Ozone dry deposition to the sea surface microlayer

Tropospheric ozone is a significant climate gas and has a major influence on air quality, public health, and food security. Ozone is lost to the Earth’s surface directly by “dry deposition”, which is an important loss process for this gas. Since the ocean represents 70% of the surface, uncertainties in the dry deposition to the “sea surface microlayer” (SML) of the ocean translate into large differences in the predicted global ocean dry deposition flux. There has been very limited experimental quantification of ozone deposition over the oceans, because making such measurements is technically very challenging, and estimates of oceanic ozone deposition velocities vary widely. The mechanistic details of the process are incomplete and parameterisations in models are untested against observations. This loss of ozone is acknowledged to be controlled predominantly by chemical reactions in the SML involving iodide and organic material, which not only determine how quickly ozone can be irreversibly taken up at the ocean surface, but may also constitute a source of trace gases to the marine atmosphere. Whilst there is a growing body of work on ozone interactions with oceanic iodide, the nature and reactivity of the organic material in the SML which interacts with ozone is completely unknown. This project will probe both the fundamental mechanisms on and in the SML involved in the loss of ozone and production of atmospherically important trace gases and, in a highly novel and agenda-setting approach, apply this mechanistic information to field observations of oceanic ozone fluxes and the corresponding biogeochemical properties of the SML. This highly interdisciplinary study involves aspects of physical chemistry, atmospheric chemistry, ocean chemistry and physics, and engineering. It transcends conventional boundaries by integrating across atmospheric and ocean science, reflecting the PIs world-leading expertise in field and laboratory science in these fields.