Abstract. Aerosols are an integral part of the Arctic climate system due to their
direct interaction with radiation and indirect interaction through cloud formation.
Understanding aerosol size distributions and their dynamics is crucial for
the ability to predict these climate relevant effects. When of favourable
size and composition, both long-range-transported – and locally
formed particles – may serve as cloud condensation nuclei (CCN). Small
changes of composition or size may have a large impact on the low CCN
concentrations currently characteristic of the Arctic environment. We
present a cluster analysis of particle size distributions (PSDs; size range
8–500 nm) simultaneously collected from three high Arctic sites during a
3-year period (2013–2015). Two sites are located in the Svalbard
archipelago: Zeppelin research station (ZEP; 474 m above ground) and the
nearby Gruvebadet Observatory (GRU; about 2 km distance from Zeppelin, 67 m above ground). The third site (Villum Research Station at Station Nord, VRS;
30 m above ground) is 600 km west-northwest of Zeppelin, at the tip of
north-eastern Greenland. The GRU site is included in an inter-site
comparison for the first time. K-means cluster analysis provided eight
specific aerosol categories, further combined into broad PSD classes with
similar characteristics, namely pristine low concentrations (12 %–14 %
occurrence), new particle formation (16 %–32 %), Aitken (21 %–35 %) and
accumulation (20 %–50 %). Confined for longer time periods by consolidated
pack sea ice regions, the Greenland site GRU shows PSDs with lower ultrafine-mode aerosol concentrations during summer but higher accumulation-mode aerosol concentrations during winter, relative to the Svalbard sites. By
association with chemical composition and cloud condensation nuclei
properties, further conclusions can be derived. Three distinct types of
accumulation-mode aerosol are observed during winter months. These are
associated with sea spray (largest detectable sizes, >400 nm),
Arctic haze (main mode at 150 nm) and aged accumulation-mode (main mode at
220 nm) aerosols. In contrast, locally produced particles, most likely of
marine biogenic origin, exhibit size distributions dominated by the
nucleation and Aitken mode during summer months. The obtained data and
analysis point towards future studies, including apportioning the relative
contribution of primary and secondary aerosol formation processes and
elucidating anthropogenic aerosol dynamics and transport and removal
processes across the Greenland Sea. In order to address important research
questions in the Arctic on scales beyond a singular station or measurement
events, it is imperative to continue strengthening international scientific
cooperation.