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A 7400-year tree-ring chronology in northern Swedish Lapland: Natural climatic variability expressed on annual to millennial timescales
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
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2002 (English)In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 12, no 6, 657-665 p.Article in journal (Refereed) Published
Abstract [en]

Tree-ring widths from 880 living, dry dead, and subfossil northern Swedish pines (Pinus sylvestris L.) have been assembled into a continuous and precisely dated chronology (the Tornetrask chronology) covering the period 5407 BC to AD 1997. Biological trends in the data were removed with autoregressive standardization (ARS) to emphasize year-to-year variability, and with regional curve standardization (RCS) to emphasize variability on timescales from decades to centuries. The strong association with summer mean temperature (June-August) has enabled the production of a temperature reconstruction for the last 7400 years, providing information on natural summer-temperature variability on timescales from years to centuries. Numerous cold episodes, comparable in severity and duration to the severe summers of the seventeenth century, are shown throughout the last seven millennia. Particularly severe conditions suggested between 600 and 1 BC correspond to a known period of glacier expansion, The relatively warm conditions of the late twentieth century do not exceed those reconstructed for several earlier time intervals, although replication is relatively poor and confidence in the reconstructions is correspondingly reduced in the pre-Christian period, particularly around 3000, 1600 and 330 BC. Despite the use of the RCS approach in chronology construction, the 7400-year chronology does not express the full range of millennial-timescale temperature change in northern Sweden.

Place, publisher, year, edition, pages
2002. Vol. 12, no 6, 657-665 p.
Keyword [en]
dendroclimatology; tree rings; climate; summer temperature; Pinus sylvestris; northern Scandinavia; Holocene
National Category
Natural Sciences
URN: urn:nbn:se:su:diva-22689DOI: 10.1191/0959683602hl578rpOAI: diva2:189269
Part of urn:nbn:se:su:diva-1034Available from: 2006-05-08 Created: 2006-05-08 Last updated: 2011-01-25Bibliographically approved
In thesis
1. Tree Rings as Sensitive Proxies of Past Climate Change
Open this publication in new window or tab >>Tree Rings as Sensitive Proxies of Past Climate Change
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the boreal forests of the Northern Hemisphere, time series of tree-ring width (TRW) and maximum density in the latewood (MXD) are highly correlated to local instrumental summer-temperature data and are thus widely used as proxies in high-resolution climate reconstructions. Hence, much of our present knowledge about climatic variability in the last millennium is based on tree-rings. However, many tree-ring records have a lack of data in the most recent decades, which severely hampers our ability to place the recent temperature increase in a longer-timescale perspective of natural variability.

The main objective of this thesis is to update and extend the Torneträsk TRW and MXD records in northern Sweden. Local instrumental climate-data is used to calibrate the new tree-ring records. The results show that TRW is mainly forced by temperature in the early growing season (June/July) while MXD has a wider response window (June – August) and has a higher correlation to temperature. Two reconstructions of summer temperature are made for (i) the last 7,400 years based on TRW, and (ii) the last 1,500 years based on a combination of TRW and MXD. The reconstructions show natural variability on timescales from years to several centuries. The 20th century does not stand out as a notably warm period in the long timescale perspective. A medieval period from AD 900 – 1100 is markedly warmer than the 20th century.

The environmental impact from a large explosive volcanic eruption in 1628/1627 BC is analysed in the tree rings of 14C-dated bog pines in south-central Sweden and in absolutely-dated subfossil pines from Torneträsk. The results show evidence of an impact in the southern site at approximately this time but no detectable impact in the North.

Subfossil trees of Fitzroya cupressoides in southern Chile were 14C-dated to approx. 50,000 years BP and amalgamated into a 1,229-year TRW chronology. This tree-ring record is the oldest in the world. The variability in this Last-glacial chronology is similar to the variability in present-day living trees of the same species. These results suggest that the growth–forcing mechanisms 50,000 years ago were similar to those at present.

Place, publisher, year, edition, pages
Stockholm: Institutionen för naturgeografi och kvartärgeologi, 2006. 75 p.
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 1
Tree ring, width, density, climate, temperature, change, variability, sensitivity, Torneträsk, Tornetrask, Sweden, Fennoscandia, explosive, volcanic, eruption, Santorini, Thera, subfossil, Fitzroya, Chile
National Category
Physical Geography
urn:nbn:se:su:diva-1034 (URN)91-7155-251-0 (ISBN)
Public defence
2006-06-02, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 8 A, Stockholm, 13:00
Available from: 2006-05-08 Created: 2006-05-08Bibliographically approved

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Grudd, Håkan
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