CE01 - Terre fluide et solide

Reconstructing regional BuRnt Areas from microcharcoal preserved In marine SEdiments – BRAISE

How charcoal in marine sediments informs past fire regimes

Fire models must be tested against not only with modern observations, but also with observations from past climate conditions to ensure accuracy and to have credibility. Marine charcoal records can provide such information. Yet they describe only the response in the relative level of fire. BRAISE intends to calibrate charcoal in marine sediments in order to provide robust fire metrics and to benchmark quantitative models.

BRAISE intends to calibrate charcoal in marine sediments in order to provide robust fire metrics and to benchmark quantitative models

BRAISE has four objectives: (a) create the first dataset of charcoal accumulation in marine sediments of modern ages; (b) identify spatial patterns in the distribution of charcoal accumulation in a given area, construct hypotheses about its processes and determine local and/or regional scale correction factors affecting this distribution; (c) develop statistical models linking charcoal accumulation to fire regime metrics; (d) explore the model’s predictive performance over the past centuries by comparing predicted theoretical charcoal accumulation with observations from historical reconstructed fires and charcoal accumulation time series obtained during the project. <br />With our new data and tools, BRAISE will address the following research questions: (1) What are the most important processes determining charcoal accumulation in marine sediments? (2) How does charcoal accumulation relate to fire regime metrics? (3) What are the uncertainties and limitations associated with the spatio-temporal distribution of charcoal accumulation in marine sediments?

The BRAISE project focuses on marine sediments within 500 kms from the coastline on a North-South transect from the eastern Atlantic Ocean (northern Europe to southern Africa including the Mediterranean eco-region). This transect had been specifically selected because it provides good sampling of modern climate and vegetation space (from tundra to desert). It also provides a gradient in the level of fire, as some regions today are characterized by high levels of fire and others by lower levels. Thus, it should provide a reasonable basis for reconstructing broad-scale relationships between CHAR in marine realm and fire regimes on the continent. BRAISE method is based on the collection of charcoal data and metadata on marine surface samples and the creation of the BRAISE dataset; the compilation of continent-ocean Geographic Information System (GIS) and fire regime data from satellite observations; exploratory analyses of quantitative relationships between charcoal accumulation and fire regime metrics; and the production of two new charcoal records covering the Holocene on which the calibration can be applied in the future.

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Large uncertainties remain in understanding the evolution of fire activity under projected warming scenarios because fire is a complex process to integrate into global modelling. Empirical models used for projections lack potential changes in the interaction between climate, vegetation and fire. Process-based models of the coupled vegetation-fire system provide new tools to address this issue. Evaluating those models against benchmark datasets from charcoal sediment records, outside of the modern climate conditions range, is necessary. Long marine charcoal records capture regional-scale biomass burning over a large range of natural climate variability, i.e. multiple warm and cold climate states. The development of comprehensive data-model comparisons is limited by the lack of common units between data and model output. BRAISE intends to develop a calibration which, applied on paleofire records, should provide new datasets of regional burnt areas for key periods in the past.

Project coordinator

Madame Anne-Laure Daniau (Environnements et paléoenvironnements océaniques et continentaux)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

EPOC Environnements et paléoenvironnements océaniques et continentaux

Help of the ANR 162,594 euros
Beginning and duration of the scientific project: January 2020 - 48 Months

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