A quantitative understanding of atmospheric Cl and of the Mineral Dust-Sea spray Aerosols (MDSA) mechanism is however inhibited by a lack of field observations.

Key goals:

• Quantitatively evaluate the drivers of Cl production through field observations of speciated chlorine at the Cape Verde Observatory (CVO)
• Robustly evaluate indirect field evidence for Cl enhancement
• Determine whether the natural Cl sink of methane via the MDSA mechanism is effective
• Improve knowledge of the potential impact of enhanced Cl levels from MDSA chemistry on methane, climate and air quality

CEMDEM-CVO will provide direct evidence of the importance of the MDSA mechanism for methane lifetime in the present day atmosphere and provide quantitative observations in the marine boundary layer (MBL) needed for validating its incorporation in models. The dataset and understanding gained will represent a significant advancement in quantifying the true impact of chlorine as a global methane sink and the sensitivities of this chemistry to aerosol and trace gas composition. The knowledge on the impacts from this study will not only be applicable in the Atlantic, but will also be used to quantify methane oxidation by chlorine in other parts of the world that are affected by MDSA. The project also has the potential to form the basis of climate intervention studies for increased chlorine emission leading to methane destruction.

‍