The Microstructural Location and Effects of Impurities in Polar Ice Cores

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This award supports a project to fully characterize the microstructure in ice cores, in particular the microstructural locations of impurities, defect structures and strain gradients. This work will complement the optical observations, electrical conductivity measurements, and precise, detailedmeasurements of the soluble ion and gas contents that are performed by others. The project will use both scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) and scanning confocal optical microscopy coupled with Raman spectroscopy (RS) to determine the microstructural locations of impurities and correlate this information with depth/age, and impurity type and concentration for several polar ice cores from different locations, different elevations, and different meteorological conditions (precipitation, temperature. The broader impacts of the proposed work are that knowledge of the location of impurities and the defect structures in the ice, and their effects on the local mechanical and physical properties, will allow paleoclimatologists to better interpret ice core data and other scientists to understand and model the physical and mechanical properties of natural ice sheets. Other broader impacts are that the project will lead to the education of a Ph.D. student, who will gain experience in ice specimen preparation and characterization, scanning electron microscopy, x-ray microanalysis, Raman spectroscopy, electrical measurements and mechanical testing, as well as the knowledge gained from coursework. The work will also be performed by a number of undergraduates, typically two per year. In addition to publishing results from the research in refereed journals and presenting them at conferences, key data will be placed on a web page: http://www.dartmouth.edu/~ianbaker/Ice/ice.html