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Proc Natl Acad Sci U S A. 2016 Mar 29;113(13):3459-64. doi: 10.1073/pnas.1516130113. Epub 2016 Feb 22.

Dynamic Antarctic ice sheet during the early to mid-Miocene.

Author information

1
Climate System Research Center, University of Massachusetts, Amherst, MA 01003; egw.gasson@gmail.com.
2
Climate System Research Center, University of Massachusetts, Amherst, MA 01003;
3
Earth and Environmental Systems Institute, Pennsylvania State University, State College, PA 16802;
4
GNS Science, Avalon, Lower Hutt 5011, New Zealand.

Abstract

Geological data indicate that there were major variations in Antarctic ice sheet volume and extent during the early to mid-Miocene. Simulating such large-scale changes is problematic because of a strong hysteresis effect, which results in stability once the ice sheets have reached continental size. A relatively narrow range of atmospheric CO2 concentrations indicated by proxy records exacerbates this problem. Here, we are able to simulate large-scale variability of the early to mid-Miocene Antarctic ice sheet because of three developments in our modeling approach. (i) We use a climate-ice sheet coupling method utilizing a high-resolution atmospheric component to account for ice sheet-climate feedbacks. (ii) The ice sheet model includes recently proposed mechanisms for retreat into deep subglacial basins caused by ice-cliff failure and ice-shelf hydrofracture. (iii) We account for changes in the oxygen isotopic composition of the ice sheet by using isotope-enabled climate and ice sheet models. We compare our modeling results with ice-proximal records emerging from a sedimentological drill core from the Ross Sea (Andrill-2A) that is presented in a companion article. The variability in Antarctic ice volume that we simulate is equivalent to a seawater oxygen isotope signal of 0.52-0.66‰, or a sea level equivalent change of 30-36 m, for a range of atmospheric CO2 between 280 and 500 ppm and a changing astronomical configuration. This result represents a substantial advance in resolving the long-standing model data conflict of Miocene Antarctic ice sheet and sea level variability.

KEYWORDS:

Antarctic ice sheet; Miocene; oxygen isotopes; sea level

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