What drives the ice age cycles?. Milankovitch Theory of orbital forcing of ice sheets Tilt variations eccentricity variations precession of perihelion.

What drives the ice age cycles?

Milankovitch Theory of orbital forcing of ice sheets

Tilt variationseccentricity variationsprecession of perihelion

Axial Tilt

Axial Tilt

Eccentricity

Eccentricity

Precession of Solstices (or Perihelion)

Precession of Solstices

Precession

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

Bedrocksinking

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.