Investigation of the atmosphere-snow transfer process for hydrogen peroxide

Abstract

Of the three primary atmospheric oxidants, hydroxyl radical, ozone, and hydrogen peroxide (H₂O₂), only the latter is preserved in ice cores. To make quantitative use of the ice core archive, however, requires a detailed understanding of the physical processes that relate atmospheric concentrations to those in the snow, firn and thence ice. The transfer processes for H₂O₂ were investigated using field, laboratory, and computer modeling studies. Empirically and physically based numerical algorithms were developed to simulate the atmosphere-to-snow-to-firn transfer processes and these models coupled to a snow pack accumulation model. The models, tested using field data from Summit, Greenland and South Pole, indicate that H₂O₂ is reversibly deposited to the snow surface, with subsequent uptake and release controlled by advection of air containing H₂O₂ through the top meters of the snow pack and temperature-driven diffusion within individual snow grains. This physically based model was successfully used to invert year-round surface snow concentrations to an estimate of atmospheric H₂O₂ at South Pole. Field data and model results clarify the importance of accumulation timing and seasonality in determining the H₂O₂ record preserved in the snow pack. A statistical analysis of recent accumulation patterns at South Pole indicates that spatial variability in accumulation has a strong influence on chemical concentrations preserved in the snow pack.