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A millennial summer temperature reconstruction for northeastern Canada using oxygen isotopes in subfossil trees.

Naulier, Maude; Savard, Martine M.; Bégin, Christian; Gennaretti, Fabio; Marion, Joëlle; Nicault, Antoine; Bégin, Yves (2015). A millennial summer temperature reconstruction for northeastern Canada using oxygen isotopes in subfossil trees. Climate of the Past , vol. 11 , nº 9. p. 1153-1164. DOI: 10.5194/cp-11-1153-2015.

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Résumé

Climatic reconstructions for north-eastern Canada are scarce such that this area is under-represented in global temperature reconstructions. To fill this lack of knowledge and identify the most important processes influencing climate variability, this study presents the first summer temperature reconstruction for eastern Canada based on a millennial oxygen isotopic series (δ¹⁸O) from tree rings. For this purpose, we selected 230 well-preserved subfossil stems from the bottom of a boreal lake and five living trees on the lakeshore. The sampling method permitted an annually resolved δ18O series with a replication of five trees per year. The June to August maximal temperature of the last millennium has been reconstructed using the statistical relation between Climatic Research Unit (CRU TS3.1) and δ¹⁸O data. The resulting millennial series is marked by the well-defined Medieval Warm Anomaly (AD 1000–1250), the Little Ice Age (AD 1450–1880) and the modern period (AD 1950–2010), and an overall average cooling trend of −0.6 °C/millennium⁻¹. These climatic periods and climatic low frequency trends are in agreement with the only reconstruction available for northeastern Canada and others from nearby regions (Arctic, Baffin Bay) as well as some remote regions like the Canadian Rockies or Fennoscandia. Our temperature reconstruction clearly indicates that the Medieval Warm Anomaly has been warmer than the modern period, which is relatively cold in the context of the last 1000 years. However, the temperature increase during the last three decades is one of the fastest warming observed over the last millennium (+1.9 °C between 1970 and 2000). An additional key finding of this research is that the coldest episodes mainly coincide with low solar activities and the extremely cold period of the early 19th century has occurred when a solar minimum was in phase with successive intense volcanic eruptions. Our study provides a new perspective unraveling key mechanisms that controlled the past climate shifts in northeastern Canada.

Type de document: Article
Mots-clés libres: climate variation; little Ice Age; oxygen isotope; paleoclimate; paleotemperature; reconstruction; shore (nonmarine); solar activity; subfossil; tree; tree ring; volcanic eruption
Centre: Centre Eau Terre Environnement
Date de dépôt: 23 avr. 2018 15:39
Dernière modification: 23 avr. 2018 15:39
URI: http://espace.inrs.ca/id/eprint/3891

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