Abstract
Abstract. Single-particle mass-spectrometric measurements were carried out in the high Arctic north of 80° during summer 2008. The campaign took place onboard the icebreaker Oden and was part of the Arctic Summer Cloud Ocean Study (ASCOS). The instrument deployed was an aerosol time-of-flight mass spectrometer (ATOFMS) that provides information on the chemical composition of individual particles and their mixing state in real time. Aerosols were sampled in the marine boundary layer at stations in the open ocean, in the marginal ice zone, and in the pack ice region. The largest fraction of particles detected for subsequent analysis in the size range of the ATOFMS between approximately 200 and 3000 nm in diameter showed mass-spectrometric patterns, indicating an internal mixing state and a biomass burning and/or biofuel source. The majority of these particles were connected to an air mass layer of elevated particle concentration mixed into the surface mixed layer from the upper part of the marine boundary layer. The second largest fraction was represented by sea salt particles. The chemical analysis of the over-ice sea salt aerosol revealed tracer compounds that reflect chemical aging of the particles during their long-range advection from the marginal ice zone, or open waters south thereof prior to detection at the ship. From our findings we conclude that long-range transport of particles is one source of aerosols in the high Arctic. To assess the importance of long-range particle sources for aerosol–cloud interactions over the inner Arctic in comparison to local and regional biogenic primary aerosol sources, the chemical composition of the detected particles was analyzed for indicators of marine biological origin. Only a minor fraction showed chemical signatures of potentially ocean-derived primary particles of that kind. However, a chemical bias in the ATOFMS's detection capabilities observed during ASCOS might suggest the presence of a particle type of unknown composition and source. In general, the study suffered from low counting statistics due to the overall small number of particles found in this pristine environment, the small sizes of the prevailing aerosol below the detection limit of the ATOFMS, and its low hit rate. To our knowledge, this study reports on the first in situ single-particle mass-spectrometric measurements in the marine boundary layer of the high-Arctic pack ice region.
Highlights
The Arctic pack ice region is undergoing dramatic changes due to global warming (e.g., IPCC, 2007; Jeffries and Richter-Menge, 2012)
Data collected during three sampling periods at different locations are presented: firstly, data from an open water station (OW) at 0:00 to 12:00 UTC on 3 August 2008 (78.2◦ N, 7.5◦ E); secondly, from a marginal ice zone station (MIZ) on 4 August 2008 12:00 to 5 August 12:00 UTC (79.9◦ N, 6.1◦ E); and thirdly, measurements taken at an ice floe station (IF) in the pack ice (> 87◦ N) when the icebreaker was moored to an ice floe and drifted passively
The chemical composition of individual aerosol particles in the size range between approximately 200 nm and 3 μm in diameter was measured in the marine boundary layer with a single-particle mass spectrometer at three different stations: at an open water station, at a marginal ice station, and at an ice floe station in the pack ice region
Summary
The Arctic pack ice region is undergoing dramatic changes due to global warming (e.g., IPCC, 2007; Jeffries and Richter-Menge, 2012). B. Sierau et al.: Single-particle characterization of high-Arctic aerosol the microphysical structure and lifetime of clouds with possible consequences for the planetary albedo and the surface energy budget and for the melting and freezing of the perennial sea ice (Intrieri et al, 2002; Sedlar et al, 2011; Tjernström et al, 2005). Sierau et al.: Single-particle characterization of high-Arctic aerosol the microphysical structure and lifetime of clouds with possible consequences for the planetary albedo and the surface energy budget and for the melting and freezing of the perennial sea ice (Intrieri et al, 2002; Sedlar et al, 2011; Tjernström et al, 2005) Both the radiative effects of aerosols and their role in cloud forming processes depend on the number, size, chemical properties, and mixing state of the particles. This includes measuring the particles’ physicochemical properties in situ and elucidating their atmospheric history, i.e., assigning particle sources and understanding the processes shaping the aerosols during their residence time in the atmosphere
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