This proposal is being jointly funded by the Arctic Natural Sciences Program, Antarctic Glaciology Program, and the Paleoclimate Program in the Division of Atmospheric Sciences. The Greenland Ice Sheet Project 2 (GISP2) depth-age scale is accurate within one per cent on an annual basis through the Holocene and into the Wisconsin and therefore has been of great interest to the paleoclimate community. Researchers have used, and want continue to use our most valuable paleoclimate archives, the GISP2 and the Greenland Ice Core Project (GRIP) ice cores, to calibrate chronologies from other materials. Because the GRIP core was drilled simultaneously and in close proximity (30 km) to the GISP2 core, comparison between the two cores was expected to be similar. However, there are segments of the cores where there is sufficient variability and the chronologies have been questioned. This has caused confusion within the ice coring and the paleoclimate communities. An example of these errors can be seen in the Antarctic Siple Dome core. Like the GISP2 chronology, the Siple Dome chronology is based on annual layer counts, but the gas age chronology deeper in the core is based on correlations with the GISP2 record perpetuating the errors that exist in the GISP2 chronology. It is critical that the GISP2 chronology be reexamined and any discrepancies be resolved, if possible. The Principal Investigator will: 1) use new volcanic records obtained since the completion of the original GISP2 depth-age as additional tie points for greater calibration; 2) revise the Holocene portion of the GISP2 depth-age scale based on the new Berylium-10 and Carbon-14 results; and 3) revisit areas of the depth-age scale where discrepancies exist between the GISP2 and GRIP ice cores based on a recent publication. Revision of the GISP2 depth-age scale will be accomplished by reexamining areas of the core that have been identified to be in error by new data that have come available since the completion of the original GISP2 chronology. Additionally, areas of the core where the GISP2 and GRIP chronologies vary will be reexamined. The goal in the cases where discrepancies exist with the GRIP record is not to adjust the GISP2 chronology, but to identify any errors that are now evident due to new data and make adjustments as necessary to obtain the best possible GISP2 chronology.