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Holocene flood frequency across the Central Alps - solar forcing and evidence for variations in North Atlantic atmospheric circulation

Wirth, Stefanie B. and Glur, Lukas and Gilli, Adrian and Anselmetti, Flavio S. (2013) Holocene flood frequency across the Central Alps - solar forcing and evidence for variations in North Atlantic atmospheric circulation. Quaternary Science Reviews, 80 . pp. 112-128. ISSN 0277-3791. https://resolver.caltech.edu/CaltechAUTHORS:20140117-081651653

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Abstract

The frequency of large-scale heavy precipitation events in the European Alps is expected to undergo substantial changes with current climate change. Hence, knowledge about the past natural variability of floods caused by heavy precipitation constitutes important input for climate projections. We present a comprehensive Holocene (10,000 years) reconstruction of the flood frequency in the Central European Alps combining 15 lacustrine sediment records. These records provide an extensive catalog of flood deposits, which were generated by flood-induced underflows delivering terrestrial material to the lake floors. The multi-archive approach allows suppressing local weather patterns, such as thunderstorms, from the obtained climate signal. We reconstructed mainly late spring to fall events since ice cover and precipitation in form of snow in winter at high-altitude study sites do inhibit the generation of flood layers. We found that flood frequency was higher during cool periods, coinciding with lows in solar activity. In addition, flood occurrence shows periodicities that are also observed in reconstructions of solar activity from ^(14)C and ^(10)Be records (2500–3000, 900–1200, as well as of about 710, 500, 350, 208 (Suess cycle), 150, 104 and 87 (Gleissberg cycle) years). As atmospheric mechanism, we propose an expansion/shrinking of the Hadley cell with increasing/decreasing air temperature, causing dry/wet conditions in Central Europe during phases of high/low solar activity. Furthermore, differences between the flood patterns from the Northern Alps and the Southern Alps indicate changes in North Atlantic circulation. Enhanced flood occurrence in the South compared to the North suggests a pronounced southward position of the Westerlies and/or blocking over the northern North Atlantic, hence resembling a negative NAO state (most distinct from 4.2 to 2.4 kyr BP and during the Little Ice Age). South-Alpine flood activity therefore provides a qualitative record of variations in a paleo-NAO pattern during the Holocene. Additionally, increased South Alpine flood activity contrasts to low precipitation in tropical Central America (Cariaco Basin) on the Holocene and centennial time scale. This observation is consistent with a Holocene southward migration of the Atlantic circulation system, and hence of the ITCZ, driven by decreasing summer insolation in the Northern hemisphere, as well as with shorter-term fluctuations probably driven by solar activity.


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http://www.sciencedirect.com/science/article/pii/S0277379113003387PublisherArticle
http://dx.doi.org/10.1016/j.quascirev.2013.09.002DOIArticle
Additional Information:© 2013 Elsevier Ltd. Received 20 January 2013. Received in revised form 4 July 2013. Accepted 5 September 2013. Available online 3 October 2013. We thank the numerous people that helped in the field retrieving the sediment cores. We are also grateful to Marian Fujak for measuring 137Cs activities and to the Institute of Diagnostic and Interventional Radiology at the University Hospital Zurich, especially Thomas Frauenfelder and Andrea Marty, for giving us the possibility to do CT scans of the sediment cores. We also thank Christoph Schär for providing us with the necessary background on atmospheric processes, Fabien Arnaud for input on an earlier version of the manuscript, Boris Vannière and Michel Magny for collaboration on Lake Ledro, as well as the two reviewers for their valuable comments and input. This project (‘FloodAlp! Frequency and intensity of extreme floods in the Alps through the Holocene and implications for natural hazards in future climate scenarios’) is funded by the Swiss National Science Foundation (SNF) (Grant 200021-121909).
Funders:
Funding AgencyGrant Number
Swiss National Science Foundation (SNF)200021-121909
Subject Keywords: Alps; Lake sediments; Heavy precipitation; Flood reconstruction; Solar forcing; NAO; North Atlantic
Record Number:CaltechAUTHORS:20140117-081651653
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20140117-081651653
Official Citation:Stefanie B. Wirth, Lukas Glur, Adrian Gilli, Flavio S. Anselmetti, Holocene flood frequency across the Central Alps – solar forcing and evidence for variations in North Atlantic atmospheric circulation, Quaternary Science Reviews, Volume 80, 15 November 2013, Pages 112-128, ISSN 0277-3791, http://dx.doi.org/10.1016/j.quascirev.2013.09.002. (http://www.sciencedirect.com/science/article/pii/S0277379113003387)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43419
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:17 Jan 2014 16:55
Last Modified:03 Oct 2019 06:07

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