This project is designed to reconstruct the history of climate in the northwestern United States during the last deglaciation. It includes a field program in Montana and Oregon to collect cores in lakes and bogs, and laboratory analysis of the samples for pollen fossils. These new data will be combined with some existing pollen data in this region to produce maps of the distribution of vegetation throughout this period of rapid climate change. The project will test two hypotheses: 1) that the atmospheric circulation changes induced by the melting of the ice sheet resulted in a time-transgressive sequence of climate change from west to east and from north to south in this region; and 2) that the effects of the summer insolation maximum produced a differential climate response from west to east. The results of this research will provide important climatic boundary conditions in a region where present sample coverage is poor.
