Sticking deep ice core drills: Why and how to recover 

Memoirs of National Institute of Polar Research, Special Issue, No. 56, p. 181-195, 2002 

N.S. Gundestrup, S.J. Johnsen, S.B. Hansen
epartement of Geophysics, The Niels Bohr Institute of Astronomy, Physics and Geophysics, University of Copenhagen.
H. Shoji
Kitami Institute of Technology, 165, Koencho, Kitami 090-8507, Japan.
P. Talalay
Department of Descriptive Geometry, St. Petersburg State Mining Institute, 21 Line, 2, 199026 St. Petersburg, Russia.
F. Wilhelms
AWI, Colombusstrasse, Bremerhaven, Germany.

ABSTRACT.
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 occurred in a period with routine drilling and high productivity. The reason 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 ice cuttings to sink in the liquid, in spite of a liquid density of 935 kg/m³. In spite of changed procedures and modidied constructions, the drill became stuck again at NGRIP. It was freed using glycol, making use of both the temperature and temperature gradient in the hole.