AS2.6

Air-sea Chemical Fluxes: Impacts on Biogeochemistry and Climate
Convener: Maria Kanakidou | Co-conveners: Parvadha Suntharalingam, Akinori Ito, Robert Duce, Cécile Guieu

Ocean-atmosphere flux exchanges of biogeochemically active constituents have significant impacts on global biogeochemistry and climate. Increasing atmospheric deposition of anthropogenically-derived nutrients (e.g., nitrogen, phosphorus, iron) to the ocean influences marine productivity and has associated impacts on oceanic CO2 uptake, and emissions to the atmosphere of climate active species (e.g., nitrous-oxide (N2O), dimethyl-sulfide (DMS), marine organic compounds and halogenated species). Atmospheric inputs of toxic substances (e.g., lead, mercury, cadmium, copper, persistent organic pollutants) into the ocean are also of concern for their impact on ocean ecosystem health. In recent decades the intensive use of plastics has led to significant levels of persistent micro- and nano- plastics being transported into the marine atmosphere and to the ocean, with considerable uncertainty remaining on transport pathways and oceanic impacts. Other influential recent changes include emission reductions for air pollution abatement which have resulted in changes in cloud and aerosol chemical composition, affecting atmospheric acidity, associated chemical processing and impacts via atmospheric deposition on ocean biogeochemistry.

In turn, oceanic emissions of reactive species and greenhouse gases influence atmospheric chemistry and global climate, and induce potentially important chemistry-climate feedbacks. While advances have been made by laboratory, field, and modelling studies over the past decade, we still lack understanding of many of the physical and biogeochemical processes linking atmospheric deposition of chemicals, nutrient availability, marine biological productivity, trace-gas sources and sinks and the biogeochemical cycles governing air-sea fluxes of these climate active species, as well as on the atmosphere-ocean cycle of microplastics and its impact on the environment and climate.
This session will address the above issues on the atmospheric deposition of nutrients and toxic substances to the ocean, the impacts on ocean biogeochemistry, and also the ocean to atmosphere fluxes of climate active species and potential feedbacks to climate. We welcome new findings from measurement programmes (laboratory, in-situ and remote sensing) and atmospheric and oceanic numerical models.
This session is jointly sponsored by GESAMP Working Group 38 on ‘The Atmospheric Input of Chemicals to the Ocean’ and the Surface Ocean-Lower Atmosphere Study (SOLAS).