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

• Published in: The Cryosphere
• Main Authors: D. Osmont, S. Brugger, A. Gilgen, H. Weber, M. Sigl, R. L. Modini, C. Schwörer, W. Tinner, S. Wunderle, M. Schwikowski
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2020
• Subjects: envir; geo; Finn; ice core; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-14-3731-2020; https://tc.copernicus.org/articles/14/3731/2020/tc-14-3731-2020.pdf; https://doaj.org/article/2d6c9df77973437ca870ef95bee0efb7

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 ...