The impact of dynamic topography change on Antarctic ice sheet stability during the mid-Pliocene warm period

The evolution of the Antarctic ice sheet during the mid-Pliocene warm period (MPWP) remains uncertain and has important implications for our understanding of ice sheet response to modern global warming. The extent to which marine-based sectors of the East Antarctic Ice Sheet (EAIS) retreated during the MPWP is particularly contentious, with geological observations and geochemical analyses being cited to argue for either a relatively minor or a significant ice sheet retreat in response to mid-Pliocene warming. The stability of marine-based ice sheets is intimately linked to bedrock elevation at their grounding lines, and previous ice sheet modeling assumed that Antarctic bedrock elevation during the MPWP was the same as today with the exception of a correction for the crustal response to ice loading. However, various processes may have perturbed bedrock elevation over the past 3 m.y., most notably vertical deflections of the crust driven by mantle convective flow, or dynamic topography. Here we present simulations of mantle convective flow that are consistent with a wide range of present-day observables and use them to predict changes in dynamic topography and reconstruct bedrock elevations during the MPWP. We incorporate these elevations into a simulation of the Antarctic ice sheet during the MPWP and find that the correction for dynamic topography change has a significant effect on the stability of the EAIS within the marine-based Wilkes Basin, with the ice margin in that sector retreating considerably further inland (200–560 km) relative to simulations that do not include this correction for bedrock elevation.

[1]  M. Gurnis,et al.  Constraining mantle density structure using geological evidence of surface uplift rates: The case of the African Superplume , 2000 .

[2]  David Pollard,et al.  Description of a hybrid ice sheet-shelf model, and application to Antarctica , 2012 .

[3]  M. Kurz,et al.  Age and uplift rates of Sirius Group sediments in the Dominion Range, Antarctica, from surface exposure dating and geomorphology , 2004 .

[4]  P. Barrett,et al.  Antarctic topography at the Eocene–Oligocene boundary , 2012 .

[5]  Martin Kronbichler,et al.  High accuracy mantle convection simulation through modern numerical methods , 2012 .

[6]  Zhonghui Liu,et al.  High Earth-system climate sensitivity determined from Pliocene carbon dioxide concentrations , 2010 .

[7]  N. Mortimer,et al.  Basal Adare volcanics, Robertson Bay, North Victoria Land, Antarctica: Late Miocene intraplate basalts of subaqueous origin , 2007 .

[8]  M. Gurnis.  Bounds on global dynamic topography from Phanerozoic flooding of continental platforms , 1990, Nature.

[9]  Bo Sun,et al.  Bedmap2: improved ice bed, surface and thickness datasets for Antarctica , 2012 .

[10]  P. Valdes,et al.  Characterizing ice sheets during the Pliocene: evidence from data and models , 2007 .

[11]  Robert B. Dunbar,et al.  Dynamic behaviour of the East Antarctic ice sheet during Pliocene warmth , 2013 .

[12]  D. Sugden,et al.  The Case for a Stable East Antarctic Ice Sheet: The Background , 1993 .

[13]  A. Abe‐Ouchi,et al.  Simulating the Antarctic ice sheet in the late-Pliocene warm period: PLISMIP-ANT, an ice-sheet model intercomparison project , 2014 .

[14]  H. Dowsett,et al.  Pliocene three-dimensional global ocean temperature reconstruction , 2009 .

[15]  N. Simmons,et al.  Constraints on Seismic Models from Other Disciplines - Constraints on 3-D Seismic Models from Global Geodynamic Observables: Implications for the Global Mantle Convective Flow , 2013 .

[16]  G. Denton,et al.  Minimal Pliocene-Pleistocene uplift of the dry valleys sector of the Transantarctic Mountains: A key parameter in ice-sheet reconstructions , 1993 .

[17]  J. H. Mercer,et al.  Cenozoic marine sedimentation and ice-volume variation on the East Antarctic craton , 1984 .

[18]  Richard B. Alley,et al.  Potential Antarctic Ice Sheet retreat driven by hydrofracturing and ice cliff failure , 2015 .

[19]  D. Pollard,et al.  A 3-D coupled ice sheet – sea level model applied to Antarctica through the last 40 ky , 2013 .

[20]  G. Kuhn,et al.  Obliquity-paced Pliocene West Antarctic ice sheet oscillations , 2009, Nature.

[21]  R. McKay,et al.  Orbital forcing of the East Antarctic ice sheet during the Pliocene and Early Pleistocene , 2014 .

[22]  S. Rahmstorf,et al.  Sea-level rise due to polar ice-sheet mass loss during past warm periods , 2015, Science.

[23]  C. Faccenna,et al.  Recent extension driven by mantle upwelling beneath the Admiralty Mountains (East Antarctica) , 2008 .

[24]  N. Simmons,et al.  Joint seismic, geodynamic and mineral physical constraints on three-dimensional mantle heterogeneity: Implications for the relative importance of thermal versus compositional heterogeneity , 2009 .

[25]  Mark Williams,et al.  The PRISM3D paleoenvironmental reconstruction , 2010 .

[26]  N. Simmons,et al.  Joint seismic-geodynamic-mineral physical modelling of African geodynamics: A reconciliation of deep-mantle convection with surface geophysical constraints , 2010 .

[27]  R. DeConto,et al.  Modeling Antarctic ice sheet and climate variations during Marine Isotope Stage 31 , 2012 .

[28]  J. Mitrovica,et al.  Lateral variations in mantle rheology: implications for convection related surface observables and inferred viscosity models , 2007 .

[29]  S. S. Rai,et al.  Seismic imaging of the upper mantle under the Erebus hotspot in Antarctica , 2009 .

[30]  C. Beaumont,et al.  Tilting of continental interiors by the dynamical effects of subduction: Tectonics , 1989 .

[31]  C. Schoof.  Ice sheet grounding line dynamics: Steady states, stability, and hysteresis , 2007 .

[32]  David Pollard,et al.  Modelling West Antarctic ice sheet growth and collapse through the past five million years , 2009, Nature.

[33]  Timothy H. Dixon,et al.  REVEL: A model for Recent plate velocities from space geodesy , 2002 .