The Potential For Glacial Flour To Act As Ice Nuclei In Clouds

Abstract

The influence of mineral and dust particles on the immersion freezing mode of ice nucleation has been an area of active research. Most studies focus on dusts from tropical to mid-latitude regions with high latitude dusts remaining mostly unexplored. The goal of this study was to provide an initial evaluation on the ice nucleation efficiency of glacial flour, a natural dust that is common in many high latitude dust source regions. The glacial flour sample used in this study originated from the Findelen Glacier in Switzerland. Surface area and mineral composition analyses were performed and a cold-stage freezer method was used to determine the immersion freezing temperatures of water drops containing glacial flour particles. NX-illite, illite, and kaolinite samples were also tested to verify that the experiment method produced results consistent with previous studies and to be a same-method comparison for the glacial flour. The ice nucleation efficiency of the samples was quantified by using a deterministic approximation to calculate the ice-active surface site density from the freezing temperature and particle surface area data. The glacial flour showed a similar ice nucleation efficiency to NX-illite with a freezing temperature range between -9.6 C and -21.6 C and n_s(T) range between 3.0 x10^{-3} cm^{-2} and 4.1 x 10^0 cm^{-2} These results suggest that the glacial flour sample does not have a particularly high ice nucleation efficiency, but rather falls around mid-range of the pure minerals and natural dusts that have been studied previously. Ranking the importance of the constituents of the glacial flour sample based on both weight percent and surface area percent suggests that the latter may be a better representative of ice nucleation efficiency. Pre-activation could also have an impact on the ice nucleation efficiency of glacial flour, but is only discussed qualitatively here.

Date of Award	31 Dec 2017
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Paul Connolly (Supervisor) & David Schultz (Supervisor)