This is one of four coordinated projects that will make use of the camp facilities established on the ice sheet in the interior of Greenland as part of the GISP-2 ice core drilling effort, in order to investigate how atmospheric trace elements are deposited on the ice and what kind of changes they undergo as they are being incorporated into the ice. An understanding of such processes is necessary in order to properly interpret the proxy climate data that can be recovered from ice cores. While significant progress has been made recently in extracting and analyzing ice cores, progress in understanding the air to snow transfer process for reactive chemical species has lagged behind. The major goal of this project is to understand the reasons for changes in the composition of snow at or near the surface of the Greenland ice sheet that are observed to occur within days or weeks after deposition. It is known that the concentration of soluble ionic species and aerosol-associated species may change rapidly with time, but the variability may be masked by small-scale spatial heterogeneity. A sampling protocol will be set up to characterize the spatial variability on the one meter to one kilometer scale. Beryllium-7, a naturally-occurring radionuclide that is formed in the stratosphere, will be used as an indicator for small aerosol particles. Its close association with atmospheric particulates and half-life of 53 days make it a useful tracer of the incorporation of aerosols in the snow and their post-depositional redistribution within the snowpack
