Continuous high-resolution pollen data for the past 225 ka from sediments in Bear Lake, Utah-Idaho reflect changes in vegetation and climate that correlate well with variations in summer insolation and global ice-volume during MIS 1 through 7. Spectral analysis of the pollen data identified peaks at 21-22 and 100 ka corresponding to periodicities in Earth's precession and eccentricity orbital cycles. Suborbital climatic fluctuations recorded in the pollen data, denoted by 6 and 5 ka cyclicities, are similar to Greenland atmospheric temperatures and North Atlantic ice-rafting Heinrich events. Our results show that millennial-scale climate variability is also evident during MIS 5, 6 and 7, including the occurrence of Heinrich-like events in MIS 6, showing the long-term feature of such climate variability. This study provides clear evidence of a highly interconnected ocean-atmosphere system during the last two glacial/interglacial cycles that extended its influence as far as continental western North America. Our study also contributes to a greater understanding of the impact of long-term climate change on vegetation of western North America. Such high-resolution studies are particularly important in efforts of the scientific community to predict the consequences of future climate change.
Bibliographical noteFunding Information:
We particularly thank individuals at the USGS, NSF, ICDP and DOSECC for their contributions in core collection. Sample material used in this project was provided by LacCore (the National Lacustrine Core Repository at the Limnological Research Center, University of Minnesota, Minneapolis, USA), and collected by D. Kaufman, with partial funding for sample collection provided by the USGS. We especially thank D. Kaufman, but also J. Bright, R. Alley, L. Scuderi, R. Y. Anderson, C. Tzedakis, W. Dean, C. Whitlock and P. Bartlein for helpful comments on this manuscript; W. Dean for providing XRD data; J. Bright for the isotope data; S. Colman for providing the chronology; and J. New and H. Abdul-Aziz for helping with the spectral analysis. GJM's research was supported by a postdoctoral grant from the Universidad de Granada (Spain) Laboratory of Paleoecology Contribution No. 104.
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