Embed Size (px)
DESCRIPTION
I've been asked to give a presentation at a workshop to be held in Alberta in March. The workshop will revolve mainly around the use of tree rings and other natural 'proxy' records to water issues in the Canadian Prairie provinces. I'll be presenting material drawn from the last chapter of my doctoral dissertation, and will talk about the strengths and limitations of tree-ring records as indicators of past drought. The audience will include between 50 and 100 water managers from the region, and for many of them, the workshop will be their first exposure to tree rings and other forms of paleoclimatology. I think it will be in their best interest (and mine) that the scientific presentations focus more on big-picture ideas and less on technical details and methodology. With an eye towards getting my point across more effectively, I've worked up a set of slides in the 'Presentation Zen' style. I've included more photos than I have in previous presentations, and have also tried to swap out complex journal-style diagrams and replace them with simpler graphics. I'm excited (and a little nervous) to see how the presentation is received - I imagine its style will be quite different from the other talks in the workshop. I've posted the slides at Slideshare.net, and would appreciate any comments or suggestions - the workshop is not for another six weeks, so I have plenty of time left to tweak or change my plans.
Citation preview
Tree Rings and DroughtPast drought on the Canadian Prairies
Scott St . GeorgeGeological Survey of Canada
Prairie tree-ring network, ca. 1996
3
Fort Dufferin, Manitoba
6
4,000 year-old river logs
Prairie tree-ring network
Eastern Rockies
Northern Saskatchewan
Southern Manitoba
Northwestern Ontario
4Characteristics ofPrairie tree rings
The tree-ring record of summer drought in the Canadian Prairies
Scott St. GeorgeDavid MekoMartin-Phillippe GirardinGlen MacDonaldErik Nielsen
Greg PedersonDavid SauchynJacques TardifEmma Watson
Submitted to the Journal of Climate, January 2008
Tree age
Photo: Tom Harlan
Bristlecone pine4,844 years
Source: OLDLIST
Photo: Peter Kelly
Eastern white cedar1,653 years
Source: OLDLIST
Eastern white pine290 years
Source: M. Girardin
Bur oak279 years
Photo: Greg Pederson
Limber pine846 years
Source: G. Pederson
Photo: julie & fanu16
Richard I of England
S. Alberta
N. Saskatchewan
S. Manitoba
NW Ontario
0 125 250 375 500
225
485
169
480
Years
Length of regional records
Seasonality
”
“The trees composing the forest rejoice and lament with its successes and failures and carry year by year something of its story in their annual rings. A.E. Douglass
200
10
20
30
40
50
60
70
80
90
Autumn Winter Spring Summer Autumn
82
24
73
Site
sDominant seasonal signals
21
22
Source: Environment Canada, Adjusted Historical Canadian Climate Data, 1895 – 2006
Medicine Hat, Alberta
24
Effectiveness
Dendrohydrology works best where it’s
dry...
and not so well where it’s
wet
Ringwidth as a proxy for ‘Lethbridge’ PDSI
Ringwidth as a proxy for ‘Dryden’ PDSI
Uncertainty
755 m3/s847 m3/s809 m3/s770 m3/s823 m3/s787 m3/s901 m3/s840 m3/s
“Trees are not thermometers or raingauges.”
Keith Briffa and colleagues
Quantitative drought estimates
Quantitative drought estimates
Can we do better? Absolutely!
Photo: Emma Watson
38
Photo: New York Times
Focus on long-term drought
0%
25%
50%
75%
100%
Single Year 5-Year Average
43%60%
57%
40%
Expl
aine
d va
rian
ce
Courtesy Keith Lombardo
Measure other stuffWood chemistry
Stable isotopes
Wood density
Wood anatomy
Prairie tree rings
41
& drought
Photo: Monceau
web.mac.com/scottstgeorge
