This proposed work concerns the development of a history of the oxidation capacity of the atmosphere over approximately the past two hundred years by measuring and interpreting the hydrogen peroxide, formaldehyde, and nitric acid concentrations in the snow and firn at South Pole station. The primary goal is to develop a record of past atmospheric photochemistry, with a secondary goal of evaluating the degree of spatial or temporal averaging necessary to resolve statistically significant changes in the concentration of these species over the past 200 years. The proposed approach involves year-round sampling of air and near-surface snow, summer sampling and analysis of snow pits and firn cores, and modeling the air-snow chemistry in order to interpret the observed concentrations in the firn. South Pole station is ideal for this work because the extreme cold makes the chemistry relatively simple, the NOAA Climate Modeling and Diagnostics Laboratory provides a context of high quality meteorological and chemical data, and the year-round occupation of the station makes year-round sampling possible.
Intensive sampling during the austral summer will be done in two snow pits around the perimeter of the snow stake field (for accumulation observations). Proximity to the stake field is important in order to maintain time control for stratigraphic and chemical horizons and markers.
The modeling program will expand on the framework of physically based models of the air-snow exchange of hydrogen peroxide developed and tested by the principal investigator during earlier work at South Pole and in central Greenland. ***
