Aerosols scatter sun light and act as Cloud Condensation Nucleus (CCN), which cause the most uncertain man-made climate forcing. Sea spray aerosols (SSA) are the largest natural aerosol source. SSA emissions are driven by wind, water temperature, sea ice, salinity and marine micro-biology, all which are influenced by climate change, causing feed-back loops. We have got a fair grip on how physical factors influence the SSA sea salt part but are largely in the dark on the organic and biological fractions, and on the influence of salinity and biology. To quantify in situ emissions, we will use Eddy C ovariance (EC ) fluxes. EC requires
very fast sensors, which makes it impossible to characterise chemistry, microbiology and CCN-properties at the same time. Instead this will be done in a SSA simulation tank. We have previously successfully applied both methods separately. Applying both simultaneously, with water from the flux-foot-print in the tank, kept at in situ temperature, will give both characterisation and quantification. We will arrange two campaigns at an ICOS-station in the Baltic Sea, where we have unique multiple year EC -aerosol-fluxes. We seek colaboration for an opprotunity to participate in one cruise in the Atlantic/Arctic/Pacific/Indian oceans (with ordinary salinity). We will derive source parameterizations for the organic SSA, the effect of salinity, and enrichment factors for micro-organisms, and apply these in a climate model (Nor-ESM). The climate forcing and feed-back by SSA will be derived from simulations of present and future climate.