Ice-nucleating particle concentration measurements from Ny-Ålesund during the Arctic spring–summer in 2018
Authors: Rinaldi Matteo , Hiranuma Naruki , Santachiara Gianni , Mazzola Mauro , Mansour Karam , Paglione Marco , Rodriguez Cheyanne A. , Traversi Rita , Becagli Silvia , Cappelletti David , Belosi Franco 
Published: October 2021

Abstract. In this study, we present atmospheric ice-nucleating particle (INP)
concentrations from the Gruvebadet (GVB) observatory in Ny-Ålesund
(Svalbard). All aerosol particle sampling activities were conducted in April–August 2018. Ambient INP concentrations (nINP) were measured for aerosol
particles collected on filter samples by means of two offline instruments:
the Dynamic Filter Processing Chamber (DFPC) and the West Texas Cryogenic
Refrigerator Applied to Freezing Test system (WT-CRAFT) to assess
condensation and immersion freezing, respectively. DFPC measured nINPs for a
set of filters collected through two size-segregated inlets: one for
transmitting particulate matter of less than 1 µm (PM1), the
other for particles with an aerodynamic diameter of less than 10 µm
aerodynamic diameter (PM10). Overall, nINPPM10 measured by DFPC at
a water saturation ratio of 1.02 ranged from 3 to 185 m−3 at
temperatures (Ts) of −15 to −22 ∘C. On average, the super-micrometer INP (nINPPM10-nINPPM1) accounted for
approximately 20 %–30 % of nINPPM10 in spring, increasing in summer to
45 % at −22 ∘C and 65 % at −15 ∘C. This increase in super-micrometer INP fraction towards summer suggests that super-micrometer
aerosol particles play an important role as the source of INPs in the
Arctic. For the same T range, WT-CRAFT measured 1 to 199 m−3. Although
the two nINP datasets were in general agreement, a notable nINP offset was
observed, particularly at −15 ∘C. Interestingly, the results of
both DFPC and WT-CRAFT measurements did not show a sharp increase in nINP
from spring to summer. While an increase was observed in a subset of our
data (WT-CRAFT, between −18 and −21 ∘C), the spring-to-summer
nINP enhancement ratios never exceeded a factor of 3. More evident seasonal variability was found, however, in our activated fraction (AF) data, calculated by scaling the measured nINP to the total aerosol particle
concentration. In 2018, AF increased from spring to summer. This seasonal AF
trend corresponds to the overall decrease in aerosol concentration towards
summer and a concomitant increase in the contribution of super-micrometer particles. Indeed, the AF of coarse particles resulted markedly higher than
that of sub-micrometer ones (2 orders of magnitude). Analysis of low-traveling back-trajectories and meteorological conditions at GVB matched to our INP data suggests that the summertime INP population is
influenced by both terrestrial (snow-free land) and marine sources. Our
spatiotemporal analyses of satellite-retrieved chlorophyll a, as well as spatial source attribution, indicate that the maritime INPs at GVB may come
from the seawaters surrounding the Svalbard archipelago and/or in proximity
to Greenland and Iceland during the observation period. Nevertheless,
further analyses, performed on larger datasets, would be necessary to reach
firmer and more general conclusions.