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.
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.