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UP: Fachverband Umweltphysik

UP 2: Clouds and Aerosols

UP 2.3: Talk

Thursday, September 2, 2021, 14:35–14:50, H3

Cracking the problem of atmospheric ice nucleation: chemically induced fracturing of alkali feldspar makes it a better ice-nucleating aerosol particle — •Tilia Gädeke¹, Alexei Kiselev¹, Alice Keinert¹, Thomas Leisner¹, Christoph Sutter², Elena Petrisheva³, and Rainer Abart³ — ¹KIT, IMK-AAF, Karlsruhe, Germany — ²Universität Heidelberg, IFU, Heidelberg, Germany — ³University of Vienna, Department of Lithospheric Research, Vienna, Austria

Feldspar is a major constituent of magmatic, metamorphic, and sedimentary rocks on the Earths* surface. Consequently it is also an abundant constituent of the solid aerosol particles and induces heterogeneous freezing in cloud droplets. The freezing process changes cloud properties and precipitation formation. The mineralogy of feldspar has a crucial effect on its ability to induce freezing of water. The mechanisms relating the microstructure of feldspars and enhanced ice nucleation (IN) efficacy are not known and are currently debated.

The particularly high IN activity of alkali feldspar has been attributed to structural similarities between specific prism planes of ice and feldspar. In this study, the gem quality K-rich alkali feldspar was shifted towards more Na-rich compositions. The cation exchange induces parallel cracks with an orientation close to (100). Droplet freezing assay experiments performed on the cation-exchanged feldspars, revealed an increase of freezing efficacy with respect to the untreated feldspar. This contribution demonstrates how the natural complexity of rock-forming minerals can have a direct impact on Earth's climate.