2–7 Oct 2022
Crans-Montana
Europe/Zurich timezone

Black Carbon and Dust Deposition on South Cascade Glacier, Washington State, USA, Spanning 1840-2014: A Reconstruction of Fossil Fuel and Forest Fire Emissions, and Associated Snow Albedo Impacts

3 Oct 2022, 11:20
20m
Centre de Congrès Le Régent (Crans-Montana)

Centre de Congrès Le Régent

Crans-Montana

Route des Mélèzes 28 3963 Crans-Montana
Oral presentation Pollution records

Speaker

Susan Kaspari (Central Washington University)

Description

Light absorbing particles (LAPs) include black carbon (BC) and mineral dust and are of interest due to their positive radiative forcing and contribution to albedo reductions and snow and glacier melt. This study documents historic BC and dust deposition as well as their effect on albedo on South Cascade Glacier (SCG) in Washington State (USA) through the analysis of a 158-m (139.5-m water equivalent [w.e.]) ice core extracted in 1994 and spanning the period 1840–1991, and three shallow ice cores collected in 2014. Peak BC deposition occurred between 1940 and 1960, when median BC concentrations were 16 times higher than background, likely dominated by domestic coal and forest fire emissions. Post 1960 BC concentrations decrease, followed by an increase from 1977 to 1991 due to melt consolidation and higher emissions. BC concentrations in the 2014 shallow cores remain elevated above background levels, and C14 analysis indicates that ~70% of the 2014 BC is from non-fossil fuels sources. Differences between the SCG record and BC emission inventories, as well as ice core records from other regions, highlight regional differences in the timing of anthropogenic and biomass BC emissions. Dust deposition on SCG is dominated by local sources and is variable throughout the record. Albedo reductions from LAP are dominated by dust deposition, except during high BC deposition events from forest fires and during 1940–1960 when BC and dust similarly contribute to albedo reductions.

Primary authors

Susan Kaspari (Central Washington University) Mr Dan Pittenger (Central Washington University) Theo Manuel Jenk (PSI - Paul Scherrer Institut) Dr Uwe Morgenstern (Institute of Geological and Nuclear Sciences, National Isotope Centre,) Mr Aaron Heslip (Central Washington University) Mr Anthony Perez (Central Washington University) Margit Schwikowski-Gigar (PSI - Paul Scherrer Institut) Dr Chiara Uglietti Dr Matthias Vonwiller Sönke Szidat (University of Bern) Dr Nik Buenning Prof. Lowell Stott (University of Southern California)

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