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Primary marine aerosols (PMAs) are an important source of cloud condensation nuclei, and one of the key elements of the remote marine radiative budget. Changes occurring in the rapidly warming Arctic, most importantly the decreasing sea ice extent, will alter PMA production and hence the Arctic climate through a set of feedback processes. In light of this, laboratory experiments with Arctic Ocean water during both Arctic winter and summer were conducted and focused on PMA emissions as a function of season and water properties. Total particle number concentrations and particle number size distributions were used to characterize the PMA population. A comprehensive data set from the Arctic summer and winter showed a decrease in PMA concentrations for the covered water temperature (T-w) range between - 1 degrees C and 15 degrees C. A sharp decrease in PMA emissions for a T-w increase from -1 degrees C to 4 degrees C was followed by a lower rate of change in PMA emissions for T-w up to about 6 degrees C. Near constant number concentrations for water temperatures between 6 degrees C to 10 degrees C and higher were recorded. Even though the total particle number concentration changes for overlapping T-w ranges were consistent between the summer and winter measurements, the distribution of particle number concentrations among the different sizes varied between the seasons. Median particle number concentrations for a dry diameter (D-p) < 0.125 mu m measured during winter conditions were similar (deviation of up to 3 %), or lower (up to 70 %) than the ones measured during summer conditions (for the same water temperature range). For D-p > 0.125 mu m, the particle number concentrations during winter were mostly higher than in summer (up to 50 %). The normalized particle number size distribution as a function of water temperature was examined for both winter and summer measurements. An increase in T-w from -1 degrees C to 10 degrees C during winter measurements showed a d

Sea spray aerosols are an important part of the climate system through their direct and indirect effects. Due to the diminishing sea ice, the Arctic Ocean is one of the most rapidly changing sea spray aerosol source areas. However, the influence of these changes on primary particle production is not known. In laboratory experiments we examined the influence of Arctic Ocean water temperature, salinity, and oxygen saturation on primary particle concentration characteristics. Sea water temperature was identified as the most important of these parameters. A strong decrease in sea spray aerosol production with increasing water temperature was observed for water temperatures between -1 degrees C and 9 degrees C. Aerosol number concentrations decreased from at least 1400 cm(-3) to 350 cm-3. In general, the aerosol number size distribution exhibited a robust shape with one mode close to dry diameter D-p 0.2 mu m with approximately 45% of particles at smaller sizes. Changes in sea water temperature did not result in pronounced change of the shape of the aerosol size distribution, only in the magnitude of the concentrations. Our experiments indicate that changes in aerosol emissions are most likely linked to changes of the physical properties of sea water at low temperatures. The observed strong dependence of sea spray aerosol concentrations on sea water temperature, with a large fraction of the emitted particles in the typical cloud condensation nuclei size range, provide strong arguments for a more careful consideration of this effect in climate models.