GEOPHYSICAL MONOGRAPH SERIES, VOL. 193, PP. 57-74, 2011
Modeling Abrupt Climate Change as the Interaction Between Sea Ice Extent and Mean Ocean Temperature Under Orbital Insolation Forcing
The Dansgaard-Oeschger (D-O) temperature fluctuations of the last ice age are a prime example of abrupt climate change in
the paleoclimate record, and they provide evidence that rapid climate change (warming as well as cooling) can occur within
human time scales, making their study highly relevant to the assessment of present and future natural climate variability.
Using conceptual climate models, we show that orbital insolation is likely to play an important role in the timing, amplitude,
and duration of the D-O fluctuations. We are able to replicate key features of the D-O time series, including the abrupt transition
from the last glacial to the present interglacial, using the orbital insolation as the sole external variable forcing of a
simple nonlinear Langevin differential equation. A slightly more complex model based on two nonlinear differential equations
for sea ice extent and mean ocean temperature reasonably reproduces the past 100 kyr of climate fluctuations recorded in the
Greenland ice cores. The model assumes the existence of a free oscillation with a period of ∼1500 years, which is then forced
with white Gaussian noise and the astronomical insolation. The model also reproduces the time histories and the well-known
phase relationship between shallow and deep ocean proxy data, whereby the SST history follows the Greenland climate record,
while the deeper ocean follows the Antarctic's. Comparisons with other low-dimensional models and climate models of intermediate
complexity (ECBILT-CLIO and U-Victoria ESCM) show consistent results.
Citation: Rial, J. A., and