Dataset associated with "Volcanic ash ice-nucleating activity can be enhanced or depressed by ash-gas interaction in the eruption plume"

Volcanic ash can trigger ice nucleation when immersed in supercooled water, impacting several processes in the eruption plume/cloud and the wider atmosphere upon ash dispersal. The experimental study associated with this dataset explores how interaction with magmatic gases in the hot eruption plume, which inevitably alters the surface properties of ash, may affect the ice-nucleating activity (INA) of ash. We show that the INA of tephra is raised by exposure to H2O(g) mixed with SO2(g) at 800-400 °C, but is substantially reduced by exposure to H2O(g) alone or mixed with HCl(g) at the same temperatures. In contrast, the INA of K-feldspar and quartz is reduced by all three treatments. A decrease in INA after heating with H2O(g) might relate to a loss of ice-active sites by surface dehydroxylation and/or oxidation. On the tephra surfaces, metal chloride or sulphate salts form in the presence of HCl(g) or SO2(g), respectively. While NaCl and CaCl2 seem to have no effect on the tephra INA, CaSO4 is inferred to create ice-active sites, potentially through a particular combination of surface chemistry and topography. Together, these findings suggest a complex interplay of bulk mineralogy and surface alteration in influencing ice nucleation by volcanic ash, and highlight the general sensitivity of ash INA to interaction with gases at high temperatures in the eruption plume.