Potential impact of ocean ecosystem changes due to global warming on marine organic carbon aerosols

Production of organic carbon (OC) aerosols by biological activity in the ocean is hypothesized to influence climate change. We employ model sensitivity studies to assess the effects of ocean ecosystem changes on the marine OC fluxes by using an integrated Earth system model. Our modeled estimate of global marine primary OC emission (7 Tg OC yr(-1)) is comparable with that calculated from sensitivity simulation which uses chlorophyll concentration constrained by the satellite observations. The model significantly underestimates OC concentration in summer over the remote ocean without the ocean source, but better agreement could be achieved by adding the marine source. We apply simulated perturbations in chlorophyll concentration and the sea-ice extent by previous model run for the IPCC AR4 to the OC source function only. Our model results suggest an insignificant change in the global mean primary OC flux from the ocean to the atmosphere but with considerably large spatial variability due to the changes in chlorophyll concentration projected by the climate warming simulation. The major features of the geographical distribution are increases over the Arctic Ocean, which are associated with the chlorophyll concentration and the sea-ice extent changes primarily driven by the enhanced light efficiency for photosynthesis in the sea-ice free ocean. In climate chemistry and aerosol models that ignore this process, the future (late 21st century) surface OC concentration would be underestimated by 40-200 ng m(-3) in September over the Arctic Ocean (70-90 degrees N).