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 severity, frequency and causes of Prairie drought

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CAG Quebec 2008 - Prairie drought and tree rings

  1. 1. Tree rings and Prairie drought Scott St . George Geological Survey of Canada
  2. 2. How bad can Prairie drought get?
  3. 3. 100 years of stream and lake gauging
  4. 4. resource allocation
  5. 5. worst-case scenarios
  6. 6. 100 years of stream and lake gauging
  7. 7. not enough
  8. 8. How bad can Prairie drought get?
  9. 9. Prairie tree-ring network Northern Saskatchewan Eastern Rockies Northwestern Ontario Southern Manitoba
  10. 10. 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
  11. 11. 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
  12. 12. 3 Seasonality Accuracy Drought history
  13. 13. Seasonality
  14. 14. Prairie tree-ring network Northern Saskatchewan Eastern Rockies Northwestern Ontario Southern Manitoba
  15. 15. 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
  16. 16. 20
  17. 17. 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
  18. 18. INPUT Daily climate data MODEL Vaganov-Shashkin model Synthetic OUT Daily growth rates Cell characteristics ringwidth chronologies
  19. 19. INPUT Daily climate data MODEL Vaganov-Shashkin model Synthetic OUT Daily growth rates Cell characteristics ringwidth chronologies
  20. 20. Medicine Hat, Alberta Source: Environment Canada, Adjusted Historical Canadian Climate Data, 1895 – 2006
  21. 21. 25
  22. 22. 26
  23. 23. El Niño (1983)
  24. 24. ENSO and winter ppt Correlation between CTI and winter precipitation (● = significant at p = 0.05)
  25. 25. ENSO and PDSI Correlation between CTI and summer PDSI (● = significant at p = 0.05)
  26. 26. Prairie ringwidth records 138 Significant correlation with ENSO 4 Expected from random chance 6.9 31
  27. 27. 32
  28. 28. Accuracy
  29. 29. “ This must be voodoo.” Anonymous water manager
  30. 30. How good are drought records from tree rings?
  31. 31. Ringwidth as a proxy for ‘Lethbridge’ PDSI
  32. 32. 755 m3/s 847 m3/s 809 m3/s 770 m3/s 823 m3/s 787 m3/s 901 m3/s 3
  33. 33. Error of the estimate
  34. 34. Error of the estimate
  35. 35. 755 m3/s 847 m3/s 809 m3/s 770 m3/s 823 m3/s 787 m3/s 901 m3/s 3
  36. 36. Very wet Wet Average Dry Very dry
  37. 37. Drought history
  38. 38. Prairie tree-ring network Northern Saskatchewan Eastern Rockies Northwestern Ontario Southern Manitoba
  39. 39. Eastern Rockies drought
  40. 40. 1720s
  41. 41. 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)
  42. 42. 49
  43. 43. La Niña (1989)
  44. 44. ENSO and PDSI Correlation between CTI and summer PDSI (● = significant at p = 0.05)
  45. 45. 3 main points
  46. 46. Prairie trees record summer drought
  47. 47. Pacific Ocean influences are weak
  48. 48. How bad can Prairie drought get?
  49. 49. worse
  50. 50. Tree rings and Prairie drought web.mac.com/scottstgeorge

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