Shipborne observations reveal contrasting Arctic marine, Arctic terrestrial and Pacific marine aerosol properties

Abstract

pThere are few shipborne observations addressing the factors influencing the relationships of the formation and growth of aerosol particles with cloud condensation nuclei (CCN) in remote marine environments. In this study, the physical properties of aerosol particles throughout the Arctic Ocean and Pacific Ocean were measured aboard the Korean icebreaker R/V iAraon/i during the summer of 2017 for 25 d. A number of new particle formation (NPF) events and growth were frequently observed in both Arctic terrestrial and Arctic marine air masses. By striking contrast, NPF events were not detected in Pacific marine air masses. Three major aerosol categories are therefore discussed: (1) Arctic marine (aerosol number concentration CNspan classCombining double low line"inline-formula"2.5/span: span classCombining double low line"inline-formula"413±442/span cmspan classCombining double low line"inline-formula"-3/span), (2) Arctic terrestrial (CNspan classCombining double low line"inline-formula"2.5/span: span classCombining double low line"inline-formula"1622±1450/span cmspan classCombining double low line"inline-formula"-3/span) and (3) Pacific marine (CNspan classCombining double low line"inline-formula"2.5/span: span classCombining double low line"inline-formula"397±185/span cmspan classCombining double low line"inline-formula"-3/span), following air mass back-trajectory analysis. A major conclusion of this study is not only that the Arctic Ocean is a major source of secondary aerosol formation relative to the Pacific Ocean but also that open-ocean sympagic and terrestrially influenced coastal ecosystems both contribute to shaping aerosol size distributions. We suggest that terrestrial ecosystems-including river outflows and tundra-strongly affect aerosol emissions in the Arctic coastal areas, possibly more than anthropogenic Arctic emissions. The increased river discharge, tundra emissions and melting sea ice should be considered in future Arctic atmospheric composition and climate simulations. The average CCN concentrations at a supersaturation ratios of 0.4 % were span classCombining double low line"inline-formula"35±40/span cmspan classCombining double low line"inline-formula"-3/span, span classCombining double low line"inline-formula"71±47/span cmspan classCombining double low line"inline-formula"-3/span and span classCombining double low line"inline-formula"204±87/span cmspan classCombining double low line"inline-formula"-3/span for Arctic marine, Arctic terrestrial and Pacific marine aerosol categories, respectively. Our results aim to help evaluate how anthropogenic and natural atmospheric sources and processes affect the aerosol composition and cloud properties.