Towards a Transient, Coupled 3D Ice Sheet – Climate
Simulation of the Last Glacial Cycle
M. Heinemann1, A. Timmermann1, O. Elison Timm1, F. Saito2, and A. Abe-Ouchi2
1IPRC, 2JAMSTEC
ice thickness [km]
6
4
2
0
Fig. 2: Simulated present-day ice sheets (left), and how the presentday ice sheets would look like without post-LGM greenhouse gas
increase, according to our model (right).
b
A new Earth System model named iLove (ice sheet LOVECLIM)
has been developed. It is the first coupled ice sheet – climate
model with 3D atmosphere and ocean components to simulate
the Last Glacial Cycle (Fig. 1a) driven with continuously evolving
CO2 concentrations and orbital forcing.
Glacial inception is characterized by a delicate balance between
snow accumulation and ablation, basal melting, and calving (Fig.
1b).
Fig. 1: a) Simulated Northern Hemisphere ice sheet volume
in meter sea level equivalent (msle). b) Ice sheet volume rate
of change (dV/dt) due to sources (accumulation, reddish),
and due to sinks (blue); obliquity and precession are shown
for reference only, not to scale. Grey shading and crosses
indicate paleo-reconstructions.
According to iLove, the Milankovitch theory (“orbital changes plus
albedo feedback cause ice ages”) is insufficient to explain the
Last Glacial Cycle. Atmospheric CO2 feedbacks are necessary.
Without increased CO2 after the Last Glacial Maximum (LGM),
we would still live in a glacial climate (Fig. 2), indicating that the
carbon cycle response to orbital forcing is crucial to our
understanding of glacial cycles.