| 1. |
- Boy, M., et al.
(författare)
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Interactions between the atmosphere, cryosphere, and ecosystems at northern high latitudes
- 2019
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 19:3, s. 2015-2061
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Tidskriftsartikel (refereegranskat)abstract
- The Nordic Centre of Excellence CRAICC (Cryosphere-Atmosphere Interactions in a Changing Arctic Climate), funded by NordForsk in the years 2011-2016, is the largest joint Nordic research and innovation initiative to date, aiming to strengthen research and innovation regarding climate change issues in the Nordic region. CRAICC gathered more than 100 scientists from all Nordic countries in a virtual centre with the objectives of identifying and quantifying the major processes controlling Arctic warming and related feedback mechanisms, outlining strategies to mitigate Arctic warming, and developing Nordic Earth system modelling with a focus on short-lived climate forcers (SLCFs), including natural and anthropogenic aerosols. The outcome of CRAICC is reflected in more than 150 peer-reviewed scientific publications, most of which are in the CRAICC special issue of the journal Atmospheric Chemistry and Physics. This paper presents an overview of the main scientific topics investigated in the centre and provides the reader with a state-of-the-art comprehensive summary of what has been achieved in CRAICC with links to the particular publications for further detail. Faced with a vast amount of scientific discovery, we do not claim to completely summarize the results from CRAICC within this paper, but rather concentrate here on the main results which are related to feedback loops in climate change-cryosphere interactions that affect Arctic amplification.
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| 2. |
- Ickes, Luisa, 1986, et al.
(författare)
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The ice-nucleating activity of Arctic sea surface microlayer samples and marine algal cultures
- 2020
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 20:18, s. 11089-11117
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, sea spray as well as the biological material it contains has received increased attention as a source of ice-nucleating particles (INPs). Such INPs may play a role in remote marine regions, where other sources of INPs are scarce or absent. In the Arctic, these INPs can influence water-ice partitioning in low-level clouds and thereby the cloud lifetime, with consequences for the surface energy budget, sea ice formation and melt, and climate. Marine aerosol is of a diverse nature, so identifying sources of INPs is challenging. One fraction of marine bioaerosol (phytoplankton and their exudates) has been a particular focus of marine INP research. In our study we attempt to address three main questions. Firstly, we compare the ice-nucleating ability of two common phytoplankton species with Arctic seawater microlayer samples using the same instrumentation to see if these phytoplankton species produce ice-nucleating material with sufficient activity to account for the ice nucleation observed in Arctic microlayer samples. We present the first measurements of the ice-nucleating ability of two predominant phytoplankton species: Melosira arctica, a common Arctic diatom species, and Skeletonema marinoi, a ubiquitous diatom species across oceans worldwide. To determine the potential effect of nutrient conditions and characteristics of the algal culture, such as the amount of organic carbon associated with algal cells, on the ice nucleation activity, Skeletonema marinoi was grown under different nutrient regimes. From comparison of the ice nucleation data of the algal cultures to those obtained from a range of sea surface microlayer (SML) samples obtained during three different field expeditions to the Arctic (ACCACIA, NETCARE, and ASCOS), we found that they were not as ice active as the investigated microlayer samples, although these diatoms do produce ice-nucleating material. Secondly, to improve our understanding of local Arctic marine sources as atmospheric INPs we applied two aerosolization techniques to analyse the ice-nucleating ability of aerosolized microlayer and algal samples. The aerosols were generated either by direct nebulization of the undiluted bulk solutions or by the addition of the samples to a sea spray simulation chamber filled with artificial seawater. The latter method generates aerosol particles using a plunging jet to mimic the process of oceanic wave breaking. We observed that the aerosols produced using this approach can be ice active, indicating that the ice-nucleating material in seawater can indeed transfer to the aerosol phase. Thirdly, we attempted to measure ice nucleation activity across the entire temperature range relevant for mixed-phase clouds using a suite of ice nucleation measurement techniques - an expansion cloud chamber, a continuous-flow diffusion chamber, and a cold stage. In order to compare the measurements made using the different instruments, we have normalized the data in relation to the mass of salt present in the nascent sea spray aerosol. At temperatures above 248K some of the SML samples were very effective at nucleating ice, but there was substantial variability between the different samples. In contrast, there was much less variability between samples below 248 K. We discuss our results in the context of aerosol-cloud interactions in the Arctic with a focus on furthering our understanding of which INP types may be important in the Arctic atmosphere.
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| 3. |
- Johansson, Jana H., et al.
(författare)
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Global transport of perfluoroalkyl acids via sea spray aerosol
- 2019
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Ingår i: Environmental Science. - : Royal Society of Chemistry (RSC). - 2050-7887 .- 2050-7895. ; 21:4, s. 635-649
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Tidskriftsartikel (refereegranskat)abstract
- Perfluoroalkyl acids (PFAAs) are persistent organic pollutants found throughout the world's oceans. Previous research suggests that long-range atmospheric transport of these substances may be substantial. However, it remains unclear what the main sources of PFAAs to the atmosphere are. We have used a laboratory sea spray chamber to study water-to-air transfer of 11 PFAAs via sea spray aerosol (SSA). We observed significant enrichment of all PFAAs relative to sodium in the SSA generated. The highest enrichment was observed in aerosols with aerodynamic diameter < 1.6 mm, which had aerosol PFAA concentrations up to similar to 62 000 times higher than the PFAA water concentrations in the chamber. In surface microlayer samples collected from the sea spray chamber, the enrichment of the substances investigated was orders of magnitude smaller than the enrichment observed in the aerosols. In experiments with mixtures of structural isomers, a lower contribution of branched PFAA isomers was observed in the surface microlayer compared to the bulk water. However, no clear trend was observed in the comparison of structural isomers in SSA and bulk water. Using the measured enrichment factors of perfluorooctanoic acid and perfluorooctane sulfonic acid versus sodium we have estimated global annual emissions of these substances to the atmosphere via SSA as well as their global annual deposition to land areas. Our experiments suggest that SSA may currently be an important source of these substances to the atmosphere and, over certain areas, to terrestrial environments.
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| 4. |
- Lawler, M. J., et al.
(författare)
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New Insights Into the Composition and Origins of Ultrafine Aerosol in the Summertime High Arctic
- 2021
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 48:21
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Tidskriftsartikel (refereegranskat)abstract
- The summertime high Arctic atmosphere is characterized by extremely low aerosol abundance, such that small natural aerosol inputs have a strong influence on cloud formation and surface temperature. The physical sources and the mechanisms responsible for aerosol formation and development in this climate-critical and changing region are still uncertain. We report time-resolved measurements of high Arctic Aitken mode (∼20–60 nm diameter) aerosol composition during August–September 2018. During a significant Aitken mode formation event, the particles were composed of a combination of primary and secondary materials. These results highlight the importance of primary aerosol sources for high Arctic cloud formation, and they imply the action of a poorly understood atmospheric mechanism separating larger particles into multiple sub-particles.
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| 5. |
- Porter, Grace C.E., et al.
(författare)
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Highly Active Ice-Nucleating Particles at the Summer North Pole
- 2022
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Ingår i: Journal of Geophysical Research: Atmospheres. - 2169-8996 .- 2169-897X. ; 127:6
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Tidskriftsartikel (refereegranskat)abstract
- The amount of ice versus supercooled water in clouds is important for their radiative properties and role in climate feedbacks. Hence, knowledge of the concentration of ice-nucleating particles (INPs) is needed. Generally, the concentrations of INPs are found to be very low in remote marine locations allowing cloud water to persist in a supercooled state. We had expected the concentrations of INPs at the North Pole to be very low given the distance from open ocean and terrestrial sources coupled with effective wet scavenging processes. Here we show that during summer 2018 (August and September) high concentrations of biological INPs (active at >−20°C) were sporadically present at the North Pole. In fact, INP concentrations were sometimes as high as those recorded at mid-latitude locations strongly impacted by highly active biological INPs, in strong contrast to the Southern Ocean. Furthermore, using a balloon borne sampler we demonstrated that INP concentrations were often different at the surface versus higher in the boundary layer where clouds form. Back trajectory analysis suggests strong sources of INPs near the Russian coast, possibly associated with wind-driven sea spray production, whereas the pack ice, open leads, and the marginal ice zone were not sources of highly active INPs. These findings suggest that primary ice production, and therefore Arctic climate, is sensitive to transport from locations such as the Russian coast that are already experiencing marked climate change.
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| 6. |
- Salter, Matthew E., et al.
(författare)
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An empirically derived inorganic sea spray source function incorporating sea surface temperature
- 2015
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 15:19, s. 11047-11066
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Tidskriftsartikel (refereegranskat)abstract
- We have developed an inorganic sea spray source function that is based upon state-of-the-art measurements of sea spray aerosol production using a temperature-controlled plunging jet sea spray aerosol chamber. The size-resolved particle production was measured between 0.01 and 10 mu m dry diameter. Particle production decreased non-linearly with increasing seawater temperature (between -1 and 30 degrees C) similar to previous findings. In addition, we observed that the particle effective radius, as well as the particle surface, particle volume and particle mass, increased with increasing seawater temperature due to increased production of particles with dry diameters greater than 1 mu m. By combining these measurements with the volume of air entrained by the plunging jet we have determined the size-resolved particle flux as a function of air entrainment. Through the use of existing parameterisations of air entrainment as a function of wind speed, we were subsequently able to scale our laboratory measurements of particle production to wind speed. By scaling in this way we avoid some of the difficulties associated with defining the white area of the laboratory whitecap - a contentious issue when relating laboratory measurements of particle production to oceanic whitecaps using the more frequently applied whitecap method. The here-derived inorganic sea spray source function was implemented in a Lagrangian particle dispersion model (FLEXPART - FLEXible PARTicle dispersion model). An estimated annual global flux of inorganic sea spray aerosol of 5.9 +/- 0.2 Pg yr(-1) was derived that is close to the median of estimates from the same model using a wide range of existing sea spray source functions. When using the source function derived here, the model also showed good skill in predicting measurements of Na+ concentration at a number of field sites further underlining the validity of our source function. In a final step, the sensitivity of a large-scale model (NorESM - the Norwegian Earth System Model) to our new source function was tested. Compared to the previously implemented parameterisation, a clear decrease of sea spray aerosol number flux and increase in aerosol residence time was observed, especially over the Southern Ocean. At the same time an increase in aerosol optical depth due to an increase in the number of particles with optically relevant sizes was found. That there were noticeable regional differences may have important implications for aerosol optical properties and number concentrations, subsequently also affecting the indirect radiative forcing by non-sea spray anthropogenic aerosols.
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| 7. |
- Salter, Matthew E., et al.
(författare)
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Calcium enrichment in sea spray aerosol particles
- 2016
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Ingår i: Geophysical Research Letters. - : Blackwell Publishing. - 0094-8276 .- 1944-8007. ; 43:15, s. 8277-8285
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Tidskriftsartikel (refereegranskat)abstract
- Sea spray aerosol particles are an integral part of the Earth's radiation budget. To date, the inorganic composition of nascent sea spray aerosol particles has widely been assumed to be equivalent to the inorganic composition of seawater. Here we challenge this assumption using a laboratory sea spray chamber containing both natural and artificial seawater, as well as with ambient aerosol samples collected over the central Arctic Ocean during summer. We observe significant enrichment of calcium in submicrometer (<1 μm in diameter) sea spray aerosol particles when particles are generated from both seawater sources in the laboratory as well as in the ambient aerosols samples. We also observe a tendency for increasing calcium enrichment with decreasing particle size. Our results suggest that calcium enrichment in sea spray aerosol particles may be environmentally significant with implications for our understanding of sea spray aerosol, its impact on Earth's climate, as well as the chemistry of the marine atmosphere.
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| 8. |
- Salter, Matthew E., et al.
(författare)
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On the seawater temperature dependence of the sea spray aerosol generated by a continuous plunging jet
- 2014
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Ingår i: Journal of Geophysical Research - Atmospheres. - 2169-897X .- 2169-8996. ; 119:14, s. 9052-9072
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Tidskriftsartikel (refereegranskat)abstract
- Breaking waves on the ocean surface produce bubbles which, upon bursting, deliver seawater constituents into the atmosphere as sea spray aerosol particles. One way of investigating this process in the laboratory is to generate a bubble plume by a continuous plunging jet. We performed a series of laboratory experiments to elucidate the role of seawater temperature on aerosol production from artificial seawater free from organic contamination using a plunging jet. The seawater temperature was varied from -1.3 degrees C to 30.1 degrees C, while the volume of air entrained by the jet, surface bubble size distributions, and size distribution of the aerosol particles produced was monitored. We observed that the volume of air entrained decreased as the seawater temperature was increased. The number of surface bubbles with film radius smaller than 2 mm decreased nonlinearly with seawater temperature. This decrease was coincident with a substantial reduction in particle production. The number concentrations of particles with dry diameter less than similar to 1 mu m decreased substantially as the seawater temperature was increased from -1.3 degrees C to similar to 9 degrees C. With further increase in seawater temperature (up to 30 degrees C), a small increase in the number concentration of larger particles (dry diameter >similar to 0.3 mu m) was observed. Based on these observations, we infer that as seawater temperature increases, the process of bubble fragmentation changes, resulting in decreased air entrainment by the plunging jet, as well as the number of bubbles with film radius smaller than 2 mm. This again results in decreased particle production with increasing seawater temperature.
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| 9. |
- Zinke, Julika, 1995-
(författare)
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Factors influencing emission fluxes and bacterial enrichment in sea spray aerosols : Insights from laboratory and field studies
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sea spray aerosol (SSA) is one of the major natural aerosol sources and is produced when wave breaking entrains air into ocean surface water, which subsequently breaks up into bubbles. These bubbles rise to the surface and can scavenge biogenic material. Once they reach the surface, they burst and produce both a large number of relatively small film drops that result from the disintegration of the bubble film cap and a smaller number of jet drops that result from the collapse of the bubble cavity and are typically larger in size than the film drops. The production of SSA is influenced by several factors, including wind speed, sea state, seawater temperature, salinity, and the physicochemical and biological condition of the ocean. SSA can significantly impact Earth's radiation budget by scattering incoming solar radiation directly and by acting as cloud condensation nuclei. To improve our understanding of the impact of sea spray aerosols on the Earth’s climate, it is critical to understand the physical mechanisms which determine the size-resolved SSA production flux. Furthermore, SSA can be a vector for the emission of primary biological airborne particles (PBAP) from the oceans to the atmosphere. PBAP encompass bacteria, viruses, pollen and spores and can be present in the atmosphere in form of agglomerates, single particles or cell fractions. Although, the abundance of PBAP typically only make up < 0.1% of the number of aerosols, this does not imply their insignificance. On the contrary, PBAP are known to be very efficient cloud- and ice condensation nuclei and thus can influence cloud properties such as cloud phase, albedo and lifetime, thereby affecting the Earth’s climate as well as biogeochemical cycles. As the Earth is 70% covered by oceans, of which most could be characterized as remote, quantifying the PBAP emissions over these waters are important for the enhancement of climate models.The goal of this thesis was to study the factors impacting SSA emissions and the emission of primary biological particles with SSA with particular focus on bacteria emissions. This was done both through laboratory and field experiments in the Baltic Sea and in the Azores archipelago using a plunging jet sea spray simulation chamber and various techniques to characterize aerosol emissions. More specifically, a parameterization for the SSA production flux as a function of salinity and temperature was derived from laboratory experiments and a wind speed and sea state dependent parameterization were derived from ambient eddy covariance (EC) flux measurements in the Baltic Sea. The combination of EC flux measurements and laboratory generated SSA allowed to derive a chamber specific scaling factor that could be applied to derive bacteria emission fluxes ranging between 16-63 cells m−2 s−1 from the Baltic Sea. Bacteria were found to be 13-488 and 9-148 times enriched in SSA compared to the underlying seawater from mesocosm experiments in the Baltic Sea and Azores, respectively. A comparison of single cell abundance estimates from fluorescence microscopy and real-time measurements of PBAP with diameters > 0.8 µm using a bioaerosol sensor revealed that the latter yielded consistently lower concentrations. The discrepancy was explained by differences in the sampling approach and size cut-offs (i.e. single cells versus agglomerates or particle-attached cells). As such, both methods are applicable to different research questions and should be considered complementary.An analysis of the microbial community composition in the aerosols and underlying seawater showed selective aerosolization of certain bacteria taxa. Furthermore, selective growth and a decrease in alpha diversity in the seawater was observed when the mesocosm experiments were operated in a closed mode (meaning that the seawater was not exchanged over the duration of each experiment), which can however be circumvented by continuously replacing the water in the mesocosm.Ambient measurements of PBAP revealed diurnal variations with a peak during the early morning hours that was correlated to changes wind speed, wave height, air temperature, relative humidity, latent and sensitive heat flux.
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| 10. |
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