STRATIGRAPHY, IMPURITY AND CRYSTAL PREFERRED ORIETATION IMPACT ON INHOMOGENEOUS DEFORMATION TO LOCATE DISTURBED BASAL ICE
Supervisors: I. Weikusat (AWI, D), M. Dury (Univ. of Ultrecht, NL)
Academic secondments: Univ. of Copenhagen (DK), Univ. of Ultrecht (NL); Non-academic secondments: Schäfter & Kirchhoff GmbH (D), PAGES (CH)
Abstract: The climatic and environmental records in deep ice cores can be challenged when deformation is inhomogeneous and localised eventually leading to disturbances (e.g. folds) affecting the stratigraphy of the ice layers at large depths. Visual stratigraphy provides key information on the existence of such disturbances. The effects on deformation by the presence and interaction of second phases (impurities and air inclusions) with the ice crystals are able to initiate and affect disturbances by e.g. localised flow. However, these effects are poorly understood and thus shall be investigated. On the other hand deformation and thus depending recrystallisation (e.g. grain boundary migration) have the potential to alter original, depositional stratification. ESR 7 will provide the basis for using ice microstructure investigations for advising climate reconstruction through (1) continuous measurements of visual stratigraphy using dark-field method on available ice core material; (2) discontinuous measurements of crystallographic preferred orientations and second phase inclusions; (3) integration with available radio echo sounding data on the large scale; (4) Comparison of the information from (1) to (3) with climate related ice core data (water isotopes, impurities) and evaluation f the information on disturbances in the stratified ice. The envisaged sample material is from EDC provided through sample requests from the BE-OIC Physical Properties consortium.
Key words: ice microstructure, crystal preferred orientation, stratigraphic sequence alteration, flow disturbances, impurity effects on deformation, recrystallisation
Credit: I. Weikusat (AWI)