Dynamic Antarctic ice sheet during the early to mid-Miocene

• Published in: Proceedings of the National Academy of Sciences
• Main Authors: Gasson, Edward, DeConto, Robert M., Pollard, David, Levy, Richard H.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2016
• Subjects: Antarctic ice sheet; Miocene; Oxygen isotopes; Sea level; Antarc*; Antarctic; Ice Sheet; Ice Shelf; Ross Sea
• Online Access: https://hdl.handle.net/1983/898df9bb-9315-4ebf-aa23-f761e0a93c1b; https://research-information.bris.ac.uk/en/publications/898df9bb-9315-4ebf-aa23-f761e0a93c1b; https://doi.org/10.1073/pnas.1516130113; http://www.scopus.com/inward/record.url?scp=84962183165&partnerID=8YFLogxK

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 CO 2 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 CO 2 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.