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  • Dragosics, Monika; Meinander, Outi; Jonsdottir, Tinna; Durig, Tobias; De Leeuw, Gerrit; Palsson, Finnur; Dagsson-Waldhauserova, Pavla; Thorsteinsson, Throstur (2016)
    In the Arctic region, Iceland is an important source of dust due to ash production from volcanic eruptions. In addition, dust is resuspended from the surface into the atmosphere as several dust storms occur each year. During volcanic eruptions and dust storms, material is deposited on the glaciers where it influences their energy balance. The effects of deposited volcanic ash on ice and snow melt were examined using laboratory and outdoor experiments. These experiments were made during the snow melt period using two different ash grain sizes (1 phi and 3.5 phi) from the Eyjafjallajokull 2010 eruption, collected on the glacier. Different amounts of ash were deposited on snow or ice, after which the snow properties and melt were measured. The results show that a thin ash layer increases the snow and ice melt but an ash layer exceeding a certain critical thickness caused insulation. Ash with 1 phi in grain size insulated the ice below at a thickness of 9-15 mm. For the 3.5 phi grain size, the insulation thickness is 13 mm. The maximum melt occurred at a thickness of 1 mm for the 1 phi and only 1-2 mm for 3.5 phi ash. A map of dust concentrations on Vatnajokull that represents the dust deposition during the summer of 2013 is presented with concentrations ranging from 0.2 up to 16.6 g m(-2).
  • Boy, Michael; Thomson, Eric S.; Acosta Navarro, Juan-C.; Arnalds, Olafur; Batchvarova, Ekaterina; Bäck, Jaan; Berninger, Frank; Bilde, Merete; Brasseur, Zoé; Dagsson-Waldhauserova, Pavla; Castarède, Dimitri; Dalirian, Maryam; de Leeuw, Gerrit; Dragosics, Monika; Duplissy, Ella-Maria; Duplissy, Jonathan; Ekman, Annica M. L.; Fang, Keyan; Gallet, Jean-Charles; Glasius, Marianne; Gryning, Sven-Erik; Grythe, Henrik; Hansson, Hans-Christen; Hansson, Margareta; Isaksson, Elisabeth; Iversen, Trond; Jonsdottir, Ingibjorg; Kasurinen, Ville; Kirkevåg, Alf; Korhola, Atte; Krejci, Radovan; Kristjansson, Jon Egill; Lappalainen, Hanna K.; Lauri, Antti; Leppäranta, Matti; Lihavainen, Heikki; Makkonen, Risto; Massling, Andreas; Meinander, Outi; Nilsson, E. Douglas; Olafsson, Haraldur; Pettersson, Jan B. C.; Prisle, Nønne L.; Riipinen, Ilona; Roldin, Pontus; Ruppel, Meri; Salter, Matthew; Sand, Maria; Seland, Øyvind; Seppä, Heikki; Skov, Henrik; Soares, Joana; Stohl, Andreas; Ström, Johan; Svensson, Jonas; Swietlicki, Erik; Tabakova, Ksenia; Thorsteinsson, Throstur; Virkkula, Aki; Weyhenmeyer, Gesa A.; Wu, Yusheng; Zieger, Paul; Kulmala, Markku (2019)
    The Nordic Centre of Excellence CRAICC (CRyosphere-Atmosphere Interactions in a Changing Arctic Climate), funded by NordForsk in the years 2011–2016, was 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 to identify and quantify the major processes controlling Arctic warming and related feedback mechanisms, to outline strategies to mitigate Arctic warming and to develop Nordic Earth System modelling with a focus on the short-lived climate forcers (SLCF), 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 manuscript presents an overview on the main scientific topics investigated in the Centre and provides the reader a state-of-the-art comprehensive summary of what has been achieved in CRAICC with links to the particular publications for further detail. Facing the vast amount of outcomes we are not claiming to cover all results from CRAICC in this manuscript but concentrate here on the main results which are related to the feedback loops in the climate change-cryosphere interaction scheme affecting the Arctic amplification.
  • Peltoniemi, J. I.; Gritsevich, M.; Hakala, T.; Dagsson-Waldhauserova, P.; Arnalds, O.; Anttila, K.; Hannula, H. -R.; Kivekas, N.; Lihavainen, H.; Meinander, O.; Svensson, J.; Virkkula, A.; de Leeuw, G. (2015)
    In order to quantify the effects of absorbing contaminants on snow, a series of spectral reflectance measurements were conducted. Chimney soot, volcanic sand, and glaciogenic silt were deposited on a natural snow surface in a controlled way as a part of the Soot on Snow (SoS) campaign. The bidirectional reflectance factors of these soiled surfaces and untouched snow were measured using the Finnish Geodetic Institute's Field Goniospectropolariradiometer, FIGIFIGO. A remarkable feature is the fact that the absorbing contaminants on snow enhanced the metamorphism of snow under strong sunlight in our experiments. Immediately after deposition, the contaminated snow surface appeared darker than the natural snow in all viewing directions, but the absorbing particles sank deep into the snow in minutes. The nadir measurement remained the darkest, but at larger zenith angles, the surface of the contaminated snow changed back to almost as white as clean snow. Thus, for a ground observer the darkening caused by impurities can be completely invisible, overestimating the albedo, but a nadir-observing satellite sees the darkest points, underestimating the albedo. Through a reciprocity argument, we predict that at noon, the albedo perturbation should be lower than in the morning or after-noon. When sunlight stimulates sinking more than melting, the albedo should be higher in the afternoon than in the morning, and vice versa when melting dominates. However, differences in the hydrophobic properties, porosity, clumping, or size of the impurities may cause different results than observed in these measurements.
  • Svensson, Jonas; Virkkula, Aki; Meinander, Outi; Kivekäs, Niku; Hannula, Henna-Reetta; Järvinen, Onni; Peltoniemi, Jouni I.; Gritsevich, Maria; Heikkila, Anu; Kontu, Anna; Neitola, Kimmo; Brus, David; Dagsson-Waldhauserova, Pavla; Anttila, Kati; Vehkamäki, Marko; Hienola, Anca; De Leeuw, Gerrit; Lihavainen, Heikki (2016)
    Soot has a pronounced effect on the cryosphere and experiments are still needed to reduce the associated uncertainties. This work presents a series of experiments to address this issue, with soot being deposited onto a natural snow surface after which the albedo changes were monitored. The albedo reduction was the most pronounced for the snow with higher soot content, and it was observed immediately following soot deposition. Compared with a previous laboratory study the effects of soot on the snow were not as prominent in outdoor conditions. During snowmelt, about 50% of the originally deposited soot particles were observed to remain at the snow surface. More detailed experiments are however needed to better explain soot's effect on snow and to better quantify this effect. Our albedo versus soot parameterization agreed relatively well with previously published relationships.