Atmospheric ice nuclei in the Eyjafjallajökull volcanic ash plume

Abstract

Abstract.We have sampled atmospheric ice nuclei (IN) and aerosol in Germany and in Israel during spring 2010. IN were analyzed by the static vapor diffusion chamber FRIDGE, as well as by electron microscopy. During the Eyjafjallajökull volcanic eruption of April 2010 we have measured the highest ice nucleus number concentrations (>600 l −1 ) in our record of 2 yr of daily IN measurements in central Germany. Even in Israel, located about 5000 km away from Iceland, IN were as high as otherwise only during desert dust storms. The fraction of aerosol activated as ice nuclei at −18 • C and 119 % rh ice and the corresponding area density of ice-active sites per aerosol surface were considerably higher than what we observed during an intense outbreak of Saharan dust over Europe in May 2008.Pure volcanic ash accounts for at least 53-68 % of the 239 individual ice nucleating particles that we collected in aerosol samples from the event and analyzed by electron microscopy. Volcanic ash samples that had been collected close to the eruption site were aerosolized in the laboratory and measured by FRIDGE. Our analysis confirms the relatively poor ice nucleating efficiency (at −18 • C and 119 % ice-saturation) of such "fresh" volcanic ash, as it had recently been found by other workers. We find that both the fraction of the aerosol that is active as ice nuclei as well as the density of ice-active sites on the aerosol surface are three orders of magnitude larger in the samples collected from ambient air during the volcanic peaks than in the aerosolized samples from the ash collected close to the eruption site. From this we conclude that the ice-nucleating properties of volcanic ash may be altered substantially by aging and processing during long-range transport in the atmosphere, and that global volcanism deserves further attention as a potential source of atmospheric ice nuclei.

Deposition and immersion-mode nucleation of ice by three distinct samples of volcanic ash

“…Unlike field measurements, however, it has been suggested that all volcanic ash may have similar ice nucleation efficacy, initiating ice formation in a relatively narrow temperature range of approximately 250 to 260 K (Durant et al, 2008); however, these works are difficult to interpret quantitatively, especially in cases where the nucleation mode is unclear, frozen fractions are unavailable, or the available surface area has not been quantified. More recently, several studies have investigated the deposition-and/or immersion-mode ice nucleation properties of ash from the 2010 eruption of the Eyjafjallajökull volcano in Iceland (Steinke et al, 2011;Hoyle et al, 2011;Bingemer et al, 2012). The results of these studies, combined with previous studies on large, 250-300 µm ash particles from the 1980 Mt.…”

Anthropogenic radionuclides in atmospheric air over Switzerland during the last few decades

“…Seifert et al 51 showed the existence of very efficient IN during the Eyjafjallajökull volcanic event. Bingemer et al 52 also observed a large increase of the IN concentration during this event, with IN surface densities of at least a factor two higher than that in other conditions (for example, air masses affected by mineral dust). Seifert et al 51 demonstrated the presence of ash-assisted formation of cirrus-like clouds in the troposphere over Leipzig and Maisach during several days after the first observational period (14-17 April 2010).…”

Effects of crystallographic properties on the ice nucleation properties of volcanic ash particles

“…These results (Figure 3) indicated that ash particles might not act as efficient IN in deposition mode, but within the volcanic plume where ash concentrations greatly exceed background mineral dust concentrations their role in glaciating clouds would be important. We suggest that the reason volcanic ash particles investigated by previous studies [Schnell and Delany, 1976;Schnell et al, 1982;Hoyle et al, 2011;Steinke et al, 2011;Bingemer et al, 2012] were poor IN is because these ash particles may lack the necessary crystalline structural properties; however, further characterization of these ash particles is necessary to confirm the role of crystallinity toward ice nucleation.…”

“…On the other hand, Langer et al [1974] suggest that H 2 SO 4 produced from SO 2(g) oxidation associated with ash particles could reduce ice-forming efficiency, which lead to the conclusion that volcanic ash could be a poor source of atmospheric IN [Schnell and Delany, 1976;Schnell et al, 1982]. More recently, Bingemer et al [2012] found that ash particles collected near the eruption site were less efficient at À18°C and 119% relative humidity with respect to ice conditions in inducing ice nucleation compared to ambient particles collected in central Germany about 2200 km away from the eruption event. More specifically, Steinke et al [2011] observed that ice nucleation efficiency of ash particles is poorer than Arizona test dust (ATD; a commonly used proxy mineral for natural atmospheric mineral dust [e.g., Murray et al, 2012]) particles.…”

“…More specifically, Steinke et al [2011] observed that ice nucleation efficiency of ash particles is poorer than Arizona test dust (ATD; a commonly used proxy mineral for natural atmospheric mineral dust [e.g., Murray et al, 2012]) particles. Further, Hoyle et al [2011] investigated ice nucleation efficiency of ash particles from the same volcanic eruption event that Bingemer et al [2012] and Steinke et al [2011] studied and found that ash particles were poor IN in the deposition mode at warmer temperatures only. However, these studies also showed that volcanic ash particles are more efficient than both Asian and Saharan dust particles.…”