The primary goal of this collaborative project between three institutions is to understand the extent and evolution of the Greenland Ice Sheet (GIS) during the Eemian period (roughly 130,000 to 115,000 years ago, the last major interglacial period in Earth's history) and the deglaciation immediately preceding it ("Termination 2"). The GIS is an important agent influencing sea level, and Arctic and global climate, on multiple timescales. Its dynamics need to be understood in the context of past climate changes, but there is little information available about the footprint, volume, and elevation of the GIS prior to the last ice age due to the absence of continuous ice core records prior to 123,000 years ago. During the Eemian, the GIS was perhaps half its present size, contributing on the order of 3 m to "excess" sea level rise. Characterizing the evolution of the GIS during glacial termination 2 and the Eemian would improve our understanding of its dynamics, and enhance our ability to make projections of sea level rise during the coming centuries. Older ice does exist at the bottoms of previously drilled ice cores, but the extraction of age and climate information from this older ice is hampered by the fact that it is stratigraphically disturbed and, in many cases, contaminated with soil or bedrock material. These investigators propose several novel methods to date this disturbed and/or "dirty" ice and to extract information on climate and ice sheet extent. The investigators will combine their new measurements and other available data to develop a more complete history of the GIS during termination 2 and the Eemian. They will work with ice sheet modelers to investigate the constraints that the Eemian data provide for the models and improve their predictive capability. These efforts have the potential to improve our ability to predict the contribution of the GIS to sea-level rise in the coming decades to centuries. Educational and outreach activities include the training of two graduate students, inclusion of this research in summer teacher enrichment programs, a lecture series for graduate students and postdocs, and communication of the results through the news media.