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Rapid Cenozoic glaciation of Antarctica induced by declining atmospheric CO2


The sudden, widespread glaciation of Antarctica and the associated shift towards colder temperatures at the Eocene/Oligocene boundary (34 million years ago) (refs 1–4) is one of the most fundamental reorganizations of global climate known in the geologic record. The glaciation of Antarctica has hitherto been thought to result from the tectonic opening of Southern Ocean gateways, which enabled the formation of the Antarctic Circumpolar Current and the subsequent thermal isolation of the Antarctic continent5. Here we simulate the glacial inception and early growth of the East Antarctic Ice Sheet using a general circulation model with coupled components for atmosphere, ocean, ice sheet and sediment, and which incorporates palaeogeography, greenhouse gas, changing orbital parameters, and varying ocean heat transport. In our model, declining Cenozoic CO2 first leads to the formation of small, highly dynamic ice caps on high Antarctic plateaux. At a later time, a CO2 threshold is crossed, initiating ice-sheet height/mass-balance feedbacks that cause the ice caps to expand rapidly with large orbital variations, eventually coalescing into a continental-scale East Antarctic Ice Sheet. According to our simulation the opening of Southern Ocean gateways plays a secondary role in this transition, relative to CO2 concentration.

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Figure 1: Early Cenozoic ice-free Antarctic topography in metres above sea level.
Figure 2: The transient climate-cryosphere response to a prescribed decline in CO2 from 4 × to 2 × preindustrial atmospheric level over a 10-Myr period.
Figure 3: Ice-surface elevations at instantaneous times during the transition from ‘Greenhouse’ to ‘Icehouse’ conditions in our nominal 10-Myr simulation (Fig. 2a, red curve).


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This material is based upon work supported by the National Science Foundation.

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Correspondence to Robert M. DeConto.

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DeConto, R., Pollard, D. Rapid Cenozoic glaciation of Antarctica induced by declining atmospheric CO2. Nature 421, 245–249 (2003).

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