Simulating the Antarctic ice sheet in the late-Pliocene warm period: PLISMIP-ANT, an ice-sheet model intercomparison project

Abstract

Abstract. In the context of future climate change, understanding the nature and behaviour of ice sheets during warm intervals in Earth history is of fundamental importance. The late Pliocene warm period (also known as the PRISM interval: 3.264 to 3.025 million years before present) can serve as a potential analogue for projected future climates. Although Pliocene ice locations and extents are still poorly constrained, a significant contribution to sea-level rise should be expected from both the Greenland ice sheet and the West and East Antarctic ice sheets based on palaeo sea-level reconstructions. Here, we present results from simulations of the Antarctic ice sheet by means of an international Pliocene Ice Sheet Modeling Intercomparison Project (PLISMIP-ANT). For the experiments, ice-sheet models including the shallow ice and shelf approximations have been used to simulate the complete Antarctic domain (including grounded and floating ice). We compare the performance of six existing numerical ice-sheet models in simulating modern control and Pliocene ice sheets by a suite of five sensitivity experiments. We include an overview of the different ice-sheet models used and how specific model configurations influence the resulting Pliocene Antarctic ice sheet. The six ice-sheet models simulate a comparable present-day ice sheet, considering the models are set up with their own parameter settings. For the Pliocene, the results demonstrate the difficulty of all six models used here to simulate a significant retreat or re-advance of the East Antarctic ice grounding line, which is thought to have happened during the Pliocene for the Wilkes and Aurora basins. The specific sea-level contribution of the Antarctic ice sheet at this point cannot be conclusively determined, whereas improved grounding line physics could be essential for a correct representation of the migration of the grounding-line of the Antarctic ice sheet during the Pliocene.

Sea-level response to melting of Antarctic ice shelves on multi-centennial timescales with the fast Elementary Thermomechanical Ice Sheet model (f.ETISh v1.0)

“…3), with a melt scaling factor of F melt = 0.125, from all other ice shelves that have a scaling factor of F melt = 1. A similar approach has been taken by many other ice sheet models cited in de Boer et al (2015).…”

“…Surface mass balance is then the sum of the different components, i.e.ȧ = P − S, where S = 0.005× PDD is the surface melt rate. Melting underneath the floating ice shelves is often based on parametrizations that relate sub-shelf melting to ocean temperature and ice shelf depth (Beckmann and Goosse, 2003;Holland et al, 2008), either in a linear or a quadratic way Pollard and DeConto, 2012a;de Boer et al, 2015;DeConto and Pollard, 2016). This leads to higher melt rates close to the grounding line, as the ice shelf bottom is the lowest.…”

“…The parametrizations of T s and P can easily be replaced by values that stem from global circulation models, with appropriate corrections for surface elevation (e.g. de Boer et al, 2015).…”

Modelling present-day basal melt rates for Antarctic ice shelves using a parametrization of buoyant meltwater plumes

“…State-of-the-art ice-sheet models for large-scale climate simulations (see e.g. de Boer et al, 2015) provide a complete description of the flow and thermodynamics of ice. However, due to the complex nature of the system and high computational cost of climate simulations, these models inevitably contain approximations and parametrizations of many physical processes, among which basal melting is no exception.…”

Progress in Numerical Modeling of Antarctic Ice-Sheet Dynamics

“…Finally, understanding the past to give insights into the future has motivated the PLISMIP-ANT intercomparison project [20], focussing on the Antarctic ice-sheet behavior during the late-Pliocene warm period.…”