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| Titel |
Solar forcing and atmospheric control of paleoflood dynamics in the Bernese Alps, Switzerland |
| VerfasserIn |
Lothar Schulte, Juan Carlos Peña, Francesc Burjachs, Filipe Carvalho, Jaime Llorca, Ramon Julià, Johanna Lomax, Thomas Schmidt, Patricio Rubio, Justino Losada, Heinz Veit |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250089927
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| Publikation (Nr.) |
 EGU/EGU2014-4140.pdf |
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| Zusammenfassung |
| A multidisciplinary approach provides data from natural, historical, and instrumental time
series, for the study of potential effects of climatic changes on alpine floods outside the
known range of extreme events. The research focuses on the densely populated Bernese Alps,
which are a true "hot spot" of hydrological risk. For the reconstruction of climate variability
and floods, interdecadal-resolution alluvial delta plain records were examined. The
multi-proxy approach affords insight into alpine flood dynamics of mid-scale catchments
during the last three millennia.
Spectral analysis of the geochemical and pollen time series records and climate proxies
(δ14C, δ18O isotopes from the Greenland ice, NAO) evidence similar periodicities of 60, 85,
105 and 200 yrs. Thus, the mechanisms of the flood processes are strongly influenced by the
North Atlantic dynamics and solar activity. The proxies indicate that cooler climate pulses
and transitions from cool to warm climate pulses were an important external driving force of
floods. This hypothesis is supported by the reconstructed floods of the Aare and Lütschine
rivers from local documentary sources during the last 500 yrs. Flood periods inferred from
sedimentary archives (flood layers, geochemical proxies and shifts of river channel) were
calibrated by local documentary flood records and compared with the pattern of settlement on
flood prone landforms. The generated data series shows also a good correlation
with climate proxies, such as the annual temperatures of Europe (Luterbacher et
al., 2004), tree ring based summer temperatures of Central Europe (Büntgen et
al., 2011) and total solar irradiance according to the model of Steinhilber et al.
(2009).
With regard to the last two centuries flood magnitude and frequencies (exact dating) as
well as driving mechanisms were reconstructed with more precision. Furthermore, a summer
flood index of Switzerland (INU) based on damages recorded from 1800 to 2008 AD was
performed. Spectral analysis of the INU index identify the 105yr cycle recorded in the delta
plain sediments and the 11-year solar cycle (Schwalbe-cycle). Correlation of the INU with
annual temperature of the Alps region since 1800 AD, the δ18O GISP 2 record and
the summer NAO indicate that mayor flood activity may occurred during short
warm climate pulses (strong positive SNAO) during cold low-frequency periods. |
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