This award represents one element of the second Greenland Ice Sheet Project (GISPII). This investigation will focus on the stratigraphy, relaxation characteristics and crystalline structure of ice cores from the GISP II deep drilling at the Summit site, Greenland. Studies will include: 1) delineation of annual layering, 2) precision density measurements to monitor the relaxation characteristics of ice cores as they age, 3) determination of the principal mechanisms by which cores relax, 4) crystal size measurements as a function of the depth and age of the ice, 5) c-axis fabrics measurements, and 6) analysis of debris in basal ice cores. Relaxation of ice results in significant changes in their mechanical condition that must be considered in relation to the preparation and analysis of core samples for entrapped gas and chemical studies; c-axis fabrics constitute the primary source of information for interpreting the strain history of the ice column that vertically drilled cores represent. Accordingly, very careful documentation of these key properties of summit site ice cores is essential if we are to accurately assess the depth - age relationship of deep cores and have confidence in paleoclimate reconstructions based on geochemical and entrapped gas analysis of these cores.
