A Holocene black carbon ice-core record of biomass burning in the Amazon Basin from Illimani, Bolivia

Abstract

Abstract. The Amazon Basin is one of the major contributors to global\nbiomass burning emissions. However, regional paleofire trends remain\nparticularly unknown. Due to their proximity to the Amazon Basin, Andean ice\ncores are suitable to reconstruct paleofire trends in South America and\nimprove our understanding of the complex linkages between fires, climate and\nhumans. Here we present the first refractory black carbon (rBC) ice-core\nrecord from the Andes as a proxy for biomass burning emissions in the Amazon\nBasin, derived from an ice core drilled at 6300\u2009m\u2009a.s.l. from the Illimani\nglacier in the Bolivian Andes and spanning the entire Holocene back to the\nlast deglaciation 13\u2009000\xa0years ago. The Illimani rBC record displays a\nstrong seasonality with low values during the wet season and high values\nduring the dry season due to the combination of enhanced biomass burning\nemissions in the Amazon Basin and less precipitation at the Illimani site.\nSignificant positive (negative) correlations were found with reanalyzed\ntemperature (precipitation) data for regions in eastern\nBolivia and western Brazil characterized by substantial fire activity. rBC\nlong-term trends indirectly reflect regional climatic variations through\nchanging biomass burning emissions as they show higher (lower) concentrations\nduring warm–dry (cold–wet) periods, in line with climate\nvariations such as the Younger Dryas, the 8.2\u2009ka event, the Holocene\nClimatic Optimum, the Medieval Warm Period and the Little Ice Age. The highest\nrBC concentrations of the entire record occurred during the Holocene Climatic\nOptimum between 7000 and 3000\u2009BCE, suggesting that this exceptionally warm and\ndry period caused high levels of biomass burning activity, unprecedented in the\ncontext of the past 13\u2009000\xa0years. Recent rBC levels, rising since 1730\u2009CE\nin the context of increasing temperatures and deforestation, are similar to\nthose of the Medieval Warm Period. No decrease in fire activity was observed\nin the 20th century, in contradiction to global biomass burning\nreconstructions based on charcoal data.