Pelagic ecosystem emissions of aerosol-forming substances in Antarctica and the Subantarctic

2018 Ocean Sciences Meeting, 11-16 February, in Portland, Oregon
Climate warming affects the development and distribution of sea ice south of the Polar Front around Antarctica and its associated ecosystems, but at present the evidence of feedbacks on climate through ecosystem-derived changes in the atmosphere is sparse. The PEGASO cruise visited the Antarctic region of the South Orkney Islands at the northern edge of the Weddell Sea, and the Subantarctic region of the South Georgia Island, in summer 2015. Each region was studied intensively in lagrangian mode over a few days and diel cycles. Oceanic measurements of plankton abundance, diversity, activity and physiology, plus organic matter characteristics, organic volatile compounds (dimethylsulfide, isoprene, halomethanes) and nutrient concentrations, were compared with simultaneous atmospheric measurements of aerosol numbers, size and composition. Samples of surface seawater and melted sea ice were bubbled in an aerosol-generation tank and the characteristics of the sprayed aerosol were monitored. This integrated study allowed to link phytoplankton bloom stages and the emission of aerosol-forming particulate and gaseous substances. For instance, we observed that the microbiota of sea ice and sea ice-influenced ocean are a previously unknown significant source of atmospheric organic nitrogen, including low molecular weight alkyl-amines. Given the keystone role of nitrogen, sulfur, carbon and iodine compounds in aerosol formation, growth and neutralization, our findings call for greater chemical and source diversity in the modeling efforts linking the marine ecosystem to aerosol-mediated climate effects in the Southern Ocean