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Rapid Warming of Lake Superior and the role of ice

Rapid Warming of Lake Superior and the role of ice. Jay Austin and Steve Colman Depts. of Physics & Geol. Sci. and Large Lakes Observatory University of Minnesota Duluth MSU ESP Workshop 9 April, 2008. 45006. * 45001. * 45004. * 45006. NOAA’s NDBC buoys. Three buoys in Lake Superior

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Rapid Warming of Lake Superior and the role of ice

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  1. Rapid Warming of Lake Superior andthe role of ice Jay Austin and Steve Colman Depts. of Physics & Geol. Sci. and Large Lakes Observatory University of Minnesota Duluth MSU ESP Workshop 9 April, 2008

  2. 45006 * 45001 * 45004 * 45006

  3. NOAA’s NDBC buoys • Three buoys in Lake Superior • 1979-Present • April-November • AT,WT, WS/WD • Frequently calibrated • (also buoys in other lakes)

  4. NDBC 45001 (Central) Water Temperature (Max. Temperatures) ~0.12C/yr

  5. Regional Air Temperature 15 14 Regional Air Temp, C ~0.06C/yr 13 12 1980 1985 1990 1995 2000 2005

  6. Start of stratified season

  7. Ice Cover in Decline

  8. Summer Overturn date depends on last winter’s ice cover

  9. Summer Water Temperature depends on last winter’s ice cover (1998)

  10. What about wind?(Central Lake Superior, Summer avg.)

  11. Amplification of summer warming • Warmer, windier(?) winters • Less ice cover • Ice-albedo feedback, less ice • Earlier summer turnover • Longer stratified (heating) season • Warmer summer air temps, acting over a longer heating season = amplification

  12. Is the effect strong enough? ~0.11C/yr ~1 ~0.06C/yr ~ -0.015C/% ~ -0.42%/yr ~0.06C/yr ~0.063C/yr

  13. Whitefish Bay

  14. Sault Ste. Marie, 1906-2006

  15. SSM, July-September avg.

  16. Global AT average

  17. Global and Lake Superior

  18. Comparing SSM to globe

  19. Comparing SSM to globe ~0.1C/yr

  20. NDBC 45001 (Central) Water Temperature, July-Sep ~0.12C/yr

  21. Comparing SSM to open lake

  22. Test of Proxy, 1980

  23. One century in the open lake

  24. 147 years of Lake Level

  25. 147 years of Lake Level ????

  26. Fitting it together? • Increased WT • Due to warmer summers, reduced ice cover • Increased Wind Speeds • Due to warmer water Temperatures (?) • Decreased ice cover • Due to milder winters, higher winds (?) • Decreased lake levels • Due to higher WT, higher winds, reduced ice cover • Highly sensitive, non-linear system

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