Radiocarbon analysis in an Alpine ice core: record of anthropogenic and biogenic contributions to carbonaceous aerosols in the past (1650–1940)
1Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland
2Paul Scherrer Institut, Villigen PSI, Switzerland
3Institute for Particle Physics, ETH Hönggerberg, Zürich, Switzerland
4Paul Scherrer Institut, c/o Institute for Particle Physics, ETH Hönggerberg, Zürich, Switzerland
Abstract. Long-term concentration records of carbonaceous particles (CP) are of increasing interest in climate research due to their not yet completely understood effects on climate. Nevertheless, only poor data on their concentrations and sources in the past is available. We present a first long-term record of organic carbon (OC) and elemental carbon (EC) concentrations - the two main fractions of CP – along with the corresponding fraction of modern carbon (fM) derived from radiocarbon (14C) analysis. The combination of concentration measurements with 14C analysis of CP allows a distinction and quantification of natural, biogenic and anthropogenic fossil sources in the past. CP were extracted from an ice archive, with resulting carbon quantities in the microgram range. Analysis of 14C by accelerator mass spectrometry (AMS) was therefore highly demanding. We analysed 33 samples of 0.4 to 1 kg ice from a 150.5 m long ice core retrieved at Fiescherhorn glacier in December 2002 (46°33'3.2" N, 08°04'0.4'' E; 3900 m a.s.l.). Samples were taken from below the firn/ice transition down to bedrock, covering the time period 1650–1940 and thus the transition from the pre-industrial to the industrial era. Before 1800, OC was of pure biogenic origin with a mean concentration of 21±2 μg kg−1}. In 1940, OC concentration was more than a factor of 3 higher than this biogenic background, almost half of it originating from anthropogenic sources, i.e. from combustion of fossil fuels. The biogenic EC concentration was nearly constant over the examined time period with 6±1 μg kg−1. In 1940, the additional anthropogenic input of atmospheric EC was about 50 μg kg−1.