The Principal Investigators will develop a record of past atmospheric photochemistry, primarily hydrogen peroxide (H2O2), from Greenland snow, firn, and ice. These reconstructed atmospheric records will provide an important data constraint for atmospheric photochemical modeling of past regional and global hydroxyl radical (OH) levels to evaluate the apparent change in atmospheric OH over the past few centuries. Oxidation capacity determines the atmospheric lifetime of many trace chemical species and greenhouse gases. The Principal Investigators will evaluate and validate a model of air-snow exchange using H2O2 as a model compound and the degree of spatial and temporal averaging needed to distinguish statistically significant changes in the concentrations of H2O2 over the past few hundred years. Their approach includes: 1) analysis and synthesis of ice-core data, 2) analysis of prior atmospheric and surface snow data, and 3) modeling of air-snow exchange processes and atmospheric chemistry for interpretation of concentrations in snow, firn, and ice. One previous constraint on the modeling was the lack of availability of co-registered, sub-annual resolution ice-core data for model testing. The Principal Investigators are currently doing continuous analysis on 120-150 m deep cores from four sites in northern Greenland, which will provide excellent data for modeling and will continue these analyses on a new 100-m core from Summit. Another constraint was the lack of availability of year-around records suitable for inferring the deposition and accumulation patterns of snow and chemical species. The 1997-98 winter-over monitoring program at Summit should expand the physically-based model and relate atmospheric and surface snow concentrations to the South Pole data base for model calibration, testing and evaluation. Modeling will continue the framework of physically- based models of air-snow exchange of H2O2 and atmospheric chemistry that the Principal Investigators have developed and tested using data from two sites in Antarctica and preliminary data from Summit. DIARY NOTE
This proposal is overage. It was submitted on April 1 for the April 1, 1998 Arctic Natural Sciences (ANS) deadline. The remaining FY1998 ANS budget was committed to funding a few ANS standard grants and an executive decision was made to hold all of the proposals that were submitted for April 1 for FY1999 funds. In addition, most of the proposals were discussed at the SCICEX panel held on August 5-6, 1998. Due to the heavy travel schedule of our Office of Naval Research (ONR) counterpart, we were unable to meet to discuss which proposals would be transferred to ONR funding until September 23. Our highest priority then was to complete the declinations before they became overage while the uncertainties with the FY1999 budget were being addressed. Further delays in processing this award were due to the co-Principal Investigator transferring from the University of Arizona to Desert Research Institute at the same time that I told Dr. Bales that I was recommending funding of this the proposal.
