Abstract

Abstract. Measurements of submicron aerosol chemical composition were made over the central Arctic Ocean from 5 August to 8 September 2008 as a part of the Arctic Summer Cloud Ocean Study (ASCOS) using an aerosol mass spectrometer (AMS). The median levels of sulphate and organics for the entire study were 0.051 and 0.055 μ g m−3, respectively. Positive matrix factorisation was performed on the entire mass spectral time series and this enabled marine biogenic and continental sources of particles to be separated. These factors accounted for 33% and 36% of the sampled ambient aerosol mass, respectively, and they were both predominantly composed of sulphate, with 47% of the sulphate apportioned to marine biogenic sources and 48% to continental sources, by mass. Within the marine biogenic factor, the ratio of methane sulphonate to sulphate was 0.25 ± 0.02, consistent with values reported in the literature. The organic component of the continental factor was more oxidised than that of the marine biogenic factor, suggesting that it had a longer photochemical lifetime than the organics in the marine biogenic factor. The remaining ambient aerosol mass was apportioned to an organic-rich factor that could have arisen from a combination of marine and continental sources. In particular, given that the factor does not correlate with common tracers of continental influence, we cannot rule out that the organic factor arises from a primary marine source.

Highlights

  • The sources and chemical composition of Arctic aerosol are still poorly represented in models

  • Mass concentrations for the non-refractory components of aerosol measured by the aerosol mass spectrometer (AMS) are shown in Fig. 2, with the shaded areas showing the times of the stations

  • Ammonium is not included since it was below its detection limit of 0.04 μgm−3 86 % of the time, it was still included in the fragmentation table

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Summary

Introduction

The sources and chemical composition of Arctic aerosol are still poorly represented in models. A series of three previous international ice-breaker expeditions to the central Arctic Ocean (north of 85◦ N) during the summers of 1991 (IAOE-91) (Leck et al, 1996), 1996 (AOE-96) (Leck et al, 2001) and 2001 (AOE-2001) (Leck et al, 2004; Tjernstrom, 2005) has greatly contributed to our knowledge of aerosol sources and composition at these northern latitudes It was observed during IAOE-91 that submicron sulphur-containing particles over the Arctic pack ice are efficiently scavenged by fogs and low clouds and have average residence times of ≈20 h (Nilsson and Leck, 2002). These boundary layer data can be compared to free tropospheric measurements made during other International Polar Year campaigns where biomass burning was found to dominate the aerosol loading (Brock et al, 2011)

Arctic summer cloud ocean study
Aerosol mass spectrometer
Proton-transfer-reaction time-of-flight mass spectrometer
Radon 222
Lead 210
Positive matrix factorisation
Potential source contribution function
FLEXPART
Contamination from research activities
General AMS results
PMF results
F4: Ship Emission
Marine biogenic factor
F1: F2: F3: F4
Continental factor
F4: Ship Emissions
Organic factor
Ship emission factor
Conclusions
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