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

2015 ◽  
Vol 11 (9) ◽  
pp. 1153-1164 ◽  
Author(s):  
M. Naulier ◽  
M. M. Savard ◽  
C. Bégin ◽  
F. Gennaretti ◽  
D. Arseneault ◽  
...  
Keyword(s):  
Volcanic Eruptions ◽  
Temperature Reconstruction ◽  
Summer Temperature ◽  
Climatic Research Unit ◽  
Last Millennium ◽  
Medieval Climate Anomaly ◽  
Climate Anomaly ◽  
Early 19Th Century ◽  
Modern Period ◽  
Summer Temperature Reconstruction

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.

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

2015 ◽  
Vol 11 (1) ◽  
pp. 521-553 ◽  
Author(s):  
M. Naulier ◽  
M. M. Savard ◽  
C. Bégin ◽  
F. Gennaretti ◽  
D. Arseneault ◽  
...  
Keyword(s):  
Volcanic Eruptions ◽  
Temperature Reconstruction ◽  
Summer Temperature ◽  
Climatic Research Unit ◽  
Last Millennium ◽  
Eastern Canada ◽  
Early 19Th Century ◽  
Modern Period ◽  
Warm Anomaly ◽  
Summer Temperature Reconstruction

Abstract. 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. 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.

Vegetation shifts, human impact and peat bog development in Bassa Nera pond (Central Pyrenees) during the last millennium

The Holocene ◽  
2016 ◽  
Vol 27 (4) ◽  
pp. 553-565 ◽  
Author(s):  
Sandra Garcés-Pastor ◽  
Núria Cañellas-Boltà ◽  
Albert Clavaguera ◽  
Miguel Angel Calero ◽  
Teresa Vegas-Vilarrúbia
Keyword(s):  
Environmental Changes ◽  
Ice Age ◽  
Peat Bog ◽  
High Mountain ◽  
Last Millennium ◽  
Medieval Climate Anomaly ◽  
Human Pressure ◽  
Climate Anomaly ◽  
Vegetation Shifts ◽  
Central Pyrenees

High-mountain lakes are suitable ecosystems for studying local environmental shifts driven by large-scale climate changes, with potential applications to predict future scenarios. The precise features in the response of species assemblages are not fully understood, and human pressure may often hide climatic signals. To investigate the origin and impact of past environmental changes in high-mountain ecosystems and apply this palaeoecological knowledge to anticipate future changes, we performed a multi-proxy study of a sediment core from Bassa Nera, a pond located close to montane–subalpine ecotone in the southern central Pyrenees. Combining pollen and diatom analysis at multidecadal resolution, we inferred vegetation shifts and peat bog development during the past millennium. We introduced a montane pollen ratio as a new palaeoecological indicator of altitudinal shifts in vegetation. Our results emphasize the sensitivity of the montane ratio to detect upward migrations of deciduous forest and the presence of the montane belt close to Bassa Nera pond during the Medieval Climate Anomaly. Changes in aquatic taxa allowed to date the onset of the surrounding peat bog which appeared and infilled the coring site around AD 1565. Overall, our results suggest a low-intensity human pressure and changes in management of natural resources during the last millennium, where farming was the main activity from the Medieval Climate Anomaly until AD 1500. Afterwards, people turned to highland livestock raising coinciding with the ‘Little Ice Age’.

A first chironomid-based summer temperature reconstruction (13–5 ka BP) around 49°N in inland Europe compared with local lake development

2016 ◽  
Vol 141 ◽  
pp. 94-111 ◽  
Author(s):  
Petra Hájková ◽  
Petr Pařil ◽  
Libor Petr ◽  
Barbora Chattová ◽  
Tomáš Matys Grygar ◽  
...  
Keyword(s):  
Temperature Reconstruction ◽  
Summer Temperature ◽  
Lake Development ◽  
Summer Temperature Reconstruction

scholarly journals A Tree-Ring Based Late Summer Temperature Reconstruction (AD 1675–1980) for the Northeastern Mediterranean

Radiocarbon ◽  
2014 ◽  
Vol 56 (4) ◽  
pp. S69-S78 ◽  
Author(s):  
Valerie Trouet
Keyword(s):  
Tree Ring ◽  
Late Summer ◽  
Temperature Reconstruction ◽  
High Elevation ◽  
Global Scale ◽  
Summer Temperature ◽  
Latewood Density ◽  
Reconstructed Temperature ◽  
Tree Ring Data ◽  
Summer Temperature Reconstruction

This article presents a late summer temperature reconstruction (AD 1675–1980) for the northeastern Mediterranean (NEMED) that is based on a compilation of maximum latewood density tree-ring data from 21 high-elevation sites. This study applied a novel approach by combining individual series from all sites into one NEMED master chronology. This approach retains only the series with a strong and temporally robust common signal and it improves reconstruction length. It further improved the regional character of the reconstruction by using as a target averaged gridded instrumental temperature data from a broad NEMED region (38–45°N, 15–25°E). Cold (e.g. 1740) and warm (e.g. 1945) extreme years and decades in the reconstruction correspond to regional instrumental and reconstructed temperature records. Some extreme periods (e.g. cold 1810s) reflect European-wide or global-scale climate conditions and can be explained by volcanic and solar forcing. Other extremes are strictly regional in scope. For example, 1976 was the coldest NEMED summer over the last 350 years, but was anomalously dry and hot in northwestern Europe and is a strong manifestation of the summer North Atlantic Oscillation (sNAO). The regional NEMED summer reconstruction thus contributes to an improved understanding of regional (e.g. sNAO) vs. global-scale (i.e. external) drivers of past climate variability.

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