Modeling the History of the

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Modeling the History of the Great Rivers of the
World

• R. A. Bryson, A. H. Ruter, and K. A. McEnaney
• University of Wisconsin-Madison

International Conference on Rivers and
Civilization June 25-28, 2006 in La Crosse, WI
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Archaeoclimatology Macrophysical Climate
Modeling (MCM)

• Based on circulation of the atmosphere
• Jet stream, sub tropical highs, ITC
• Relationship of circulation to local climate
• Circulation controlled by incoming solar
  radiation modulated by volcanic aerosols and
  surface conditions

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Archaeoclimatology Macrophysical Climate
Modeling (MCM)

• Stream discharge integrates climate over the
  catchment
• Modern gauging data as input
• Robust hypotheses

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The Nile River

• The Model matches the proxy record quite well

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Mississippi Amazon Rivers

• Northern vs. Southern Hemisphere circulation

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Congo and Zambezi Rivers

• Some rivers are affected by both northern and
  southern regimes

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Tigris and Euphrates

• Even neighboring rivers have different histories

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Yenisey River, Russia

• The spring freshet has gotten later in Siberia -
  but not linearly so

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Fitzroy River, Australia

• Seasonality Wet vs. Dry Months

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Conclusions

• These models provide specific hypotheses
• Robust compared to field data
• Explanations for timing / size of changes
• Geomorphologically testable
• Global applicability
• Cannot generalize between rivers
• Work is underway on 100-yr resolution
• 250 Rivers modeled. Contact
  rabryson_at_wisc.edu

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Bryson, R. A., K.A. McEnaney, and A.H. Ruter
2006    Modeling the History of the Great Rivers
of the World. Paper presented at the
International Conference on Rivers and
Civilization, June 25-28, La Crosse, WI.