts per trillion (ppt) in comparison to previous estimates of mixing ratios in the tropical tropopause layer of 30–44 ppt in 2013–2014. Backward trajectories, calculated with the trajectory module of the chemistry‐transport model CLaMS and driven by the ERA5 reanalysis, indicate possible source regions of CH2Cl2 in South Asia. We derived total equivalent chlorine (ECl), and equivalent effective stratospheric chlorine (EESC) and found that these quantities were substantially higher than previous estimates in the literature. EESC at mean age‐of‐air of 3 years based on the 2016 measurements was 1,861–1,872 ppt in comparison to a previously estimated EESC of 1,646 ppt. Our findings show that the ASMA transports larger than expected mixing ratios of long‐lived and very short‐lived ODSs into the upper troposphere and lower stratosphere, likely leading to an impact on the stratospheric ozone layer. Plain Language Summary: The Asian summer monsoon is an enormous weather system that occurs every summer over large parts of the Asian continent. It is known to transport emissions from the rapidly industrializing nations in East and South Asia into the tropical upper troposphere, but how much of that enters the stratosphere above is not well‐known. Here, we present a unique set of measurements on over 100 air samples collected in regions directly influenced by this monsoon system. The flights of a high altitude research aircraft took place during the summers of 2016 and 2017. These air samples were investigated for their content of ozone‐depleting substances (ODSs), which are known to be involved in the depletion of the life‐protecting stratospheric ozone layer. Many of the ODSs were enhanced above expected levels, including the particularly understudied very short‐lived chlorine‐containing compounds, dichloromethane (CH2Cl2), 1,2‐dichloroethane (CH2ClCH2Cl), and chloroform (CHCl3). An analysis of the air mass origins indicated fast transport times and source regions in South Asia. Our findings show that the Asian monsoon is transporting larger than expected mixing ratios of ODSs into the upper troposphere and lower stratosphere, likely leading to an impact on the stratospheric ozone layer. Key Points: First study to measure a comprehensive set of ozone‐depleting substances in air entering the stratosphere above the Asian summer monsoonHigher than expected mixing ratios found for many compounds, particularly chlorinated very short‐lived substancesRegional estimate but the extra equivalent chlorine could significantly enhance the chlorine and bromine loading of the entire stratosphere [ABSTRACT FROM AUTHOR]

We present the first meridional transects of atmospheric O2 and CO2 over the Atlantic Ocean. We combine these measurements into the tracer atmospheric potential oxygen (APO), which is a measure of the oceanic contribution to atmospheric O2 variations. Our new in situ measurement system, deployed on board a commercial container ship during 2015, performs as well as or better than existing similar measurement systems. The data show small short-term variability (hours to days), a step-change corresponding to the position of the Intertropical Convergence Zone (ITCZ), and seasonal cycles that vary with latitude. In contrast to data from the Pacific Ocean and to previous modeling studies, our Atlantic Ocean APO data show no significant bulge in the tropics. This difference cannot be accounted for by interannual variability in the position of the ITCZ or the Atlantic Meridional Mode Index and appears to be a persistent feature of the Atlantic Ocean system. Modeled APO using the TM3 atmospheric transport model does exhibit a significant bulge over the Atlantic and overestimates the interhemispheric gradient in APO over the Atlantic Ocean. These results indicate that either there are inaccuracies in the oceanic flux data products in the equatorial Atlantic Ocean region, or that there are atmospheric transport inaccuracies in the model, or a combination of both. Our shipboard O2 and CO2 measurements are ongoing and will reveal the long-term nature of equatorial APO outgassing over the Atlantic as more data become available. [ABSTRACT FROM AUTHOR]