Abstract
Wildfire can influence climate directly and indirectly, but little is known about the relationships between wildfire and climate during the Quaternary, especially how wildfire patterns varied over glacial-interglacial cycles. Here, we present a high-resolution soot record from the Chinese Loess Plateau; this is a record of large-scale, high-intensity fires over the past 2.6 My. We observed a unique and distinct glacial-interglacial cyclicity of soot over the entire Quaternary Period synchronous with marine δ18O and dust records, which suggests that ice-volume-modulated aridity controlled wildfire occurrences, soot production, and dust fluxes in central Asia. The high-intensity fires were also found to be anticorrelated with global atmospheric CO2 records over the past eight glacial-interglacial cycles, implying a possible connection between the fires, dust, and climate mediated through the iron cycle. The significance of this hypothetical connection remains to be determined, but the relationships revealed in this study hint at the potential importance of wildfire for the global climate system.
Highlights
Wildfire can influence climate directly and indirectly, but little is known about the relationships between wildfire and climate during the Quaternary, especially how wildfire patterns varied over glacial– interglacial cycles
Modern wildfire observations have highlighted influences on atmospheric chemistry caused by the emissions of greenhouse gases—carbon dioxide (CO2), methane (CH4), carbon monoxide (CO), and aerosols—organic carbon (OC) and black carbon (BC) [3, 4]
We propose that the wildfires contributed soluble iron and other substances to the global ocean by direct emission [11, 12] and via atmospheric processes [12, 24, 25], raising the possibility of some involvement in glacial–interglacial climate change
Summary
Wildfire can influence climate directly and indirectly, but little is known about the relationships between wildfire and climate during the Quaternary, especially how wildfire patterns varied over glacial– interglacial cycles. In the past decade an additional effect of wildfire on climate has been recognized; that is, the fires supply soluble, bioavailable iron to the oceans, in addition to other micronutrients such as organic N and P [9, 10], possibly promoting the growth of marine phytoplankton and affecting the concentration of atmospheric CO2 [11, 12]. Charcoal and BC proxies for wildfire reconstruction do not have clear connections to climate Both high and low temperatures, and dry and wet climatic conditions, have been linked to wildfire occurrences [14, 15]. Soot particles, produced via a high-temperature gas-to-particle conversion under dry conditions [18], are predominantly in the Significance
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