Primary Marine Aerosol Production : An experimental study based on Arctic Ocean water and a sea water proxy

Abstract: This thesis focuses on the interplay between the physical properties of ocean water and primary marine aerosol (PMA) emissions in the context of a rapidly changing Arctic climate. PMAs are an important part of the climate system due to their ability to interact with incoming solar radiation and to influence cloud properties. The rapid changes taking place in the Arctic emphasize the need for an increased understanding of the feedback processes in the ocean-atmosphere-climate system. Less sea ice cover in a warmer climate results in a larger area for PMA emissions, but little is known about the impact of changes in water properties on PMA emissions.This thesis examines the influence of water temperature (Tw), salinity, oxygen saturation, and organic content on PMA characteristics (particle number concentration, number size distribution, and light absorption) based on laboratory experiments with Arctic Ocean water and a sea water proxy.Increasing Tw from about 0 °C up to about 7–10 °C results in a decrease by up to a factor of ten in particle number concentration. Concurrently, the particle light absorbing efficiency decreases by about 3 to 5 times. For a change in Tw above 7–10 °C, no impact on particle number concentration was detected. A shift towards larger sizes with an increase in Tw was observed for wintertime PMA size distributions, whilst a shift towards smaller sizes was observed for PMA size distributions based on Arctic Ocean water sampled during summertime. Changes in salinity and oxygen saturation did not show a significant impact on the examined aerosol properties. The temperature dependent trend in PMA emissions was confirmed by laboratory experiments with a simple sea water proxy using a NaCl solution with varying salinities and organic content (succinic acid). The results from this thesis deliver fundamental knowledge for a better assessment of ocean-aerosol-cloud interaction feedbacks in a future warmer Arctic.