title: Dynamic Antarctic ice sheet during the early to mid-Miocene.
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.
authors.affiliation: Climate System Research Center, University of Massachusetts, Amherst, MA 01003; egw.gasson@gmail.com.
authors.forename: Edward
authors.identifier: http://orcid.org/0000-0003-4653-6217
authors.initials: E
authors.lastname: Gasson
authors.affiliation: Climate System Research Center, University of Massachusetts, Amherst, MA 01003;
authors.forename: Robert M
authors.initials: RM
authors.lastname: DeConto
authors.affiliation: Earth and Environmental Systems Institute, Pennsylvania State University, State College, PA 16802;
authors.forename: David
authors.initials: D
authors.lastname: Pollard
authors.affiliation: GNS Science, Avalon, Lower Hutt 5011, New Zealand.
authors.forename: Richard H
authors.initials: RH
authors.lastname: Levy
keywords: Antarctic ice sheet; Miocene; oxygen isotopes; sea level