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The Cryosphere An interactive open-access journal of the European Geosciences Union
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Volume 12, issue 10 | Copyright
The Cryosphere, 12, 3311-3331, 2018
https://doi.org/10.5194/tc-12-3311-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 16 Oct 2018

Research article | 16 Oct 2018

19th century glacier retreat in the Alps preceded the emergence of industrial black carbon deposition on high-alpine glaciers

Michael Sigl1,2, Nerilie J. Abram3, Jacopo Gabrieli4, Theo M. Jenk1,2, Dimitri Osmont1,2,5, and Margit Schwikowski1,2,5 Michael Sigl et al.
  • 1Laboratory of Environmental Chemistry, Paul Scherrer Institut, 5232 Villigen, Switzerland
  • 2Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland
  • 3Research School of Earth Sciences and the ARC Centre of Excellence for Climate System Science, Australian National University, Canberra 2601 ACT, Australia
  • 4Institute for the Dynamics of the Environmental Sciences, National Research Council (IDPA-CNR), 30172 Venice, Italy
  • 5Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland

Abstract. Light absorbing aerosols in the atmosphere and cryosphere play an important role in the climate system. Their presence in ambient air and snow changes the radiative properties of these systems, thus contributing to increased atmospheric warming and snowmelt. High spatio-temporal variability of aerosol concentrations and a shortage of long-term observations contribute to large uncertainties in properly assigning the climate effects of aerosols through time.

Starting around AD1860, many glaciers in the European Alps began to retreat from their maximum mid-19th century terminus positions, thereby visualizing the end of the Little Ice Age in Europe. Radiative forcing by increasing deposition of industrial black carbon to snow has been suggested as the main driver of the abrupt glacier retreats in the Alps. The basis for this hypothesis was model simulations using elemental carbon concentrations at low temporal resolution from two ice cores in the Alps.

Here we present sub-annually resolved concentration records of refractory black carbon (rBC; using soot photometry) as well as distinctive tracers for mineral dust, biomass burning and industrial pollution from the Colle Gnifetti ice core in the Alps from AD1741 to 2015. These records allow precise assessment of a potential relation between the timing of observed acceleration of glacier melt in the mid-19th century with an increase of rBC deposition on the glacier caused by the industrialization of Western Europe. Our study reveals that in AD1875, the time when rBC ice-core concentrations started to significantly increase, the majority of Alpine glaciers had already experienced more than 80% of their total 19th century length reduction, casting doubt on a leading role for soot in terminating of the Little Ice Age. Attribution of glacial retreat requires expansion of the spatial network and sampling density of high alpine ice cores to balance potential biasing effects arising from transport, deposition, and snow conservation in individual ice-core records.

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The fast retreat of Alpine glaciers since the mid-19th century documented in photographs is used as a symbol for the human impact on global climate, yet the key driving forces remain elusive. Here we argue that not industrial soot but volcanic eruptions were responsible for an apparently accelerated deglaciation starting in the 1850s. Our findings support a negligible role of human activity in forcing glacier recession at the end of the Little Ice Age, highlighting the role of natural drivers.
The fast retreat of Alpine glaciers since the mid-19th century documented in photographs is used...
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