Abstract. Few measurements of aerosol chemical composition have been made during the
winter–spring transition (following polar sunrise) to constrain Arctic
aerosol–cloud–climate feedbacks. Herein, we report the first measurements
of individual particle chemical composition near Utqiaġvik (Barrow),
Alaska, in winter (seven sample days in January and February 2014).
Individual particles were analyzed by computer-controlled scanning electron
microscopy with energy dispersive X-ray spectroscopy (CCSEM-EDX, 24 847
particles), Raman microspectroscopy (300 particles), and scanning
transmission X-ray microscopy with near-edge X-ray absorption fine structure
spectroscopy (STXM-NEXAFS, 290 particles). Sea spray aerosol (SSA) was
observed in all samples, with fresh and aged SSA comprising 99 %, by
number, of 2.5–7.5 µm
diameter particles, 65–95 % from 0.5–2.5 µm, and
50–60 % from 0.1–0.5 µm, indicating SSA is the dominant
contributor to accumulation and coarse-mode aerosol during the winter. The
aged SSA particles were characterized by reduced chlorine content with
94 %, by number, internally mixed with secondary sulfate (39 %, by
number, internally mixed with both nitrate and sulfate), indicative of
multiphase aging reactions during transport. There was a large number
fraction (40 % of 1.0–4.0 µm diameter particles) of aged SSA
during periods when particles were transported from near Prudhoe Bay,
consistent with pollutant emissions from the oil fields participating in
atmospheric processing of aerosol particles. Organic carbon and sulfate
particles were observed in all samples and comprised 40–50 %, by number,
of 0.1–0.4 µm diameter particles, indicative of Arctic haze
influence. Soot was internally mixed with organic and sulfate components. All
sulfate was mixed with organic carbon or SSA particles. Therefore, aerosol
sources in the Alaskan Arctic and resulting aerosol chemical mixing states
need to be considered when predicting aerosol climate effects, particularly
cloud formation, in the winter Arctic.
Review of “Linking variations in sea spray aerosol particle hygroscopicity to composition during two microcosm experiments”, by S.D. Forestieri et al