HR: 1330h
AN: PP32B-0294    [PDF]
TI: Development of Modern Analogue and Mutual Overlap Techniques for Paleoclimatic Reconstructions and Model Validation from Plant Macrofossil Assemblages in North America
AU: * Thompson, R S
EM: rthompson@usgs.gov
AF: U.S. Geological Survey, Box 25046, MS 980 Denver Federal Center, Denver, CO 80225 United States
AU: Anderson, K H
EM: katherine.anderson@colorado.edu
AF: University of Colorado, Institute for Arctic and Alpine Research, 1560 30th Street, Boulder, CO 80309 United States
AU: Strickland, L E
EM: lstrickland@usgs.gov
AF: U.S. Geological Survey, Box 25046, MS 980 Denver Federal Center, Denver, CO 80225 United States
AU: Bartlein, P J
EM: bartlein@uoregon.edu
AF: University of Oregon, Department of Geography, Eugene, OR 97403 United States
AU: Shafer, S L
EM: sshafer@usgs.gov
AF: U.S. Geological Survey, 200 SW 35th Street, Corvallis, OR 97333 United States
AB: Plant macrofossils provide a unique resource in paleoclimatology: They can usually be identified to the species level, can be directly dated by radiocarbon analysis, and can be related to modern living relatives whose ranges are usually well-known. Fossil packrat middens provide a spatially and temporally rich data set of well-dated species-level plant macrofossil assemblages covering the last glacial period and the Holocene in western North America. Other plant macrofossil assemblages are available from permanently wet (e.g., lakes, mires) and permanently dry (e.g., cave sediments) deposits. To provide the basis for exploring the paleoclimatic implications of these macrofossil assemblages we have investigated the present-day relations between climatic parameters and the distributions of more than 600 woody plant species across North America, based on a 25-km grid of climatic, bioclimatic, and species distribution data. We used this data set to explore the efficacy of climatic estimation from plant assemblages based on the "modern analogue" comparison between the target plant assemblage and all other plant assemblages in the modern data set using the Jaccard similarity coefficient. The estimates produced by these methods were then compared with the range of permissible climates for each assemblage based on the mutual overlap approach. Our explorations suggest that the "modern analogue" method provides meaningful climatic estimates in most regions, if the number of species in the target assemblage is large enough. Although it is pleasing to obtain a single value for each climatic parameter associated with a given macrofossil assemblage, it is also potentially misleading in that the range of permissible climates for the assemblage may be large, particularly under atmospheric carbon dioxide concentrations different from those of today. The mutual overlap approach may provide a more realistic view of the past and may be better suited for data - model comparisons.
DE: 1699 General or miscellaneous
DE: 4255 Numerical modeling
DE: 4299 General or miscellaneous
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting