Impacts of erupted and resuspended volcanic ash from the 2010 Eyjafjallajökull eruption, Iceland, on atmospheric ice-nucleating particle concentrations

Volcanic ash can act as ice-nucleating particles (INPs), which by triggering freezing of supercooled water droplets in the atmosphere, can profoundly influence clouds and thereby climate [1]. Volcanoes worldwide sporadically emit large amounts of ash into the atmosphere including at middle to high latitudes (30-90° N/S) where, importantly, other major types of INPs such as windblown Saharan dust from low latitudes are less abundant. A recent study found that windblown Icelandic dust of volcanic and glacio-fluvial origin could episodically dominate INP concentrations between 3 to 5.5 km above sea level over the North Atlantic and Arctic [2]. However, it remains unexplored how volcanic ash emissions from explosive eruptions, which typically occur every 3 to 5 years in Iceland, affect INP concentrations in these regions. Here we investigated the Eyjafjallajökull eruption from 14 April to 22 May 2010 and Eyjafjallajökull ash resuspension events (by wind) thereafter as sources of INPs to the atmosphere. Specifically, by combining ash concentration and temperature data from Lagrangian particle dispersion model simulations (Numerical Atmospheric dispersion Modelling Environment [3]) with a laboratory-derived parameterisation of the ice-nucleating activity of this ash [2,4-5], we calculated INP concentrations up to 10 km above sea level across the Northern Hemisphere during and following the Eyjafjallajökull eruption. In late April 2010, the erupted ash produced INP concentrations >0.01 L^-1 (potentially capable of affecting cloud liquid water content) in up to ~14 vol% of air masses at temperatures between 0 and -35 °C and latitudes between 45 and 90° N. In contrast, the contribution of resuspended ash to the atmospheric INP population in subsequent months was up to several orders of magnitude smaller, partly because resuspended ash particles more seldomly reached altitudes where temperatures were low enough for ice nucleation. Findings of this case study and perspectives on further integrating model and laboratory data to improve understanding of the impacts of volcanic ash on clouds and climate will be discussed.

[1] Murray, B. J., Carslaw, K. S, Field, P. R. (2021) Atmospheric Chemistry and Physics, 21, 665-679, doi:10.5194/acp-21-665-2021.

[2] Sanchez-Marroquin, A., Arnalds, O., Baustian-Dorsi, K. J., Browse, J., Dagsson-Waldhauserova, P., Harrison, A. D., Maters, E. C., Pringle, K. J., Vergara-Temprado, J., Burke, I. T., McQuaid, J. B., Carslaw, K. S., Murray, B. J. (2020) Science Advances, 6, eaba8137, doi:10.1126/sciadv.aba8137.

[3] Jones, A., Thomson, D., Hort, M., Devenish, B. (2007) In: Borrego, C., Norman, A.-L. (Eds) Air Pollution Modelling and its Application XVII, Springer, Boston, 580-589, doi:10.1007/978-0-387-68854-1_62

[4] Hoyle, C. R., Pinti, V., Welti, A., Zobrist, B., Marcolli, C., Luo, B., Höskuldsson, Á., Mattsson, H. B., Stetzer, O., Thorsteinsson, T., Larsen, G., Peter, T. (2011) Atmospheric Chemistry and Physics, 11, 9911-9926, doi:10.5194/acp-11-9911-2011.

[5] Steinke, I., Möhler, O., Kiselev, A., Niemand, M., Saathoff, H., Schnaiter, M., Skrotzki, J., Hoose, C., Leisner, T. (2011) Atmospheric Chemistry and Physics, 11, 12945-12958, doi:10.5194/acp-11-12945-2011.