Arctic Borderlands Ecological Knowledge Co-op
Indicator Assessment: Tree Ring Analysis for Past Climate Change Information
One of the difficulties of following long term changes in climate is the absence of extensive instrument records. Many researchers have been able to use the widths of tree rings as an indicator of past climate. The technique of dendrochronology relies on the observation that trees leave a record of their growth in annual rings; in good years (e.g. warm summers) the ring is relatively wide while in poor weather years the ring is narrower. The sequence of rings can be individually measured and used to generate a unique pattern that can then be tied to other older trees in the area by cross dating. The end result is a composite series of tree rings which may extend many hundred years before present. Actual climate data from recent instrument records can be used to correlate the recent portion of the tree ring chronology. The final goal is to use the record of tree ring widths to provide reconstructions of past climate.
Data Sets: Tree Ring Widths
There are several data sets available on line from a storage site operated by the NOAA Palaeoclimatology Program. They can be retrieved by searching under the location Canada:Yukon at that site.
The following files containing raw tree widths (location, description and author) are available for northern Yukon sites:
Data Sets: Temperature Reconstructions
Jacoby and D'Arrigo (1989) used tree ring chronologies from 11 different boreal sites distributed across the north from Alaska to Quebec. They developed estimates of past temperatures for the northern hemisphere as a whole covering the period from 1671 to 1973 (Figure 7a in Jacoby and D'Arrigo,1989).
Szeicz and MacDonald (1995) sampled tree rings from white spruce at five sites in the Mackenzie and Franklin Mountains, N.W.T and the Ogilvie and Richardson Mountains in the Yukon. They used a method of analysis (called age dependent modeling) that took into account the age class of the tree used in building the tree width chronologies. Estimates of June-July temperatures spanning the period 1638-1988 are found in Figures 6 and 7a in Szeicz and MacDonald (1995).
Jacoby, G.C. and R. D'Arrigo 1989. Reconstructed northern hemisphere annual temperature since 1671 based on high-latitude tree-ring data from North America. Climatic Change 14: 39-59.
Szeicz, Julian M. and Glen MacDonald 1995. Dendroclimatic reconstruction of summer temperatures in northwestern Canada since A.D. 1638 based on age-dependent modeling. Quaternary Research 44: 257-266.
Written by S. Gilbert, March 1997.