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| Titel |
Testing long-term summer temperature reconstruction based on maximum density chronologies obtained by reanalysis of tree-ring data sets from northernmost Sweden and Finland |
| VerfasserIn |
V. V. Matskovsky, S. Helama |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 10, no. 4 ; Nr. 10, no. 4 (2014-08-05), S.1473-1487 |
| Datensatznummer |
250117023
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| Publikation (Nr.) |
 copernicus.org/cp-10-1473-2014.pdf |
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| Zusammenfassung |
| Here we analyse the maximum latewood density (MXD) chronologies of two
published tree-ring data sets: one from Torneträsk region in northernmost
Sweden (TORN; Melvin et al., 2013) and one from northern Fennoscandia (FENN;
Esper et al., 2012). We paid particular attention to the MXD low-frequency
variations to reconstruct summer (June–August, JJA) long-term temperature
history. We used published methods of tree-ring standardization: regional
curve standardization (RCS) combined with signal-free implementation.
Comparisons with RCS chronologies produced using single and multiple
(non-climatic) ageing curves (to be removed from the initial MXD series)
were also carried out. We develop a novel method of standardization, the
correction implementation of signal-free standardization, tailored for
detection of pure low-frequency signal in tree-ring chronologies. In this
method, the error in RCS chronology with signal-free implementation is
analytically assessed and extracted to produce an advanced chronology. The
importance of correction becomes obvious at lower frequencies as smoothed
chronologies become progressively more correlative with correction
implementation. Subsampling the FENN data to mimic the lower chronology
sample size of TORN data shows that the chronologies bifurcate during the
7th, 9th, 17th and 20th centuries. We used the two MXD data sets to
reconstruct summer temperature variations over the period 8 BC through AD
2010. Our new reconstruction shows multi-decadal to multi-centennial
variability with changes in the amplitude of the summer temperature of 2.2 °C on average during the Common Era. Although the MXD data provide palaeoclimate research with a highly reliable summer temperature proxy, the
bifurcating dendroclimatic signals identified in the two data sets imply that future research should aim at a more advanced understanding of MXD
data on distinct issues: (1) influence of past population density
variations on MXD production, (2) potential biases when calibrating
differently produced MXD data to produce one proxy record, (3) influence of
the biological age of MXD data when introducing young trees into the chronology
over the most recent past and (4) possible role of waterlogging in MXD
production when analysing tree-ring data of riparian trees. |
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