Modeling the History of the ‘Great Rivers’ of the World R. A. Bryson, A. H. Ruter, and K. A. McEnaney University of Wisconsin-Madison 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

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 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

Archaeoclimatology: Macrophysical Climate Modeling (MCM) Stream discharge integrates climate over the catchment Modern gauging data as input Robust hypotheses Stream discharge integrates climate over the catchment Modern gauging data as input Robust hypotheses

The Nile River The Model matches the proxy record quite well

Mississippi & Amazon Rivers Northern vs. Southern Hemisphere circulation

Some rivers are affected by both northern and southern regimes Congo and Zambezi Rivers

Tigris and Euphrates Even neighboring rivers have different histories

Yenisey River, Russia The spring freshet has gotten later in Siberia - but not linearly so

Fitzroy River, Australia Seasonality: Wet vs. Dry Months

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: 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: Preliminary 100-yr resolution (Calibrated Calendar Years)

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.