Recrystallization and deformation mechanisms in the NEEM deep ice core, Greenland

An overview of the deformation and recrystallization mechanisms that are active in the North Greenland Eemian Ice Drilling (NEEM) ice core is given, based on microscale models, light microscopy and cryogenic electron backscatter diffraction (cryo-EBSD). The Holocene ice (0-1419 m depth) deforms by dislocation creep with basal slip accommodated by non-basal slip. The amount of non-basal slip is controlled by the extent of strain induced boundary migration (SIBM). The most important recrystallization mechanisms and processes in the Holocene ice are grain dissection, strain induced boundary migration (SIBM), and bulging nucleation. In the glacial ice (1419-2207 m of depth) basal slip is accommodated by both non-basal slip and grain boundary sliding (GBS). Rotation recrystallization is more important, while SIBM is less important in the glacial ice compared to the Holocene ice. In the Eemian ice (2207-2540 m depth), which is at high temperature, different microstructures occur depending on the impurity content of the ice. The difference in microstructure and deformation mechanisms, between interglacial and glacial ice can have important consequences for ice rheology and ice sheet dynamics.