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| Titel |
The mid- to late-Holocene δD signal of n-alkanoic acids in lake sediments from the Southern Alps |
| VerfasserIn |
Stefanie B. Wirth, Alex L. Sessions, Adrian Gilli |
| 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 |
250094483
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| Publikation (Nr.) |
 EGU/EGU2014-9894.pdf |
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| Zusammenfassung |
| The hydrogen isotopic composition δD of plant leaf waxes has been increasingly
applied in paleoclimate studies over the recent years. Yet, Holocene data from the
mid-latitudes still seems relatively sparse, with one limiting factor certainly being
the expected complex climatic forcings of the water isotopic composition at this
latitude.
In this context, we present a new δD record of n-alkanoic acids from lake sediments in
the Southern Alps (Lake Ghirla, Italy) covering the past 5600 years. The goals of this study
are twofold: i) a general evaluation of the amplitude and quality of the δD signal in the Alpine
region, and ii) identifying the relative importance of different climatic parameters such as
temperature, precipitation, and moisture-source changes on the water isotopic composition of
this region.
First analyses show a variation in δD values of the n-alkanoic acids (C14-28) that spans
25-50 oover the past 5600 years, clearly larger than typical analytical uncertainties. In
addition, the observed pattern is remarkably coherent across all chain lengths, even if the
absolute variation in shorter chain acids (C14-20) is higher than in the longer chain acids
(C22-28). This coherence supports the assumption that the record primarily reflects the
isotopic composition of regional precipitation. Regarding the temporal evolution of the δD
values, we observe two long-term features: a period of only moderate δD variation (C24-28
within 10-15 o) from 5.6-3 cal kyr BP, and a gradual decrease in isotopic composition
(-15-25 o) from ~2 cal kyr BP to the onset of the Little Ice Age. In addition, distinct
excursions towards lighter (-8-15 o) and heavier (+15-30 o) δD values occur at 2.8-2.3
cal kyr BP and during the Little Ice Age, respectively. Since both periods have
been attributed to wetter and cooler climate conditions, this inverse signal seems to
underscore the complex climatic forcing of the water-isotopic composition in this
region.
In order to better understand this δD record, further work will require close
comparison with additional proxy data from the same sediment record as well as
with independent reconstructions of climate and vegetation from the Alps and the
Mediterranean area. With this in hand past changes in the water cycle could be better
constrained. |
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