DOI: 10.25921/fr8s-g616
title: NOAA/WDS Paleoclimatology - Fennoscandia, 500-2004 AD, maximum latewood density, Swedish Scots pine, PAGES Euro-Med 2k Version

description: This paper presents updated tree-ring width (TRW) and maximum density (MXD) from Torneträsk in northern Sweden, now covering the period AD 500-2004. By including data from relatively young trees for the most recent period, a previously noted decline in recent MXD is eliminated. Non-climatological growth trends in the data are removed using Regional Curve Standardization (RCS), thus producing TRW and MXD chronologies with preserved low-frequency variability. The chronologies are calibrated using local and regional instrumental climate records. A boot-strapped response function analysis using regional climate data shows that tree growth is forced by April-August temperatures and that the regression weights for MXD are much stronger than for TRW. The robustness of the reconstruction equation is verified by independent temperature data and shows that 63-64% of the instrumental inter-annual variation is captured by the tree-ring data. This is a significant improvement compared to previously published reconstructions based on tree-ring data from Torneträsk. A divergence phenomenon around AD 1800, expressed as an increase in TRW that is not paralleled by temperature and MXD, is most likely an effect of major changes in the density of the pine population at this northern tree-line site. The bias introduced by this TRW phenomenon is assessed by producing a summer temperature reconstruction based on MXD exclusively. The new data show generally higher temperature estimates than previous reconstructions based on Torneträsk tree-ring data. The late-twentieth century, however, is not exceptionally warm in the new record: On decadal-to-centennial timescales, periods around AD 750, 1000, 1400, and 1750 were equally warm, or warmer. The 200-year long warm period centered on AD 1000 was significantly warmer than the late-twentieth century (p < 0.05) and is supported by other local and regional paleoclimate data. The new tree-ring evidence from Torneträsk suggests that this "Medieval Warm Period" in northern Fennoscandia was much warmer than previously recognized.
description:   MXD data from Torneträsk were first published by Schweingruber et al. (1988). This original data set of 65 individual tree-series covered the time period AD 441-1980
       and is hereafter denoted SEAL80 [WSL (Dendro Database, WSL, Switzerland. http://www.wsl.ch/dendro/dendrodb.html).  
       Here, the MXD data is updated to AD 2004 using new samples from 35 relatively young trees. Thus, the new Torneträsk MXD data-base includes samples from a total
       of 100 trees and covers the period AD 441–2004. Dry dead wood covers the period AD 441–1789 and living trees cover the period AD 1336–2004. No subfossil lake material is
       included in the MXD data. In SEAL80, data for the most recent period originated entirely from old-aged trees and, as a result, tree rings from the twentieth century had a
       much higher average cambial age than the earlier part of the record. The new data have significantly reduced the average cambial age of the tree-ring data in the twentieth
       century. The TRW data are part of a much larger data set than the one used for MXD (Grudd et al. 2002). The TRW data are updated to AD 2004 using the same 35 trees as for MXD
       and a total of 620 trees is now used to cover the period AD 500-2004. The sources of these data are living trees, dead dry wood and subfossil logs that were recovered from small lakes.