Microstructure in the EastGRIP ice core, Greenland

Behavior of Earth’s ice sheets is intensely monitored via surface and remote sensing techniques to improve predictions of sea level evolution. Radio echo sounding along with drilling ice cores are currently used to monitor the Earth’s ice sheets behaviour not only from the surface but in the 3rd dimension. Particularly the ice material properties can only be accessed via ice drilling. These properties control the deformation in general, and particularly strain localization such as observed in ice streams, which supply the major discharges into the oceans. Currently the first ice core on an active ice stream, the North-East Greenland Ice Stream (NEGIS) is being drilled. EastGRIP (East Greenland Ice-Core Project, http://eastgrip.org) drilling started in 2016 and will be ongoing until 2019. This is the first chance to study ice microstructure from a dynamically active region (www.awi.de/en/focus/eisschilde/eis-ist-ein-heisses-material.html), with a deformation regime differing from the usual locations of previous long ice cores. Those were usually placed on domes or on ice divides due to straightforward kinematics and deformation rates which is advantageous for paleo-climate reconstruction from ice core records. We present CPO (c-axes fabric) and the grain size measurements of the uppermost 350m, the depth to which the ice core has been processed for analysis so far (275 thin sections discontinuous with 10m depth resolution). The CPO patterns found in the upper 350m at EastGRIP show (1) a more rapid evolution of c-axes anisotropy with depth compared to other ice cores and (2) partly novel characteristics in the caxes distributions. (Remark: This is an invited poster.