Analyses of rates of change in fossil-pollen data from eastern North America reveal that many sites experienced major changes 10,000-13,000 years ago during the last deglaciation and again during the last 1000 years. The PIs propose to expand previous research to several new regions of the northern hemisphere, and to determine the timing, magnitude, and geographic patterns of changes in climate and vegetation during the past 18,000 years in northwestern as well as eastern North America. They will also use a parallel database in Europe to study the patterns and rates of change in Europe over the last 18,000 years, for comparison with North America. Through use of pollen databases for North America and Europe, this research will establish the degree to which rapid vegetation changes in a broad band around the northern hemisphere are synchronous, and will thus identify probable times of major rapid changes in atmospheric circulation. In addition, special attention will be given to a critical site, Lake Tulane, Florida which has a continuous high-resolution pollen stratigraphy extending to at least 45,000 years ago. The pollen stratigraphy from Lake Tulane exhibits major, abrupt changes, which may correlate with as yet poorly understood isotope fluctuations in the Dye 3 Greenland ice core during the period 25,000-55,000 years ago. The results of the research will provide very important data on the nature and extent of global change in the last 20,000 years.
