Potential source regions and processes of aerosol in the summer Arctic

Abstract

Abstract. Sub-micrometer particle size distributions measured during four summer cruises of the Swedish icebreaker Oden 1991Oden , 1996Oden , 2001Oden , 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.

The free troposphere as a potential source of arctic boundary layer aerosol particles

“…Much attention has been given to this problem, yet the modeling of clouds in regional and general circulation models remains a challenge. Mauritsen et al [2011], Heintzenberg et al [2015], and Leck and Svensson [2015] report surface concentrations that are generally below 100 cm À3 and occasionally below 1 cm À3 , both in the marginal ice zone and over the pack ice. Sufficiently low CCN concentrations in the Arctic may even prevent the formation of clouds [Mauritsen et al, 2011].…”

“…The representation of mixed-phase Arctic clouds, and its links to cloud condensation nucleus (CCN) concentrations, is particularly challenging [Wyser et al, 2007;Sotiropoulou et al, 2016]. The low concentrations are attributed to inefficient long-range transport [Klonecki et al, 2003;Stohl, 2006;Heintzenberg et al, 2015] and removal by precipitation [Bigg et al, 1996;Bigg and Leck, 2001;Nilsson and Leck, 2002;Heintzenberg et al, 2006;Garrett et al, 2010]. Improvements in cloud representation in models require a better understanding of the sources and sinks of CCN in the Arctic.…”

Contributions of transported Prudhoe Bay oil field emissions to the aerosol population in Utqiaġvik, Alaska

“…Prudhoe Bay air masses had a significantly (95 % confidence interval) higher median concentration (407 particles cm −3 ) compared to Arctic Ocean air masses (294 particles cm −3 ), similar to the trends observed during the 2015 study. The median particle concentration within Arctic Ocean air masses is similar to the median particle number concentrations during August at Station Nord, Greenland (227 particles cm −3 ; Nguyen et al, 2016), and Alert, Canada (∼ 160 particles cm −3 ; Croft et al, 2016), during September at Tiksi, Russia (222 particles cm −3 ; Asmi et al, 2016), and within the range of observations onboard the Swedish icebreaker Oden from July to September during multiple central Arctic Ocean studies when the air masses were exposed to the open ocean (90-210 particles cm −3 ; Heintzenberg et al, 2015). However, the median particle number concentration during August in Tiksi, Russia (383 particles cm −3 ), is similar to the median concentration of air masses influenced by Prudhoe Bay (407 particles cm −3 ) even though the elevated number concentrations in Tiksi are due to biogenic influence, leading to new particle formation and growth (Asmi et al, 2016).…”

The influence of local oil exploration and regional wildfires on summer 2015 aerosol over the North Slope of Alaska

“…Regardless of their episodic behavior, summertime sub-Arctic boreal fires can produce substantial quantities of aerosol that can reside in the troposphere for 1-2 weeks (Stohl et al, 2013). The Arctic summertime atmosphere is historically less polluted as compared to the rest of the year (Quinn et al, 2002;Leaitch et al, 2013;Heintzenberg et al, 2015); thus it is critical to assess the impacts of potentially important local sources of summertime aerosol on Arctic radiation and cloud microphysical processes. Here, we present aerosol and trace gas observations from ARM's Fifth Airborne Carbon Measurements (ACME-V) field campaign to evaluate local sources during the summer of 2015 in the Alaskan Arctic.…”