HR: 16:00h
AN: B44C-01    [Abstracts]
TI: Comparison of Holocene fire-history records from temperate latitudes of western North and South America
AU: * Whitlock, C
EM: whitlock@montana.edu
AF: Montana State University, Dept. Earth Sciences, Montana State Univ., Bozeman, MT 59717
AU: Bartlein, P J
EM: bartlein@uoregon.edu
AF: University of Oregon, Dept. Geography, Univ. Oregon, Eugene, OR 97403
AU: Markgraf, V
EM: vera.markgraf@colorado.edu
AF: University of Colorado, INSTAAR, Box 450, Univ. Colorado, Boulder, CO 80309
AU: Bianchi, M M
EM: mariam@bariloche.com.ar
AF: CONICET-CRUB, Universidad Nacional del Comahue, Quintral 1250, Bariloche, 8400 Argentina
AU: Marlon, J
EM: jmarlon@uoregon.edu
AF: University of Oregon, Dept. Geography, Univ. Oregon, Eugene, OR 97403
AB: During the last 20 kyr, fire-history records from the western U.S. and Patagonia display similar patterns and timing despite differences in the large-scale controls of climate between the two hemispheres. In summer-dry areas of northwestern North America, charcoal levels rise after 12 ka and the distribution of charcoal peaks indicates higher-than-present fire frequency until ca. 5-7 ka. High fire occurrence is attributed to environmental changes arising from the amplification of the seasonal cycle of insolation in the early Holocene, including the enhancement of the subtropical high-pressure system and increased summer drought. In Patagonia, charcoal records from lat 40-46S, and south of lat 50S also registered high fire activity between 12 and 6-8 ka, a time when summer insolation was less than at present but winter insolation was greater than at present. High fire occurrence may be explained by the location of winter and summer storm tracks between lat 46 and 50S, an earlier fire season due to warmer winters, and a pattern of interannual variability that favored recurring drought in the early Holocene. Comparable to the Rio Rubens record at lat 52S (Huber et al. 2004), L. Pollux, Chile (45.6917S, 71.6917W) records high fire frequency associated with parkland vegetation. L. Trebol (Lat. 41.07125S, Long. 79.4161W) farther north also features frequent fires during a parkland period and later with the expansion of {\it Nothofagus-Austrocedrus} woodland. In all three sites, the fire frequency declined with the development of closed {\it Nothofagus} forest in the late Holocene. The synchroneity in fire activity patterns in the two hemispheres is consistent with that observed in other terrestrial paleoclimate records from the mid- and high latitudes. It suggests that the proximal controls of fire occurrence on millennial time scales are ultimately driven by insolation and concomitant changes in Pacific Ocean- mediated interannual variability.
DE: 3344 Paleoclimatology
DE: 1620 Climate dynamics (3309)
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting