Analytical Chemistry Seminar: Dr. Susan Tegtmeier
Jointly sponsored by the Department of Chemistry and Biochemistry, CIRES, and the Environmental Program
The Role of Oceanic Halogen and Sulfur Compounds for the Middle Atmosphere
Dr. Susan Tegtmeier
GEOMAR Helmholtz Centre for Ocean Research Kiel
The decline of anthropogenic chlorine in the stratosphere within the 21st century will increase the relative importance of naturally emitted, very short lived halocarbons on stratospheric ozone destruction. Such halocarbons play a significant role in present day ozone depletion, in particular in combination with enhanced stratospheric sulfate aerosol loading. There is a need to better understand how much of the observed stratospheric halogen and sulfur aerosol originates from natural sources, in particular from oceanic emissions, and how this will change and affect the middle atmosphere in a future climate.
In this talk, I will describe recent advances in our understanding of brominated and iodinated halocarbons based on ship campaign data, modelling studies, and aircraft measurements, including current and future halocarbon emission inventories and their contribution to the stratospheric halogen loading. Similarly, dimethylsulphide emissions are used to assess the impact of naturally emitted sulfur on the stratospheric aerosol loading. One focus of the presentation is on the tropical West Pacific, the main source region for stratospheric air, where highly localized halogen sources and a tropospheric OH minimum were identified. The potential of the latter to amplify the impact of oceanic halocarbons and South East Asian SO2 on the stratospheric composition is discussed. Finally, the ozone-depletion potential weighted emissions of halocarbons will be compared to those of other ozone depleting substances to quantify the overall impact of natural halocarbons on the ozone layer for current day conditions and future scenarios.