Beryllium 10 in the Greenland Ice Core Project ice core at Summit, Greenland

Abstract

Concentrations of the cosmogenic isotope 10 Be have been measured in more than 1350 samples from the Greenland Ice Core Project (GRIP) ice core drilled at Summit, Greenland. Although a dust‐associated component of 10 Be retained by 0.45 μm filters in some of the samples complicates the interpretations, the results confirm that the first‐order origin of 10 Be concentration variations is changes in precipitation rate associated with different climate regimes. This effect is seen not only between glacial and interglacial periods, but also during the shorter “Dansgaard‐Oeschger” interstadials. By contrast, the 10 Be data do not support the interpretation of rapidly varying accumulation (i.e., climate) during the last interglacial. They can, however, be used to help place limits on the origin of the ice in these events. After taking into account variable snow accumulation effects, variations in the 10 Be flux are observed, probably caused by solar and geomagnetic modulation, but possibly also by primary cosmic ray variations. The most dramatic is a 10 Be peak ∼40,000 years ago, similar to that found in the Vostok ice core, thus permitting a very precise correlation between climate records from Arctic and Antarctic ice cores. The 36 Cl/ 10 Be ratio (considering either “total” or only ice‐associated 10 Be) shows significant variability over the whole core depth, thus confirming the difficulty in using this parameter for “dating” ice cores.