Fig. 3: Climatic controls on ice sheet resonance.

a Ice volume change under a climate cooling of 4 °C and uniformly strong ocean forcing, both oscillating at 100 kyr periodicity. b Periodogram showing the dominant frequencies in ice volume change during initial third (red), middle third (gold), and final third (blue) of the one million-year long simulation. c Changes in skewness and kurtosis of ice volume change based on a 100 kyr moving window, reflecting increasing asymmetry of ice volume oscillations under increasingly cooler atmosphere. d–f Same as (a–c) but for a simulation in which mean atmospheric temperatures remain constant but ocean forcing increases in strength. g–i Same as (a–c) but for a simulation in which the cooling climate of a–c is combined with the strengthening ocean forcing of d–f. The strongest evidence for both increasing asymmetry as well as harmonic (50 kyr) resonance is seen in the first scenario, suggesting that atmospheric, rather than oceanic, forcing plays the most substantial role in these changes.