Atmospheric chemical processes and air-snow interactions

H2O2 and HCHO concentrations measured in snowpits and in a shallow core at Siple Dome are presented and discussed in respect topost-depositional processes. Air-firn transfer studies show that physical uptake and release of HCHO and H2O2 by the snow significantlyaffect their concentrations preserved in firn and ice on one hand and atmospheric concentrations on the other hand. Numerical modelssimulating this air-snow transfer successfully reproduce HCHO and H2O2 concentration profiles in snowpits at various Antarctic sites,among other Siple Dome. Sensitivity studies revealed the relative importance of atmospheric concentration, temperature and accumulationrate on the concentrations preserved in ice cores and represent another step towards the quantitative reconstruction of the atmosphericHCHO and H2O2 concentrations and the closely linked oxidizing capacity of the atmosphere based on ice core records. Due to therelatively low accumulation rate and high temperatures at Siple Dome, H2O2 is not well preserved in the firn and ice and drops belowdetection limit with increasing depth. HCHO is low as well, but still above detection limit. The modeling studies and measurements frompits and shallow cores indicate that the Inland Ice core would have the potential to become the best Antarctic HCHO and H2O2paleoclimate record.