Halocarbons in the Bay of Bengal to the atmosphere

durch Birgit Quack (GEOMAR)

Mittwoch 19.11.2025, 13:15 → 14:30 Europe/Berlin

Abstract:

Halocarbons from the ocean, such as the short-lived bromoform (CHBr₃), the largest organic bromine source for the atmosphere, dibromo­methane (CH₂Br₂) and methyl iodide (CH₃I), contribute to ozone depletion in the troposphere and stratosphere. Dichloromethane (CH₂Cl₂) and chloroform (CHCl₃) with increasing anthropogenic emissions gain importance for stratospheric ozone-depletion. Especially in the tropics, rapid photolysis releases iodine into the marine boundary layer and fast vertical transport can supply the brominated and chlorinated compounds to the stratosphere. Biological, chemical and physical transport processes shape the halocarbon distributions in the ocean and their marine emissions. We report on sources and air- sea fluxes of eleven major halocarbons with different lifetimes in ocean and atmosphere from the expedition SO305 into the Bay of Bengal in April/May 2024, and show that the Bay of Bengal is a constant source of all compounds to the atmosphere in spring intermonsoon with different contributions to the atmosphere.