Atmosphere-ocean interactions play a key role in regulating atmospheric composition and climate. We study the controls and mechanisms responsible for the release of a wide range of oceanic trace gases, with a focus on volatile halogens and their influence on atmospheric chemistry. The photo dissociation of reactive halogens initiates a complex series of atmospheric reactions that can deplete ozone and lead to the formation of fine aerosol in the lower atmosphere. Potential mechanisms for release of halogens to the atmosphere, and their effects on surface ozone have been demonstrated in a series of laboratory and field experiments. Relatively stable organic halogens emitted from the oceans can be transported to the lower stratosphere and make a significant contribution there to total bromine levels and thus to stratospheric ozone depletion. Within the CAST/ATTREX project in collaboration with US partners we measured short-lived bromine compounds from research aircraft to improve understanding of the tropical atmosphere and how gases move from the surface to the stratosphere. Within the NERC-funded ACCACIA project we are studying Arctic emissions of oceanic gases like dimethylsulfide (DMS) in order to better understand Arctic cloud and aerosol processes. We are also interested in how low volatility organic compounds are formed in the marine atmosphere and are studying sources of oceanic isoprene and monoterpenes within the ORC3 project.
Most of our research involves field work to directly probe the atmosphere; we deploy our instruments on ship, ground-based and airborne platforms. Experimental techniques for both laboratory and field research include thermal desorption (TD)-GC-MS (both EI and CI, with fast GC), LC-ion trapMS, PTR-ToF and UV-vis spectroscopy. We have set up and now run the Cape Verde Atmospheric Observatory (CVAO) in the tropical east Atlantic: this is now a global WMO/GAW monitoring station and plays a key role in global monitoring of the tropical atmosphere.
Impact of oceanic emissions on atmospheric oxidation and climate