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

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

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

12d earlier/century

10d later/century

22d longer/century

Acknowledgements!