CAG Quebec 2008 - Prairie drought and tree rings

Slide 1: Tree rings and Prairie drought Scott St . George Geological Survey of Canada

Slide 2: How bad can Prairie drought get?

Slide 3: 100 years of stream and lake gauging

Slide 4: resource allocation

Slide 5: worst-case scenarios

Slide 9: 100 years of stream and lake gauging

Slide 10: not enough

Slide 12: How bad can Prairie drought get?

Slide 13: Prairie tree-ring network Northern Saskatchewan Eastern Rockies Northwestern Ontario Southern Manitoba

Slide 14: 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

Slide 15: 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

Slide 16: 3 Seasonality Accuracy Drought history

Slide 17: Seasonality

Slide 18: Prairie tree-ring network Northern Saskatchewan Eastern Rockies Northwestern Ontario Southern Manitoba

Slide 19: 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

Slide 20: 20

Slide 21: 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

Slide 22: INPUT Daily climate data MODEL Vaganov-Shashkin model Synthetic OUT Daily growth rates Cell characteristics ringwidth chronologies

Slide 23: INPUT Daily climate data MODEL Vaganov-Shashkin model Synthetic OUT Daily growth rates Cell characteristics ringwidth chronologies

Slide 24: Medicine Hat, Alberta Source: Environment Canada, Adjusted Historical Canadian Climate Data, 1895 – 2006

Slide 25: 25

Slide 26: 26

Slide 28: El Niño (1983)

Slide 29: ENSO and winter ppt Correlation between CTI and winter precipitation (● = significant at p = 0.05)

Slide 30: ENSO and PDSI Correlation between CTI and summer PDSI (● = significant at p = 0.05)

Slide 31: Prairie ringwidth records 138 Significant correlation with ENSO 4 Expected from random chance 6.9 31

Slide 32: 32

Slide 34: Accuracy

Slide 35: “ This must be voodoo.” Anonymous water manager

Slide 36: How good are drought records from tree rings?

Slide 37: Ringwidth as a proxy for ‘Lethbridge’ PDSI

Slide 38: 755 m3/s 847 m3/s 809 m3/s 770 m3/s 823 m3/s 787 m3/s 901 m3/s 3

Slide 39: Error of the estimate

Slide 40: Error of the estimate

Slide 41: 755 m3/s 847 m3/s 809 m3/s 770 m3/s 823 m3/s 787 m3/s 901 m3/s 3

Slide 42: Very wet Wet Average Dry Very dry

Slide 44: Drought history

Slide 45: Prairie tree-ring network Northern Saskatchewan Eastern Rockies Northwestern Ontario Southern Manitoba

Slide 46: Eastern Rockies drought

Slide 47: 1720s

Slide 48: 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)

Slide 49: 49

Slide 51: La Niña (1989)

Slide 52: ENSO and PDSI Correlation between CTI and summer PDSI (● = significant at p = 0.05)

Slide 54: 3 main points

Slide 55: Prairie trees record summer drought

Slide 56: Pacific Ocean influences are weak

Slide 57: How bad can Prairie drought get?

Slide 58: worse

Slide 59: Tree rings and Prairie drought web.mac.com/scottstgeorge