Can we model snow photochemistry? Problems with the current approaches.

Area of Science:

• Atmospheric Chemistry
• Environmental Science
• Physical Chemistry

Background:

• Snow is a significant photochemical reactor in polar regions, influencing tropospheric composition.
• Existing snow photochemistry models often assume reactions occur in a liquid brine layer on ice surfaces.

Purpose of the Study:

• To critically evaluate the assumptions underlying current snow photochemistry models.
• To investigate the location and reactivity of impurities within snowpack.

Main Methods:

• Analysis of ice crystal surface structure and impurity-ice interactions.
• Examination of impurity distribution and reactivity in different snow media.
• Critique of existing snow photochemistry modeling approaches.

Main Results:

• Impurities form brine only in grain boundary grooves, not uniformly on ice surfaces, due to poor ice wettability.
• Reactions in snow likely occur on ice surfaces or within particulate matter (e.g., organic particles), not in bulk liquid brine.
• Current models may fit observations due to adjustable parameters rather than accurate representation of snow chemistry.

Conclusions:

• The assumption of a liquid brine medium in snow photochemistry models is questionable.
• Developing accurate, predictive snow chemistry models without adjustable parameters is a major challenge.
• Future modeling efforts may benefit from focusing on environments with minimal organic particle influence, like the East Antarctic plateau.