Abstract
A clear understanding of new particle formation processes in remote oceans is critical for properly assessing the role of oceanic dimethyl sulfide (DMS) emission on the Earth’s climate and associated climate feedback processes. Almost free from anthropogenic pollutants and leafed plants, the Antarctic continent and surrounding oceans are unique regions for studying the lifecycle of natural sulfate aerosols. Here we investigate the well-recognized seasonal variations of new particle formation around Antarctic coastal areas with a recently developed global size-resolved aerosol model. Our simulations indicate that enhanced DMS emission and photochemistry during the austral summer season lead to significant new particle formation via ion-mediated nucleation (IMN) and much higher particle number concentrations over Antarctica and surrounding oceans. By comparing predicted condensation nuclei larger than 10 nm (CN10) during a three-year period (2005–2007) with the long-period continuous CN10 measurements at the German Antarctic station Neumayer, we show that the model captures the absolute values of monthly mean CN10 (within a factor 2–3) as well as their seasonal variations. Our simulations confirm that the observed Antarctic CN10 and cloud condensation nuclei (CCN) seasonal variations are due to the formation of secondary particles during the austral summer. From the austral winter to summer, the zonally averaged CN10 and CCN in the lower troposphere over Antarctica increase by a factor of ~4–6 and ~2–4, respectively. This study appears to show that the H2SO4-H2O IMN mechanism is able to account for the new particle formation frequently observed in the Antarctica region during the austral summer.
Highlights
Aerosol precursor gases emitted from oceans have been well recognized to play an important role in the Earth’s radiation budget and climate feedback processes
The main objective of this study is to investigate the well-recognized seasonal variations of new particle formation around Antarctic coastal areas associated with dimethyl sulfide (DMS) emissions by using a recently developed global size-resolved aerosol model and an ion-mediated nucleation (IMN) mechanism
Our simulations indicate that enhanced DMS emission, photochemistry, and [H2SO4] during the austral summer season lead to significant new particle formation and much higher particle number concentrations
Summary
Aerosol precursor gases emitted from oceans have been well recognized to play an important role in the Earth’s radiation budget and climate feedback processes. Charlson et al [2] proposed a negative feedback mechanism on the Earth’s climate involving the oceanic DMS emission, sulfate aerosol production, and cloud properties According to this hypothesis, a warmer climate would increase DMS emission and atmospheric DMS concentrations which in turn would lead to higher formation rates of sulfate aerosols and cloud condensation nuclei (CCN) abundance. Despite numerous studies undertaken since 1987 to verify the “CLAW” hypothesis and understand its relevance to today's climate issues, the magnitude and even the sign of the “CLAW” feedback mechanism remains unclear [3,4,5,6]. A lack of quantitative understanding of new particle formation processes is one of many significant gaps in the “CLAW”
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