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CAG Quebec 2008 - Prairie drought and tree rings
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CAG Quebec 2008 - Prairie drought and tree rings

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Instrumental records of drought on the Canadian Prairies cover, at most, the last one hundred years. In this presentation, I describe how tree rings can be used to extend our perspective of the ...

Instrumental records of drought on the Canadian Prairies cover, at most, the last one hundred years. In this presentation, I describe how tree rings can be used to extend our perspective of the severity, frequency and causes of Prairie drought

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    CAG Quebec 2008 - Prairie drought and tree rings CAG Quebec 2008 - Prairie drought and tree rings Presentation Transcript

    • Tree rings and Prairie drought Scott St . George Geological Survey of Canada
    • How bad can Prairie drought get?
    • 100 years of stream and lake gauging
    • resource allocation
    • worst-case scenarios
    • 100 years of stream and lake gauging
    • not enough
    • How bad can Prairie drought get?
    • Prairie tree-ring network Northern Saskatchewan Eastern Rockies Northwestern Ontario Southern Manitoba
    • Regional tree growth and inferred summer climate in the Winnipeg River basin, Canada since AD 1783 Scott St. George David Meko Mike Evans in press, Quaternary Research
    • The tree-ring record of summer drought in the Canadian Prairies Scott St. George David Meko Greg Pederson Martin-Phillippe Girardin David Sauchyn Glen MacDonald Jacques Tardif Erik Nielsen Emma Watson Submitted to the Journal of Climate, January 2008
    • 3 Seasonality Accuracy Drought history
    • Seasonality
    • Prairie tree-ring network Northern Saskatchewan Eastern Rockies Northwestern Ontario Southern Manitoba
    • Prairie trees principally track summer precipitation 90 82 Number of sites 75 60 45 30 24 15 7 3 0 19 Autumn Winter Spring Summer Autumn
    • 20
    • Vaganov-Shashkin model of tree-ring formation Gr(t) = g E (t) • min[g T (t), g W (t)] Total Solar radiation Temperature Water balance growth rate growth rate growth rate growth rate
    • INPUT Daily climate data MODEL Vaganov-Shashkin model Synthetic OUT Daily growth rates Cell characteristics ringwidth chronologies
    • INPUT Daily climate data MODEL Vaganov-Shashkin model Synthetic OUT Daily growth rates Cell characteristics ringwidth chronologies
    • Medicine Hat, Alberta Source: Environment Canada, Adjusted Historical Canadian Climate Data, 1895 – 2006
    • 25
    • 26
    • El Niño (1983)
    • ENSO and winter ppt Correlation between CTI and winter precipitation (● = significant at p = 0.05)
    • ENSO and PDSI Correlation between CTI and summer PDSI (● = significant at p = 0.05)
    • Prairie ringwidth records 138 Significant correlation with ENSO 4 Expected from random chance 6.9 31
    • 32
    • Accuracy
    • “ This must be voodoo.” Anonymous water manager
    • How good are drought records from tree rings?
    • Ringwidth as a proxy for ‘Lethbridge’ PDSI
    • 755 m3/s 847 m3/s 809 m3/s 770 m3/s 823 m3/s 787 m3/s 901 m3/s 3
    • Error of the estimate
    • Error of the estimate
    • 755 m3/s 847 m3/s 809 m3/s 770 m3/s 823 m3/s 787 m3/s 901 m3/s 3
    • Very wet Wet Average Dry Very dry
    • Drought history
    • Prairie tree-ring network Northern Saskatchewan Eastern Rockies Northwestern Ontario Southern Manitoba
    • Eastern Rockies drought
    • 1720s
    • 58 oN 56 oN 1718 - 1722 54 oN 52 oN 50 oN 48 oN oW 90 114 oW 9 6o W 108oW 10 2oW Ringwidth anomaly −2 -2 −1 0 0 1 2 +2 (deviations)
    • 49
    • La Niña (1989)
    • ENSO and PDSI Correlation between CTI and summer PDSI (● = significant at p = 0.05)
    • 3 main points
    • Prairie trees record summer drought
    • Pacific Ocean influences are weak
    • How bad can Prairie drought get?
    • worse
    • Tree rings and Prairie drought web.mac.com/scottstgeorge