Abstract
ABSTRACTWe demonstrate the use of levoglucosan (1,6-anhydro-β-d-glucopyranose) as a source-specific proxy of past fire activity in snow pits and ice cores. Levoglucosan is unambiguously a degradation product derived from cellulose burning at temperatures greater than 300 °C and is widely used as a biomass burning marker in aerosol analyses. We analyse samples collected from a 3 m snow pit at Summit, Greenland (72°20′N, 38°45′W; 3270 m a.s.l.), with a known depositional history where biomass burning aerosols were traced from their source in a Canadian smoke plume, through their eastward transport and deposition on the Greenland ice sheet, and their eventual burial by accumulating snow layers. The snow pit levoglucosan profile replicates oxalate concentrations from a known forest fire event, suggesting the applicability of levoglucosan as a marker of past fire activity in snow and by extension in ice cores. However, levoglucosan concentration peaks in the snow pit differ from those of ammonium and potassium, which are traditionally used as biomass burning proxies in snow and ice studies but which incorporate sources other than fire activity. The source specificity of levoglucosan can help determine the past relative contribution of biomass burning aerosols when used in conjunction with other proxies in snow and ice.
Highlights
Biomass burning aerosols are one of the least understood aspects of the modern climate system and even less is known about their past influence (Solomon et al, 2007)
Ice core records and snow pit samples have previously lacked a specific marker for past biomass burning
Indicators such as oxalate, ammonia and potassium ions that have been used as proxies for past fire events in ice cores have more than one source
Summary
Biomass burning aerosols are one of the least understood aspects of the modern climate system and even less is known about their past influence (Solomon et al, 2007). Ice cores and snow pits provide essential information regarding past atmospheric chemistry, and proxies such as ammonium, potassium, oxalate and isotopic ratios in methane (CH4) or carbon monoxide (CO) have been used to estimate previous periods of increased fire activity Many studies focus on establishing episodic biomass burning events as recorded in snow and ice using elevated concentrations of various chemical species, including black carbon and soot (Hansen and Nazarenko, 2004), ammonium (Stohl et al, 2007) and potassium (Echalar et al, 1995). We compare snow pit levoglucosan concentrations with other paleofire chemical indicators and with direct atmospheric measurements of fire emissions As both levoglucosan and climate parameters are measured from the same snow or ice strata, the multiproxy record of snow pits and by extension of ice cores presents an ideal material to investigate the links between fires and climate
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