Sticking deep ice core drills: Why, and how to recover

The GISP deep drill became stuck in 1981, but was free the following year. The NGRIP/EPICA deep drill has suffered from two big setbacks: The drill is stuck both at NGRIP in Greenland and at Dome C in Antarctica. Both events occured in a period with routine drilling and high productivity. The two reasons for the two events are believed to be different, but the chosen bore-hole liquid seems to be problematic. The densifier can adhere to the surface of the ice cuttings, making fine cuttings to sink in the liquid, in spite of a liquid density of 935 kg/m**3. In spite of changed procedures and modified constructions, the drill became stuck again at NGRIP. It was freed using glycol, making use of both the temperature and temparature gradient in the hole.