Using a climate change story to teach about large lake processes
Jay AustinAssociate Professor
Large Lakes Observatory /Department of PhysicsUniversity of Minnesota Duluth
Teaching Climate Change: Lessons from the Past
20 June, 2012
The Past and Present• The Past: What sorts of records allow
us to reliably look into the past?• The Present: How do we understand how
Lake Superior is changing right now?
Sault Ste. Marie, 1906-2006(“the past”)
SSM, July-September avg.
SSM, July-September avg.
Global AT average
Comparing SSM to globe
Comparing SSM to globe
~0.1C/yr
Regional Air Temperature Anomaly
~0.06C/yr
NOAA’s NDBC buoys(“The Present”)
• Three buoys in Lake Superior
• 1979-Present• April-November• AT,WT, WS/WD• (also buoys in other
lakes)
45006
* 45006
* 45001
* 45004
NDBC 45001 (Central) Water Temperature, July-Sep
~0.1C/yr
NDBC 45001 (Central) Water Temperature
~0.12C/yr
(Max. Temperatures)
Lakes around the world
Freshwater Density
Summer stratification
Warm water overlies cooler water- surface layer can be relatively thin (~10-30m)
Winter Stratification
Cool water overlies warmer water- surface layer very deep- often comprises entire water column
Start of Stratified season
Central Buoy WT, 2006
Slow warmingSummer Overturn
Rapid warming
Max temp., mid August
Fall Cooling
Buoy recovered
Two extremes- 1996 (cold) and 1998 (warm)
1998
1996
Ice Cover in Decline
Magnuson et al. 2000
Formation dates
Breakup dates
Magnuson et al., 2000
Summer Overturn date depends on last winter’s ice cover
Summer Water Temperature depends on last winter’s ice cover
(1998)
Length of season
12d earlier/century
10d later/century
22d longer/century
Acknowledgements!