Informing sedimentary charcoal-based fire reconstructions with a kinematic transport model

Abstract

Recent changes in global fire activity and future projections can be attributed to a combination of direct human impacts and indirect effects of anthropogenic climate change. To understand how and why these shifts might occur, we need to understand the pre-human history of fires during past climatic changes. This is commonly looked at through charcoal preserved in lake sediment records. These paleorecords assume that a certain charcoal particle size class was derived from proximal fires. There are few tests, however, to assess how far charcoal particles can travel from the original fire source. This kinematic model shows that charcoal particle distribution and deposition is strongly influenced not only by the energy release rate and subsequent plume height, but also by the particle size, density, and shape. Each of these factors contributes to a more extensive and incongruous distribution of charcoal particles than previously thought. This model indicates that shape irregularities may cause substantial heterogeneity in the particle-size distribution of charcoal dispersal. In contrast, most studies and models assume particle size varies proportionally with dispersal range. This heterogeneity of charcoal particle dispersal has important implications for charcoal source area and the interpretation of sedimentary charcoal records.