The cutting and flow properties of ice depend strongly on its physical properties, as e.g. crystallite size, shape and fabrics. As the crystallites properties depend on the geochemical impurity and dust load, as well as the ice flow, and thus vary with depth,the cutting behaviour when drilling an ice core will change with depth. We are at the beginning of systematic tests and we will present first qualitative observations and links between cutting size, core production, and ice properties.The EPICA (European Project for Ice Coring in Antarctica) borehole in DML (Dronning Maud Land, Antarctica) was under-balanced by about three bars its bottom over two years. We found that the borehole closure strongly correlates with the crystallite size record as observed in the ice core. We will discuss this as an illustrative example and suggest to leave bore holes slightly under-balanced for a while to determine the flow properties of ice sheet directly from borehole closure.
Helmholtz Research Programs > MARCOPOLI (2004-2008) > POL6-Earth climate variability since the Pliocene