Electrical conductivity measurements from the GISP2 and GRIP Greenland ice coresNature, 366, p. 549-552, 1993.
Box 60220, Desert Research Institute, University of Nevada, Reno, Nevada 89506, USA.
C.U. Hammer, H.B. Clausen, D. Dahl-Jensen and N.S. Gundestrup
Geofysisk Afdeling, Niels Bohr Instituttet for Astronomi, Fysik og Geofysik, Københavns Universitet
The direct-current conductivity of glacial ice depends on its acidity, and can also indicate changes in climate, as ice formed in cold, dusty periods has a high concentration of alkaline dust, which significantly reduces the conductivity compared to warmer, less dusty periods. Here we present electrical conductivity records for the Greenland Ice Sheet Project 2 (GISP2) and Greenland Ice-core Project (GRIP) ice cores, drilled 28 km apart to enable direct comparison of the results. The upper parts of both records are consistent with previous evidence from other Greenland cores for a stable Greenland climate during the Holocene, and a series of warm events punctuating the last glacial period. However, there is a significant discrepancy between the two records in the bottom 10% of the cores, calling into question recent reports of climate variability in the last intergiacia1 and the penultimate glaciation. At this stage, it is too early to say what exactly is causing the discrepancy, although ice flow may have introduced some discontinuities into the records. Further work will be necessary to establish how much climatic information it will eventually be possible to extract from the lower parts of the two cores.