Wildfire activity in rainforests in western Patagonia linked to the Southern Annular Mode

Increased wildfire activity in relation to future climate warming is likely for temperate rainforest biomes where fire depends on anomalously dry fuel conditions. Tree-ring fire history records were developed from fires scars in western Patagonia, and synchrony in fire activity was examined to determine the role of regional climate variability in promoting fires. Interannual variability in the multicentury fire history records was related to El Nino-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) and the Southern Annular Mode (SAM). Interannual fire synchrony and decadal-scale trends in wildfires document a strong influence of broad-scale climatic variability on wildfires in western Patagonia. SAMis above average during years of regional drought that coincide with widespread fires. Analyses of contingent interactions of ENSO, PDO and SAM revealed that fire frequencies were greater than expected only when SAM was in its positive phase, regardless of the phase of ENSO and PDO. The fire-enhancing influence of SAM was greatest when PDO was also positive, which indicates Pacific-wide warmer conditions. There is a strong increase in wildfire activity coincident with warming and drying trends during the 20th century and with variability in SAM, which is predicted to continue to be in this fire-conducive phase for the 21st century.