Journal cover Journal topic
Climate of the Past An interactive open-access journal of the European Geosciences Union
Clim. Past, 14, 21-37, 2018
https://doi.org/10.5194/cp-14-21-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
10 Jan 2018
Temperature and mineral dust variability recorded in two low-accumulation Alpine ice cores over the last millennium
Pascal Bohleber1,2,3, Tobias Erhardt4,5, Nicole Spaulding1, Helene Hoffmann2, Hubertus Fischer4,5, and Paul Mayewski1 1Climate Change Institute, University of Maine, Orono, Maine, USA
2Institute of Environmental Physics, Heidelberg University, Heidelberg, Germany
3Institute for Interdisciplinary Mountain Research, Austrian Academy of Sciences, Innsbruck, Austria
4Climate and Environmental Physics, Physics Institute, University of Bern, Bern, Switzerland
5Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
Abstract. Among ice core drilling sites in the European Alps, Colle Gnifetti (CG) is the only non-temperate glacier to offer climate records dating back at least 1000 years. This unique long-term archive is the result of an exceptionally low net accumulation driven by wind erosion and rapid annual layer thinning. However, the full exploitation of the CG time series has been hampered by considerable dating uncertainties and the seasonal summer bias in snow preservation. Using a new core drilled in 2013 we extend annual layer counting, for the first time at CG, over the last 1000 years and add additional constraints to the resulting age scale from radiocarbon dating. Based on this improved age scale, and using a multi-core approach with a neighbouring ice core, we explore the time series of stable water isotopes and the mineral dust proxies Ca2+ and insoluble particles. Also in our latest ice core we face the already known limitation to the quantitative use of the stable isotope variability based on a high and potentially non-stationary isotope/temperature sensitivity at CG. Decadal trends in Ca2+ reveal substantial agreement with instrumental temperature and are explored here as a potential site-specific supplement to the isotope-based temperature reconstruction. The observed coupling between temperature and Ca2+ trends likely results from snow preservation effects and the advection of dust-rich air masses coinciding with warm temperatures. We find that if calibrated against instrumental data, the Ca2+-based temperature reconstruction is in robust agreement with the latest proxy-based summer temperature reconstruction, including a Little Ice Age cold period as well as a medieval climate anomaly. Part of the medieval climate period around AD 1100–1200 clearly stands out through an increased occurrence of dust events, potentially resulting from a relative increase in meridional flow and/or dry conditions over the Mediterranean.

Citation: Bohleber, P., Erhardt, T., Spaulding, N., Hoffmann, H., Fischer, H., and Mayewski, P.: Temperature and mineral dust variability recorded in two low-accumulation Alpine ice cores over the last millennium, Clim. Past, 14, 21-37, https://doi.org/10.5194/cp-14-21-2018, 2018.
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Short summary
The Colle Gnifetti (CG) glacier is the only drilling site in the European Alps offering ice core records back to some 1000 years. We aim to fully exploit these unique long-term records by establishing a reliable long-term age scale and an improved ice core proxy interpretation for reconstructing temperature. Our findings reveal a site-specific temperature-related signal in the trends of the mineral dust proxy Ca2+ that may supplement other proxy evidence over the last millennium.
The Colle Gnifetti (CG) glacier is the only drilling site in the European Alps offering ice core...
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