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Thursday, December 25, 2008

D. Pollard & R. M. Deconto (2008), Modeling West Antarctic Ice Sheet Growth and Retreat Through the Last 5 Million Years

American Geophysical Union, Fall Meeting 2008, abstract #C34B-02; published December 2008

Modeling West Antarctic Ice Sheet Growth and Retreat Through the Last 5 Million Years

D. Pollard (Pennsylvania State University, Earth and Environmental Systems Institute, 2217 Earth-Engineering Science Bldg., University Park, PA 16802, U.S.A.; e-mail: and R. M. DeConto (University of Massachusetts, Department of Geosciences, 233 Morrill Science Center, Amherst, MA 01003, U.S.A.; e-mail:

The West Antarctic Ice Sheet, grounded mostly below sea level and fringed by floating ice shelves, is considered to be vulnerable to future anthropogenic warming. However, projections of its future behavior are hampered by limited understanding of past variations and the main forcing mechanisms. Here a combined ice sheet-shelf model with imposed grounding-line fluxes following C. Schoof (J. Geophys. Res., 2007) is used to simulate Antarctic variations over the last 5 million years. We argue that oceanic melting below ice shelves is an important long-term forcing, controlled mainly by far-field influences that can be correlated with deep-sea- core d18O records. Model West Antarctic configurations range between full glacial extents with grounding lines near the continental shelf break, intermediate states similar to modern, and brief collapses to isolated ice caps on small West Antarctic islands. Transitions between these states can be relatively rapid, taking one to several thousand years. Several aspects of our simulation agree with a sediment record recently recovered beneath the Ross Ice Shelf by ANDRILL (MIS AND-1B core), including a long-term trend from more frequently collapsed to more glaciated states, and brief but dramatic collapses at Marine Isotope Stage 31 (~1 Ma) and other super-interglacials. Higher-resolution nested simulations over the Ross Embayment resolve Siple Coast ice streams, Transantarctic outlet glaciers, and details of shelf flow. Correlations between modeled local conditions near the AND-1B core site and the overall West Antarctic state are examined, along with implications for the AND-1B lithologic record.

Link to abstract:

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