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| Titel |
A 400 year reconstruction of July relative air humidity for the region Vienna (eastern Austria) based on carbon and oxygen stable isotope ratios in tree-ring latewood cellulose of oaks |
| VerfasserIn |
M. Haupt, T. Boettger, M. Weigl, M. Grabner |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250026616
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| Zusammenfassung |
| Stable isotope chronologies and correlation to climate. We present the stable isotope
chronologies of carbon (δ13Clw) and oxygen (δ18Olw) for the period from 1600 to 2003
respectively of non-exchangeable hydrogen (δ2Hlw) for the last century constructed base
upon tree-ring latewood cellulose from oaks (Quercus petraea Matt. Liebl.) grown in the
region Vienna (Austria). The stable isotope ratios correspond mainly to the summer climate
conditions. For the calibration period (1900-2003) we found high significant correlations
(p < 0.001) between δ13Clw and relative air humidity (RH) of July (-0.66), between δ18Olw
and RHV I-V II (-0.61) and between δ2Hlw and RHV I-V III(-0.56). In the case of
temperatures high significant correlations between the growing season temperature and
δ13Clw (0.55), between the annual mean temperatures and δ18Olw ratios (0.45) and
between summer mean temperatures (June to August) and δ2Hlw values (0.49) were
estimated.
Modeling. Various univariate and multivariate linear regressions models were proved for
the reconstruction of summer relative air humidity and temperature. We found that
establishing of robust models had several uncertainties:
- using common linear transfer functions which oversimplify the complexity of
relations;
- using of pooled material and neglecting of different reactions from individual trees to
climate;
- high-order autocorrelations in the isotope time series;
- climatic trends in the investigated region which are different in the first and in the
second half of 20th century;
- temporal instability of climate signals in the isotope ratios of tree ring cellulose.
In the case of temperature no valid model could be estimated caused by temporal
instabilities of signal strength. For relative air humidity two bivariate models
RHV II = (-4.3 ± 0.7) * δ13Clw + (-2.8 ± 0.5) * δ18Olw + 44 [1]
and
RHV II = (-4.7 ± 0.7) * δ13Clw + (-0.35 ± 0.07) * δ2Hlw - 68 [2]
were found as verifiable and applicable to reconstruct RHV II. Using of δ2Hlw
instead of δ18Olw enhances significantly the model verification. Unfortunately
the data of non-exchangeable hydrogen were available only for the last 100 years.
Therefore the reconstruction of July relative air humidity was carried out only with eq.
[1].
Reconstruction. The predicted RHV II values oscillate in the period from 1600 to 2003
around a mean of 74.7±4.4%. The course of RHV II during this time seems to be periodic
with wetting and drying periods in a cycle of approximately 130 years. Predominant wet
conditions could be reconstructed for the periods 1690-1710, 1765-1820 and 1900-1960,
predominant dry periods for the periods from 1715 to 1730, from 1830 to 1870 and from
approximately 1960 to recent. These results correspond in general with the European Alpine
moisture variability for the period 1800-2003 reported by van der Schrier et al.
(2006).
Extreme wet summer conditions could be reconstructed for 1663, 1795, 1816, 1906, 1915
and 1926. Exceptionally dry summers were supposed for 1616, 1636, 1637, 1751, 1822,
1857, 1863, 1990, 1992 and 2001. These results correspond to instrumental data
and can be well verified by independent reconstructions (Glaser 2001; Casty et al.
2005).
ACKNOWLEDGEMENTS
This work was funded by EC grants EVK2-CT-2002-00147 (ISONET) and 017008
(GOCE; MILLENNIUM).
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