Playing with fire: Ice core biomass burning records from four continents

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• Dr. Natalie Kehrwald, University of Venice, Italy
• Tuesday 02 July 2013, 11:00-12:00
• room 307, British Antarctic Survey, High Cross, Cambridge, CB3 0ET.

If you have a question about this talk, please contact Dr. Ailsa Benton.

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Aerosols continue to be one of the least understood aspects of the modern climate system and even less is known about their past influence. Ice cores contain specific molecular markers including levoglucosan (1,6-anhydro-β-D-glucopyranose) and other pyrochemical evidence that provides much-needed information on the role of fire aerosols in driving past climate and the possibility of current biomass burning affecting future global climate. In addition to climate and fire linkages, humans have influenced fire activity for thousands of years through changing fire ignition rates, fuels, and land cover. We quantify fire proxy records from four continents to provide an interdisciplinary synthesis of the interactions between past fires, human activity, and climate change. Here, we present levoglucosan flux measured across the past 10,000 years in the EPICA Dome C ice core (7506’S, 12321’E, 3233 masl), Holocene and Eemian levoglucosan concentrations in the NEEM , Greenland (7727’ N; 513’W, 2454 masl) ice core, during the past 4000 years in the Kilimanjaro (304.6’S; 3721.2’E, 5893 masl) ice core, and preliminary Holocene Tibetan Plateau snow pit and ice core results.

Human activities can and have altered fire activity beyond background climate conditions as long ago as the late Pleistocene and have significantly changed vegetation regimes with changing agricultural and pastoral practices. Kilimanjaro levoglucosan concentrations peak 800 – 1000 yr BP, coincident with the largest regional droughts and associated human migration. NEEM Holocene fire activity is highest during decadal-scale northern central Asian droughts and does not demonstrate a modern rise associated with increased settlement in boreal regions. EPICA Dome C results demonstrate an order of magnitude increase in levoglucosan concentrations beginning approximately 500 yr BP that is likely due to human activity rather than changing climate conditions. Unlike methane and its isotopic signatures, levoglucosan is not a globally mixed marker, and these hemispheric differences are consistent with the atmospheric lifetime, sources, and transport of levoglucosan. The EPICA Dome C levoglucosan profile is strikingly similar to regional charcoal compilations from New Zealand and southeastern Australia, and substantially differs from South American records. Transport models demonstrate the possibility of New Zealand and Australia as major levoglucosan sources to EPICA Dome C. These fire histories provide insight into the interplay between climate, human activity, and biomass burning aerosols through time.

This talk is part of the BAS Chemistry & Past Climate Seminars series.

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