Past temperatures directly from the Greenland ice sheet.

Science, Vol. 282, p. 268-271, Oct. 1998

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

A Monte Carlo inverse method has been used on the temperature profiles measured down through the GRIP borehole at the Summit of the Greenland Ice Sheet and the Dye 3 borehole 865 km farther south. The result is a 50,000 year long temperature history at GRIP and a 7,000 year history at DYE 3. The Last Glacial Maximum (LGM), the Climatic Optimum, the Medieval Warmth, the Little Ice Age (LIA) and a warm period at 1930 AD are resolved from the GRIP reconstruction with the amplitudes -23 K, +2.5 K, +1 K, -1 K, +0.5 K respectively. The Dye3 temperature is similar to the GRIP history but has 1.5 times larger amplitudes indicating higher climatic variability there. The calculated terrestrial heat flow density from the GRIP inversion is 51.3 mW/m