This work was supported by the US National Science Foundation (Grants 0956552 and 0966472, to A.H., T.T.V., and J.P.), the Consejo Nacional de Investigaciones Científicas y Técnicas (J.P., I.A.M., and T.K.), the Agencia Nacional de Promoción Científica y Tecnológica (Grants PICT 2012-1891, to I.A.M., and PICT 2012-0949, to J.P.), the Graduate School of the University of Colorado Boulder (A.H. and J.P.), and the Center for Climate and Resilience Research (Comisión Nacional de Investigación Científica y Tecnológica/Fondo de Financiamiento de Centros de Investigación en Áreas Prioritarias/Award 15110009, M.E.G.) and Fondo Nacional de Desarrollo Científico (Grant 1171400, to M.E.G.).
Proceedings of the National Academy of Sciences
Wildfires -- South America -- Effect of climatic changes on, Synchrony, Global warming, Forest fires -- History -- Research, Dendrochronology
The Southern Annular Mode (SAM) is the main driver of climate variability at mid to high latitudes in the Southern Hemisphere, affecting wildfire activity, which in turn pollutes the air and contributes to human health problems and mortality, and potentially provides strong feedback to the climate system through emissions and land cover changes. Here we report the largest Southern Hemisphere network of annually resolved tree ring fire histories, consisting of 1,767 fire-scarred trees from 97 sites (from 22 °S to 54 °S) in southern South America (SAS), to quantify the coupling of SAM and regional wildfire variability using recently created multicentury proxy indices of SAM for the years 1531–2010 AD. We show that at interannual time scales, as well as at multidecadal time scales across 37–54 °S, latitudinal gradient elevated wildfire activity is synchronous with positive phases of the SAM over the years 1665–1995. Positive phases of the SAM are associated primarily with warm conditions in these biomass-rich forests, in which widespread fire activity depends on fuel desiccation. Climate modeling studies indicate that greenhouse gases will force SAM into its positive phase even if stratospheric ozone returns to normal levels, so that climate conditions conducive to widespread fire activity in SAS will continue throughout the 21st century.
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Holz, A., Paritsis, J., Mundo, I. A., Veblen, T. T., Kitzberger, T., Williamson, G. J., ... & Quezada, J. M. (2017). Southern Annular Mode drives multicentury wildfire activity in southern South America. Proceedings of the National Academy of Sciences, 201705168.