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TitreTemporal instability of isotopes-climate statistical relationships - A study of black spruce trees in northeastern Canada
AuteurNaulier, M; Savard, M M; Bégin, C; Marion, J; Nicault, A; Bégin, Y
SourceEarth and Planetary Science Letters vol. 34, 2015 p. 33-42, https://doi.org/10.1016/j.dendro.2015.04.001
Année2015
Séries alt.Secteur des sciences de la Terre, Contribution externe 20140143
ÉditeurElsevier
Documentpublication en série
Lang.anglais
DOIhttps://doi.org/10.1016/j.dendro.2015.04.001
Mediapapier; en ligne; numérique
Formatspdf
ProvinceQuébec
SNRC23E
Lat/Long OENS-72.0000 -70.0000 54.0000 53.0000
Sujetsisotopes; études des isotopes stables; végétation; isotopes de carbone; isotopes d'oxygène; dendrochronologie; climat; climatologie; fluctuations climatiques; géochronologie
Illustrationslocation maps; plots; histrograms; tables
ProgrammeDéveloppement durable des sables bitumineux, Géosciences de l'environnement
Résumé(disponible en anglais seulement)
Climate reconstructions using stable isotopes (d18O and d13C values) in tree rings are based on relationships of the present climatic conditions with isotopic series. This widely used approach relies on the assumption that correlations between stable isotopes and climatic conditions are steady over time. In this paper, we evaluate the strength of the correlations between d18O and d13C series with several climatic parameters on fourteen black spruce trees coming from three different sites, in northeastern Canada. We applied a 21-year moving window on the r Pearson calculated between stable isotopes and March-May and June-August precipitation, June-August and April-June maximal temperatures. Our results indicate that despite the large distance and differences in stand conditions between the sites, the three sites responded in the same way over time. We show that the isotope-climate relationships changed over time and that the correlations varied with the type of isotopic values and with the climatic parameters used. We also suggest that the climatic ambiance has changed during the 1980-1990 period, as caused by a positive north Atlantic oscillation index. Consequently, d13C values are not controlled anymore by spring precipitation or summer maximal temperature in the following two decades. As opposed to d13C series, the relationship between summer maximal temperature and d18O values was stable over time, and decreased only in the last decade. All these results attest of a ¿divergence problem¿ in the last decades which is most pronounced for d13C series. To explain the divergence between d13C series and spring precipitation during the 1985-1995 period, we show that a strong and positive winter NAO has led to colder and drier winter climatic conditions and consequently, to a decrease of snow cover. We also show that with warmer conditions in spring, summer and fall, an increase of degree-days translated in an extended growing season (beginning sooner and finishing later than before). In these circumstances, the d18O values become increasingly influenced by spring and autumn conditions in the last decade, i.e., by source water with lower d18O values. We conclude that the spruce d18O series appears to be the most appropriate indicator for reconstructing June-August maximal temperature in the studied area despite the divergence issue, given that the calibration-validation tests and reconstruction can exclude the divergent last decade.
Résumé(Résumé en langage clair et simple, non publié)
La reconstitution climatique sur plusieurs siècles à l'aide des isotopes stables de l'oxygène et du carbone de cernes de croissance se base sur les liens statistiques qui existent entre les conditions climatiques et les réponses isotopiques de l'arbre. Cette approche est largement acceptée par la communauté scientifique, mais elle présume d'une stabilité de la relation isotope-climat. Or, notre compilation des données météorologiques mensuelles pour le Nord québécois et nos nouveaux résultats isotopiques montrent: que les conditions climatiques ont changé au cours des dernières décennies pour cause de changement d'ambiance climatique induit par l'homme, et que les relations isotopes-climat en ont été modifiées. Si bien que la reconstitution climatique basée les séries isotopiques de cernes de croissance pour le Nord du Québec devra exclure les dernières décennies de manière à produire des modèles statistiques exprimant une ambiance climatique plus fidèle aux conditions anciennes. Ce travail permet d¿affiner la façon d¿aborder la reconstitution climatique dans la région des grands réservoirs hydroélectriques, pour éventuellement mieux prédire les effets du changement climatique sur la production énergétique au Québec.
GEOSCAN ID295051