Southern Annular Mode drives multi-century wildfire activity in southern South America

HOLZ, A; PARITSIS, J; MUNDO, I; VEBLEN, TT; KITZBERGER, T; WILLIAMSON, G; ARAOZ, E; BUSTOS, C; GONZALEZ, ME; GRAU, HR; QUEZADA, JM

Chico Springs

Workshop; WildFIRE PIRE Workshop: Understanding climate-human-fire interactions at different temporal and spatial scales; 2017

Montana State University

The Southern Annular Mode (SAM) is the main driver of climate variability at mid-to-highlatitudes in the Southern Hemisphere affecting wildfire activity which in turn pollutes theair and contributes to human health problems and mortality, and potentially has a strongfeedback to the climate system through emissions and land cover change.Here we develop the largest southern hemisphere network of annually-resolved tree-ringfire histories (see Supplementary Table S1) consisting of 1767 fire-scarred trees from 97sites (from 22 to 54o latitude S) to quantify the coupling of SAM and regional wildfirevariability using recently created multi-century proxy indices of SAM for the period 1531to 2010 AD. We show that at interannual time scales as well as at multidecadal time scalesacross the 37 to 54oS latitudinal gradient elevated wildfire activity is synchronous withpositive phases of the SAM over the period from 1665 to 1995 AD. Positive phases of theSAM are primarily associated with warm conditions in these biomass-rich forests in whichwidespread fire activity depends on fuel desiccation. Climate modeling studies indicate thatgreenhouse gasses will force SAM into its positive phase even if stratospheric ozonereturns to normal levels, so that climate conditions conducive to widespread fire activity insouthern South America (SSA) will continue throughout the 21st century.