Multi-century fire synchrony across western North America: Contingent Effects of ENSO, PDO, and AMO.

SWETNAM, T.W.; KITZBERGER, T.; BROWN, P.M.; HEYERDAHL, E.K.; VEBLEN, T.T.

Bozeman, EEUU

Congreso; XIX AMQUA Biennial Meeting; 2006

The American Quaternary Association

Widespread wildfires are driven by weather and climatic variations across western North America during particular years, such as in 2000 and 2002. These continental-scale events result in major environmental impacts, and costs of suppressing these fires and the losses in resources are valued in the billions of dollars. Numerous tree-ring studies conducted at local scales (10s to 1000s of hectares) have made progress in evaluating paleo-fire and climatic relationships and linkages to broad-scale anomalies in ocean-atmosphere conditions in the north and tropical Pacific and in the north Atlantic (e.g., Swetnam and Betancourt 1990, Veblen et al. 2000, Kitzberger et al. 2001; Heyerdahl et al. 2003) Improved understanding of regional and continental scale patterns of drought related to certain phases of El Niño-Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), and the Atlantic Multidecadal Oscillation (AMO) provides the opportunity to examine climatic relationships of paleo-fire at regional and sub-continental scales (Westerling and Swetnam 2003; Sibold and Veblen 2006; Brown 2006). Based on 33,792 annually resolved fire-scar dates collected at 241 sites across western North America (the largest tree-ring record of fire ever assembled) we reconstruct multi-century climate forcing of forest fires at regional and sub-continental scales over the past c. 500 years. Here, we show that since 1550, drought and forest fires co-varied across western North America, but in a manner contingent on the states of ocean-atmosphere processes. Certain phases of ENSO and the PDO are associated with fire occurrence that is synchronous within regions, and sometimes asynchronous among them (Figure 1). In contrast, fires are synchronous (i.e. positively correlated annually) across the West during warm phases of the Atlantic Multidecadal Oscillation (AMO) (Figure 2). The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. fires are synchronous (i.e. positively correlated annually) across the West during warm phases of the Atlantic Multidecadal Oscillation (AMO) (Figure 2). The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. fires are synchronous (i.e. positively correlated annually) across the West during warm phases of the Atlantic Multidecadal Oscillation (AMO) (Figure 2). The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. fires are synchronous (i.e. positively correlated annually) across the West during warm phases of the Atlantic Multidecadal Oscillation (AMO) (Figure 2). The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. fires are synchronous (i.e. positively correlated annually) across the West during warm phases of the Atlantic Multidecadal Oscillation (AMO) (Figure 2). The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. Figure 1). In contrast, fires are synchronous (i.e. positively correlated annually) across the West during warm phases of the Atlantic Multidecadal Oscillation (AMO) (Figure 2). The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades. Figure 2). The current state of the AMO suggests that we can expect an increase in widespread fires across the western US in coming decades.