Paleoecological Evidence of W&G1999 and Sub-W&G1999 Climate Variations
in the Western U.S. During the Late Quaternary.
Cathy Whitlock and Laurie D. Grigg (1999),
IN: Mechanisms of Global Climate Change at Millennial Time Scales.
R.S. Webb, P.U. Clark, and L.D. Kaigwin (Editors)
American Geophysical Union Monograph. p 227-241
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Figure 1. Paleoclimatic records referred to in the text. 1=Pilot Mill, 2=Cape Ball, 3=Pleasant Island, 4=Crowfoot Lake, 5=Marion Lake, 6=Dashwood, 7=Bogachiel River, 8=Kalaloch Sea cliffs, 9=Humptulips Bog, 10=Davis Lake, 11=Carp Lake, 12=Battle Ground Lake, 13=Fargher Lake, 14=Little Lake, 15=Yellowstone lakes, 16=Sky Pond, 17=Pyramid Lake, 18=Clear Lake, 19=Mono Lake, 20= Owens Lake, 21=Searles Lake, 22=Santa Barbara Basin, 23=Walker Lake, 24=Deadman Lake, 25=Potato Lake, 26=Hay Lake, 27= Guaymas Basin. |
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Figure 2. Comparison of W&G1999-time scale controls of climate change (July insolation anomalies at latitude 45° N and global ice volume) and pollen data from Carp Lake, Washington (Whitlock and Bartlein, 1997), Clear Lake, California (Adam, 1988), and Grande Pile, France (Woillard and Mook, 1982) over the last 130 kyr. The Carp Lake data are a smooth record of the ratio of Pseudotsuga + Quercus + Cupressaceae pollen to Picea pollen to indicate warm and cold vegetation types. High percentages of Quercus at Clear Lake indicate warm dry conditions, and at Grande Pile high values of arboreal to nonarboreal pollen (AP/NAP) indicate periods of forest. |
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Figure 3. Changes in arboreal/nonarboreal pollen ratios (AP/NAP) and Picea percentage data at Carp Lake, Washington, at the time of Heinrich events. The graphs show the pollen values in the 5000 years before (negative values and after (positive values) H0 through H6. Diamonds denote the position of calibrated radiocarbon dates (Whitlock and Bartlein, 1997). High AP/NAP values indicate periods of greater forest cover during H4, H5, and H6, whereas steppe vegetation prevailed at the time of H0, H1, H2, and possibly H3. The smoothed curves are drawn with a lowess procedure (Cleveland, 1993). Picea percentages are plotted to show warm periods at the top of each graph. Warm conditions (based on changes in Picea percentages) immediately follow H1, H2, and possibly H3 (see text for discussion). |
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Figure 4. Summary of the vegetation and climate history for MIS 2 and 3 from ten sites in the Pacific Northwest. Shading shows intervals of sub-W&G1999 climate change that coincide with the timing of Heinrich events in the North Atlantic (shown on right side of figure). |
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Figure 5. Late-glacial pollen percentages and charcoal accumulation rates from Little Lake, OR (based on Grigg and Whitlock, 1998). Open curves are a five-fold exaggeration of black curves. In Pinus curve hatched lines show abundance of Pinus monticola-type. Interval A is the increase in P. monticola associated with YD cooling. Interval B shows the establishment of Pseudotsuga after a peak in charcoal accumulation. The radiocarbon age scale was derived using the CALIB 3.0 calibration program (Stuiver and Reimer, 1993). |
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Figure 6. Fire occurrence during 500-year periods in Yellowstone National Park, based on high-resolution charcoal data from two lakes in different regions. The charcoal accumulation rates were transformed to standard z scores and plotted at the center of 500 year periods. Each 500-year period is offset by 250 years (Millspaugh, 1997). Note that there are several periods when fires occurred in both regions co-occur suggesting a large-scale climate control. |