Transcript Using a climate change story to teach about large

Using a climate change story to
teach about large lake processes
Jay Austin
Associate Professor
Large Lakes Observatory /Department of Physics
University 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
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
* 45001
* 45004
* 45006
NDBC 45001 (Central)
Water Temperature, July-Sep
~0.1C/yr
NDBC 45001 (Central)
Water Temperature
(Max.
Temperatures)
~0.12C/yr
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 watersurface layer very deep- often
comprises entire water column
Start of Stratified season
Central Buoy WT, 2006
Max temp., mid August
Fall Cooling
Rapid warming
Slow warming
Buoy recovered
Summer Overturn
Two extremes1996 (cold) and 1998 (warm)
1998
1996
Ice Cover in Decline
Magnuson et al. 2000
Formation dates
Breakup dates
Magnuson et al., 2000
Howk 2008
Summer Overturn date depends
on last winter’s ice cover
Summer Water Temperature
depends on last winter’s ice cover
(1998)
Length of season
10d later/century
12d earlier/century
22d longer/century
Acknowledgements!