Near-surface profiles of aerosol number concentration and temperature over the Arctic Ocean

Held, Andreas; Orsini, D.; Vaattovaara, P.; Tjernström, Michael; Leck, Caroline

doi:10.5194/amt-4-1603-2011

Cited by 18 publications

(12 citation statements)

References 46 publications

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“…The observed number size distribution for all HP (Fig. 5, lower panel) is in agreement with results from the high Arctic reported by Hillamo et al (2001), who observed the first maximum in sulfate-containing aerosol particles at diameters > 80 nm and in ammonium and MSA-containing particles at diameters > 100 nm.…”

Section: Halo Particlessupporting

confidence: 91%

Size-resolved morphological properties of the high Arctic summer aerosol during ASCOS-2008

2016

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Abstract. The representation of aerosol properties and processes in climate models is fraught with large uncertainties. Especially at high northern latitudes a strong underprediction of aerosol concentrations and nucleation events is observed and can only be constrained by in situ observations based on the analysis of individual aerosol particles. To further reduce the uncertainties surrounding aerosol properties and their potential role as cloud condensation nuclei this study provides observational data resolved over size on morphological and chemical properties of aerosol particles collected in the summer high Arctic, north of 80° N. Aerosol particles were imaged with scanning and transmission electron microscopy and further evaluated with digital image analysis. In total, 3909 aerosol particles were imaged and categorized according to morphological similarities into three gross morphological groups: single particles, gel particles, and halo particles. Single particles were observed between 15 and 800 nm in diameter and represent the dominating type of particles (82 %). The majority of particles appeared to be marine gels with a broad Aitken mode peaking at 70 nm and accompanied by a minor fraction of ammonium (bi)sulfate with a maximum at 170 nm in number concentration. Gel particles (11 % of all particles) were observed between 45 and 800 nm with a maximum at 154 nm in diameter. Imaging with transmission electron microscopy allowed further morphological discrimination of gel particles in "aggregate" particles, "aggregate with film" particles, and "mucus-like" particles. Halo particles were observed above 75 nm and appeared to be ammonium (bi)sulfate (59 % of halo particles), gel matter (19 %), or decomposed gel matter (22 %), which were internally mixed with sulfuric acid, methane sulfonic acid, or ammonium (bi)sulfate with a maximum at 161 nm in diameter. Elemental dispersive X-ray spectroscopy analysis of individual particles revealed a prevalence of the monovalent ions Na+/K+ for single particles and aggregate particles and of the divalent ions Ca2+/Mg2+ for aggregate with film particles and mucus-like particles. According to these results and other model studies, we propose a relationship between the availability of Na+/K+ and Ca2+/Mg2+ and the length of the biopolymer molecules participating in the formation of the three-dimensional gel networks.

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Section: Halo Particlessupporting

confidence: 91%

Size-resolved morphological properties of the high Arctic summer aerosol during ASCOS-2008

2016

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“…Simultaneous and independent gradient measurements of particle concentrations presented in Held et al (2011b) corroborate the finding that open leads can indeed act as particle sources in the Arctic Ocean. Overall, the direct contribution of the open lead particle emissions to the atmospheric aerosol number concentration could only explain a few percent of the observed total particle number variability measured onboard the ship.…”

Section: Aerosol Transport Over the Pack Icesupporting

confidence: 68%

The summer aerosol in the central Arctic 1991–2008: did it change or not?

Heintzenberg

Leck

2012

Atmos. Chem. Phys.

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Abstract. In the course of global warming dramatic changes are taking place in the Arctic and boreal environments. However, physical aerosol data in from the central summer Arctic taken over the course of 18 yr from 1991 to 2008 do not show systematic year-to-year changes, albeit substantial interannual variations. Besides the limited extent of the data several causes may be responsible for these findings. The processes controlling concentrations and particle size distribution of the aerosol over the central Arctic perennial pack ice area, north of 80 • , may not have changed substantially during this time. Environmental changes are still mainly effective in the marginal ice zone, the ice-free waters and continental rims and have not propagated significantly into the central Arctic yet where they could affect the local aerosol and its sources. The analysis of meteorological conditions of the four expedition summers reveal substantial variations which we see as main causes of the measured variations in aerosol parameters. With combined lognormal fits of the hourly number size distributions of the four expeditions representative mode parameters for the summer aerosol in the central Arctic have been calculated. The combined aerosol statistics discussed in the present paper provide comprehensive physical data on the summer aerosol in the central Arctic. These data are the only surface aerosol information from this region.

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“…With the suggestion from the previous expeditions that an unknown fraction of airborne and in-cloud aerosol were polymer gels originating either in local open water leads or from a distant source, such as the MIZ, an attempt was made to quantify the net contribution of the local lead aerosol flux to the observed aerosol concentrations. Direct eddy covariance observations of the net aerosol flux into the atmosphere were performed at the ice edge near the "Open Lead" site (Held et al, 2011a); the results compared well with independent estimates obtained from aerosol concentration gradients very close to the water surface (Held et al, 2011b).…”

Section: Aerosols In Air and In Cloud Dropletsmentioning

confidence: 70%

“…The response time of the particle counter, including the sampling line, was approximately 1.4 s. Near-surface profiles of aerosol number concentration and temperature were also measured using a gradient-pole technique, where the pole was positioned on a tripod so that its inlet could be lifted to different heights. The inlet was positioned manually with a repeatable accuracy of ± 1 cm between the surface and a maximum height of 1.6 m; see Held et al (2011b) for a detailed description.…”

Section: Sub-micrometer Aerosol Non-refractory Chemical Composition (mentioning

confidence: 99%

The Arctic Summer Cloud Ocean Study (ASCOS): overview and experimental design

et al. 2014

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Abstract. The climate in the Arctic is changing faster than anywhere else on earth. Poorly understood feedback processes relating to Arctic clouds and aerosol-cloud interactions contribute to a poor understanding of the present changes in the Arctic climate system, and also to a large spread in projections of future climate in the Arctic. The problem is exacerbated by the paucity of research-quality observations in the central Arctic. Improved formulations in climate models require such observations, which can only come from measurements in situ in this difficult-to-reach region with logistically demanding environmental conditions.The Arctic Summer Cloud Ocean Study (ASCOS) was the most extensive central Arctic Ocean expedition with an atmospheric focus during the International Polar Year (IPY) [2007][2008]. ASCOS focused on the study of the formation and life cycle of low-level Arctic clouds. ASCOS departed from Longyearbyen on Svalbard on 2 August and returned on 9 September 2008. In transit into and out of the pack ice, four short research stations were undertaken in the Fram Strait: two in open water and two in the marginal ice zone. After traversing the pack ice northward, an ice camp was set up on 12 August at 87 • 21 N, 01 • 29 W and remained in operation through 1 September, drifting with the ice. During this time, extensive measurements were taken of atmospheric gas and particle chemistry and physics, mesoscale and boundarylayer meteorology, marine biology and chemistry, and upper ocean physics.ASCOS provides a unique interdisciplinary data set for development and testing of new hypotheses on cloud processes, their interactions with the sea ice and ocean and associated physical, chemical, and biological processes and interactions. For example, the first-ever quantitative observation of bubbles in Arctic leads, combined with the unique discovery of marine organic material, polymer gels with an origin in the ocean, inside cloud droplets suggests the possibility of primary marine organically derived cloud condensation nuclei in Arctic stratocumulus clouds. Direct observations of surface fluxes of aerosols could, however, not explain observed variability in aerosol concentrations, and the balance between local and remote aerosols sources remains open. Lack of cloud condensation nuclei (CCN) was at times a controlling factor in low-level cloud formation, and hence for the impact of clouds on the surface energy budget. AS-COS provided detailed measurements of the surface energy balance from late summer melt into the initial autumn freezeup, and documented the effects of clouds and storms on the surface energy balance during this transition. In addition to such process-level studies, the unique, independent ASCOS data set can and is being used for validation of satellite retrievals, operational models, and reanalysis data sets.

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Near-surface profiles of aerosol number concentration and temperature over the Arctic Ocean

Cited by 18 publications

References 46 publications

Size-resolved morphological properties of the high Arctic summer aerosol during ASCOS-2008

Size-resolved morphological properties of the high Arctic summer aerosol during ASCOS-2008

The summer aerosol in the central Arctic 1991–2008: did it change or not?

The Arctic Summer Cloud Ocean Study (ASCOS): overview and experimental design

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