Tracing devastating fires in Portugal to a snow archive in the Swiss Alps: a case study

Osmont, Dimitri; Brügger, Sandra; Gilgen, Anina; Weber, Helga; Sigl, Michael; Modini, Robin L.; Schwörer, Christoph; Tinner, Willy; Wunderle, Stefan; Schwikowski, Margit (2020). Tracing devastating fires in Portugal to a snow archive in the Swiss Alps: a case study. The Cryosphere, 14(11), pp. 3731-3745. Copernicus Publications 10.5194/tc-14-3731-2020

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Recent large wildfires, such as those in Portugal in 2017, have devastating impacts on societies, economy, ecosystems and environments. However, wildfires are a natural phenomenon, which has been exacerbated by land use during the past millennia. Ice cores are one of the archives preserving information on fire occurrences over these timescales. A difficulty is that emission sensitivity of ice cores is often unknown, which constitutes a source of uncertainty in the interpretation of such archives. Information from specific and well-documented case studies is therefore useful to better understand the spatial representation of ice-core burning records. The wildfires near Pedrógão Grande in central Portugal in 2017 provided a test bed to link a fire event to its footprint left in a high-alpine snowpack considered a surrogate for high-alpine ice-core sites. Here, we (1) analysed black carbon (BC) and microscopic charcoal particles deposited in the snowpack close to the high-alpine research station Jungfraujoch in the Swiss Alps; (2) calculated backward trajectories based on ERA-Interim reanalysis data and simulated the transport of these carbonaceous particles using a global aerosol-climate model; and (3) analysed the fire spread, its spatial and temporal extent, and its intensity with remote-sensing (e.g. MODIS) Active Fire and Burned Area products. According to modelled emissions of the FINN v1.6 database, the fire emitted a total amount of 203.5 t BC from a total burned area of 501 km2 as observed on the basis of satellite fire products. Backward trajectories unambiguously linked a peak of atmospheric-equivalent BC observed at the Jungfraujoch research station on 22 June – with elevated levels until 25 June – with the highly intensive fires in Portugal. The atmospheric signal is in correspondence with an outstanding peak in microscopic charcoal observed in the snow layer, depositing nearly as many charcoal particles as during an average year in other ice archives. In contrast to charcoal, the amount of atmospheric BC deposited during the fire episode was minor due to a lack of precipitation. Simulations with a global aerosol-climate model suggest that the observed microscopic charcoal particles originated from the fires in Portugal and that their contribution to the BC signal in snow was negligible. Our study revealed that microscopic charcoal can be transported over long distances (1500 km) and that snow and ice archives are much more sensitive to distant events than sedimentary archives, for which the signal is dominated by local fires. The findings are important for future ice-core studies as they document that, for BC as a fire tracer, the signal preservation depends on precipitation. Single events, like this example, might not be preserved due to unfavourable meteorological conditions.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Department of Biology > Institute of Plant Sciences (IPS)
08 Faculty of Science > Institute of Geography > Physical Geography > Unit Remote Sensing
08 Faculty of Science > Physics Institute > Climate and Environmental Physics
10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)
08 Faculty of Science > Department of Chemistry, Biochemistry and Pharmaceutical Sciences (DCBP)
08 Faculty of Science > Institute of Geography
08 Faculty of Science > Institute of Geography > Physical Geography
08 Faculty of Science > Department of Biology > Institute of Plant Sciences (IPS) > Palaeoecology

UniBE Contributor:

Brügger, Sandra Olivia; Weber, Helga; Sigl, Michael; Schwörer, Christoph; Tinner, Willy; Wunderle, Stefan and Schwikowski, Margit

Subjects:

500 Science > 580 Plants (Botany)
500 Science > 530 Physics
500 Science > 540 Chemistry
500 Science > 570 Life sciences; biology
900 History > 910 Geography & travel

ISSN:

1994-0416

Publisher:

Copernicus Publications

Language:

English

Submitter:

Nils Rietze

Date Deposited:

02 Sep 2020 08:14

Last Modified:

22 Jun 2021 08:17

Publisher DOI:

10.5194/tc-14-3731-2020

BORIS DOI:

10.7892/boris.146088

URI:

https://boris.unibe.ch/id/eprint/146088

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