Electrical charging of snow and ice in polar regions and the potential impact on atmospheric chemistry

Charging of the ice-vapor interface is a well-studied topic in ice physics and atmospheric electrification. However, these effects were not yet considered to examine chemical processes in snow in polar regions because electric potentials at ice surfaces have so far been considered insufficient to initiate chemical reactions and processes. In this review, we analyze literature data to estimate levels of electrification in snow and other frozen objects that can be caused by different processes occurring at the Earth's surface. This analysis demonstrates that threshold values of electric field strength can be exceeded for the appearance of corona discharges and even for the formation of Rayleigh jets due to combined effects of different meteorological and physical processes. The accumulation of electrical charges can lead to different chemical modifications such as electroosmotic phenomena or the accumulation of impurities from the atmosphere in growing ice crystals. Moreover, highly energetic states that occur and dissipate in microseconds as "hot spots" have the potential to initiate free radical processes and even the production of charged aerosols. The review also discusses in detail selected field observations to point out how processes driven by electrical charging may help to interpret these observations, which are at least partly inconsistent with our present understanding of snow and ice chemistry. Finally, some approaches are presented how these effects can be studied in field and laboratory experiments. A further development of this new field at the intersection of ice physics and snow chemistry seems very promising for a better understanding of relevant chemical processes related to the cryosphere. Different processes can lead to high electrical field strengths in snow and ice in polar regions with the potential to initiate free radical processes and a number of other chemical modifications.