5 kyr of fire history in the High North Atlantic Region: natural variability and ancient human forcing

Abstract. Biomass burning influences global atmospheric chemistry by releasing greenhouse gases and climate-forcing aerosols. There is controversy about the magnitude and timing of Holocene changes in biomass burning emissions from millennial to centennial time scales and, in particular, on the possible impact of ancient civilizations. Here we present a 5 kyr record of fire activity proxies levoglucosan, black carbon and ammonium measured in the RECAP ice core, drilled in the coastal East Greenland and therefore affected by processes occurring in the High North Atlantic Region. Levoglucosan and ammonium fluxes show high levels from 5 to 4.5 kyr followed by an abrupt decline, possibly due to monotonic decline in Northern Hemisphere summer insolation. Levoglucosan and black carbon show an abrupt decline at 1.1 kyr BP (before 2000 AD), suggesting a decline in wildfire regime in the Icelandic territory due to the extensive land clearing caused by Viking colonizers. A minimum is reached at 0.5 kyr BP for all fire proxies, after which levoglucosan and ammonium fluxes increase again, in particular over the last 200 years. We find that the fire regime reconstructed from RECAP fluxes seems mainly related to climatic changes, however over the last millennium human activities might have had a substantial influence controlling the occurrence of fire.