1. D. Dahl-Jensen, K. Mosegaard, N. Gundestrup, S. J. Johnsen, A. W. Hansen, Niels Bohr Institute for Astronomy, Physics and Geophysics, Department of Geophysics, Juliane Maries Vej 30, DK-2100 Copenhagen OE, Denmark. G. D. Clow, USGS-Climate Program, Box 25046, MS 980, Denver Federal Center, Denver, CO 80225, USA. N. Balling, Department of Earth Sciences, Geophysical Laboratory, University of Aarhus, Finlandsgade 8, DK-8200 Aarhus N, Denmark.