1. What drives the ice age cycles?

2. Milankovitch Theory of orbital forcing of ice sheets
Tilt variations
eccentricity variations
precession of perihelion

3. Axial Tilt

4. Axial Tilt

5. Eccentricity

6. Eccentricity

7. Precession of Solstices (or Perihelion)

8. Precession of Solstices

9. Precession

10. Precession & eccentricity

11. Changes in summer insolation

12. Changes in winter insolation

13. Low High Latitude NH summer insolation Allows ice sheets to grow from year to year

14. Milankovitch Theory:
Variations in high latitude (65 N) summer insolation combine with climate system feednack processes drives ice sheet growth and retreat on time scales of 10,000 yrs to 100,000 yrs.

15. High insolation
Low insolation

16. Solar insolation
Surface temp
albedo
Ice volume
Bedrock
sinking
Southern edge
Ice height
Base ablation

18. When high latitude NH summer insolation is below the threshold ice sheets grow slowly. When high latitude NH summer insolation is above the threshold ice sheets quickly retreat.  a sawtooth pattern. Gradual buildup and rapid deglaciation.