Abstract

Abstract. Climatic reconstructions for northeastern 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 Climate Anomaly (MCA; 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 indicates that the Medieval Climate Anomaly was characterized by a temperature range similar to the one of the modern period in the study region. However, the temperature increase during the last 3 decades is one of the fastest warming observed over the last millennium (+1.9 °C between 1970–2000). 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.

Highlights

  • The recently published work of the Intergovernmental Panel on Climate Change (IPCC AR5, 2013; PAGES 2K consortium, 2013) has shown that northeastern Canada is poorly represented among existing millennial temperature reconstructions in the Northern Hemisphere

  • As the purpose of the reconstruction was to identify contrasted periods and important temperature changes over the last millennium, the choice of the sampling method proposed by Boettger and Friedrich (2009) was relevant because it allows for reconstruction of climatic parameters at an annual resolution with a replication of five trees per year

  • The range of δ18O values of trees is between 19.5 and 22.0 ‰, and the largest δ18O differences among trees within a junction is obtained for JP5 (3.8 ‰; Fig. 3a)

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Summary

Introduction

The recently published work of the Intergovernmental Panel on Climate Change (IPCC AR5, 2013; PAGES 2K consortium, 2013) has shown that northeastern Canada is poorly represented among existing millennial temperature reconstructions in the Northern Hemisphere. For this reason, a better knowledge of regional past climate variations registered in natural archives is needed. Obtaining millennial-long, high-resolution temperature reconstructions from additional proxies in northeastern Canada is important to increase our knowledge of the past climate, and better understand the mechanisms of climate change

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