Cosmogenic Radionuclide in Ice Cores

This project is intended to provide a record of cosmogenic radionuclides, 10Be (half-life = 1.5 Myr) and 36Cl (0.30 Myr), concentrations in the Siple Dome ice cores. It is particularly instructive to compare the Antarctic record with the detailed Arctic record that we are measuring as part of the GISP2 project.

We cut annual samples of the "A" core from the surface to 48 m corresponding to the years 1995 AD to 1698 AD. The 10Be measurements have been nearly completed. The 36Cl chemistry was completed at Berkeley. AMS 36Cl measurements and Cl concentration measurements at LLNL are still unfinished. Below 54 m, we coordinated our sample collection with the continuous ion measurements. Although we received more than 800 melt water samples, more than 25% of these samples were not suitable for our work, either because of partial loss of solution during transport, unclear depth information, or because the sample mass was too small. We have selected over 600 samples, including some uncertainties of sample documentation that cover less than 75% of total depth of core. Presently, chemical separation and purification of Be and Cl for all samples has been completed. 10Be AMS measurements are also nearly completed. Although Cl sample preparation has been completed, about 90% of the 36Cl measurements and Cl concentration measurements at LLNL need to be performed. Thus, the data are still preliminary and fragmental.

Each melted ice sample was passed through a 30 µm Millipore filters before chemical separation of Be and Cl. A photograph of each filter was taken and digitized for archival storage. These digitized pictures will be available for distribution to other investigators.

This material is based upon work supported by the National Science Foundation under Grant No. OPP-0126343.