Abstract
Abstract. In this study, vanillic acid was measured in the Tunu ice core from northeastern Greenland in samples covering the past 1700 years. Vanillic acid is an aerosol-borne aromatic methoxy acid, produced by the combustion of lignin during biomass burning. Air mass trajectory analysis indicates that North American boreal forests are likely the major source region for biomass burning aerosols deposited to the ice core site. Vanillic acid levels in the Tunu ice core range from < 0.005 to 0.08 ppb. Tunu vanillic acid exhibits centennial-scale variability in pre-industrial ice, with elevated levels during the warm climates of the Roman Warm Period and Medieval Climate Anomaly, and lower levels during the cooler climates of the Late Antique Little Ice Age and the Little Ice Age. Analysis using a peak detection method revealed a positive correlation between vanillic acid in the Tunu ice core and both ammonium and black carbon in the North Greenland Eemian Ice Drilling (NEEM) project ice core from 600 to 1200 CE. The data provide multiproxy evidence of centennial-scale variability in North American high-latitude fire during this time period.
Highlights
Proxy records of biomass burning are important for understanding the relationship between climate variability and fire on long timescales
Tunu vanillic acid (VA) levels do not exhibit a significant linear trend over the past 1700 years. They do exhibit pronounced variability on centennial timescales (Fig. 2). This variability is observable in the raw data as multidecadal to century-long periods in which all of the measurements were above the detection limit
The variability is more clearly shown in the 40-year bin averages of the log-transformed data (Fig. 3)
Summary
Proxy records of biomass burning are important for understanding the relationship between climate variability and fire on long timescales. A diverse range of paleo-proxies has been used to reconstruct biomass burning, including fire scars on tree rings, sedimentary charcoal records, and ice core records of gases and aerosol-borne chemicals (Blarquez et al, 2014; Legrand et al, 2016; Marlon et al, 2008, 2016; Power et al, 2008, 2013; Rubino et al, 2015). These records reflect a wide range of different aspects of fire location, frequency, distribution, and intensity. Black carbon, and levoglucosan provide evidence for elevated North American burning prior to 500 CE and from 1000 to 1200 CE, these records are not entirely consistent with each other (Chýlek et al, 1995; Legrand et al, 1992, 2016; McConnell et al, 2007; Rubino et al, 2015; Zennaro et al, 2014)
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