Firn Properties and Processes at Shallow Coring Sites in Greenland

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The proposed project examines physical processes that affect the manner in which heat, vapor, and chemical species in air are incorporated into snow and polar firn. The processes include diffusion and advection, the transport of heat, vapor, and chemical species by air flow within snow and firn. An understanding of these processes is important because they control grain growth, snow metamorphism, and the rate at which chemical species in the atmosphere become incorporated into the snow and firn, and thus will affect interpretation of polar ice core data. The objectives of the project are to define the magnitude and extent, both in space and time, of these transfer processes, and to develop a process-level understanding and modeling capability of the phenomena within the snow and firn. The approach is to conduct field studies at sites where shallow cores and meteorological data are being obtained on the Greenland Ice Sheet to determine the spatial and temporal extent fro key parameters, and boundary conditions needed to model the conduction and advection of heat, mass and chemical species within the firn. An existing multidimensional numerical model is being expanded to simulate the processes and serve as the basis for ongoing and future work in transport and distribution of chemical species. Currently interpretation of the polar ice core data assumes that diffusion controls the rate at which chemical species are incorporated into the firn. The proposed project will determine the site-specific extent of ventilation in the firn, and will provide a model for multidimensional diffusion and ventilation on grain growth, sublimation rates, and chemical species transport.