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 (Tw) range between 1C and 15C. A sharp decrease in PMA emissions for a Tw increase from 1C to 4C was followed by a lower rate of change in PMA emissions for Tw up to about 6C. Near constant number concentrations for water temperatures between 6C to 10C and higher were recorded. Even though the total particle number concentration changes for overlapping Tw 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 (DpDp 0.125m, 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 Tw from 1C to 10C during winter measurements showed a decrease in the peak of relative particle number concentration at about a Dp of 0.180m, while an increase was observed for particles with Dp 1m. Summer measurements exhibited a relative shift to smaller particle sizes for an increase of Tw in the range 7–11C. The differences in the shape of the number size distributions between winter and summer may be caused by different production of organic material in water, different local processes modifying the water masses within the fjord (for example sea ice production in winter and increased glacial meltwater inflow during summer) and different origin of the dominant sea water mass. Further research is needed regarding the contribution of these factors to the PMA production.
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