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.
- Pub Date:
- Hydrology, Environmental Sciences, Physics: Atmospheric Science