Abstract
Abstract. Sub-micrometer particle size distributions measured during four summer cruises of the Swedish icebreaker Oden 1991, 1996, 2001, and 2008 were combined with dimethyl sulfide gas data, back trajectories, and daily maps of pack ice cover in order to investigate source areas and aerosol formation processes of the boundary layer aerosol in the central Arctic. With a clustering algorithm, potential aerosol source areas were explored. Clustering of particle size distributions together with back trajectories delineated five potential source regions and three different aerosol types that covered most of the Arctic Basin: marine, newly formed and aged particles over the pack ice. Most of the pack ice area with < 15% of open water under the trajectories exhibited the aged aerosol type with only one major mode around 40 nm. For newly formed particles to occur, two conditions had to be fulfilled over the pack ice: the air had spent 10 days while traveling over ever more contiguous ice and had traveled over less than 30% open water during the last 5 days. Additionally, the air had experienced more open water (at least twice as much as in the cases of aged aerosol) during the last 4 days before arrival in heavy ice conditions at Oden. Thus we hypothesize that these two conditions were essential factors for the formation of ultrafine particles over the central Arctic pack ice. In a comparison the Oden data with summer size distribution data from Alert, Nunavut, and Mt. Zeppelin, Spitsbergen, we confirmed the Oden findings with respect to particle sources over the central Arctic. Future more frequent broken-ice or open water patches in summer will spur biological activity in surface water promoting the formation of biological particles. Thereby low clouds and fogs and subsequently the surface energy balance and ice melt may be affected.
Highlights
The investigation of the summer aerosol over the central Arctic Ocean began with the first Swedish Arctic icebreaker expedition (Ymer-80) in 1980 (Lannefors et al, 1983) followed up later by a series of four international icebreaker expeditions to the summer central Arctic Ocean on the Swedish icebreaker Oden in the years 1991 (Leck et al, 1996), 1996 (Leck et al, 2001), 2001 (Leck et al, 2004), and 2008 (Tjernström et al, 2014).As illustrated in Fig. 1, several hypothesized sources may contribute to the aerosol over the central Arctic Ocean, and to the formation of low-level stratiform clouds and their effects on the surface energy balance
Sub-micrometer particle size distributions measured during four summer cruises of the Swedish icebreaker Oden 1991, 1996, 2001, and 2008 were combined with dimethyl sulfide gas data, back trajectories, and daily maps of pack ice cover in order to investigate source areas and aerosol formation processes of the boundary layer aerosol in the central Arctic
During the expedition in 1991, integrated samples of dimethyl sulfide (DMS) were analyzed by a gas chromatograph flame photometric detection (GC-FPD) system where a glass–fiber–wool coldtrap was used in the pre-concentration step
Summary
The investigation of the summer aerosol over the central Arctic Ocean began with the first Swedish Arctic icebreaker expedition (Ymer-80) in 1980 (Lannefors et al, 1983) followed up later by a series of four international icebreaker expeditions to the summer central Arctic Ocean on the Swedish icebreaker Oden in the years 1991 (Leck et al, 1996), 1996 (Leck et al, 2001), 2001 (Leck et al, 2004), and 2008 (Tjernström et al, 2014). Zone (MIZ) or locally from open leads over the pack ice has been found to result in raised concentrations of accumulation-mode particles within the high Arctic boundary layer (Heintzenberg et al, 2006; Chang et al, 2011; Heintzenberg and Leck, 2012; Kupiszewski et al, 2013; Hellén et al, 2012; Nilsson and Leck, 2002; Leck et al, 2013). While the four expeditions provided a wealth of new observations and understanding of the system of low-level clouds, their formation, and their effects on the boundarylayer and surface energy balance over the Arctic pack ice area, the ultimate partitioning of aerosol particles among potential source regions and processes remains elusive. With the combined data set and the clustering algorithm the main goal of the present study is to identify potential source regions of aerosol particles observed over the central summer Arctic. Gions, we aim at identifying factors controlling the aerosol life cycle over the inner Arctic
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