Presentation on theme: "What drives the ice age cycles?. Milankovitch Theory of orbital forcing of ice sheets Tilt variations eccentricity variations precession of perihelion."— Presentation transcript:
What drives the ice age cycles?
Milankovitch Theory of orbital forcing of ice sheets Tilt variations eccentricity variations precession of perihelion
Precession of Solstices (or Perihelion)
Precession of Solstices
Precession & eccentricity
Changes in summer insolation
Changes in winter insolation
Low High Latitude NH summer insolation Allows ice sheets to grow from year to year
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.
Low insolation High insolation
Solar insolation Surface temp Ice volume Ice height albedo Southern edge Base ablation Bedrock sinking
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.