NOAA/WDS Paleoclimatology - Model Simulations of Orbital Sensitivity of North American Ice Sheets

STUDY NOTES: Snapshots of a 3-D ice sheet model (Pollard and DeConto, 2012) applied over North America and Greenland, driven either by simply parameterized climate (similarly to Pollard and DeConto, 2009), or by a look-up table of previous Global Climate Model (GCM) solutions (similarly to DeConto and Pollard, 2003), with idealized 40,000-yr sinusoidal climate variations. Main model variables of interest are: h = ice sheet thickness (m) hs = surface elevation (m) hb = bedrock elevation (m) maskwater = 0 for land or grounded ice, 1 for ocean or floating ice. Latitudes of grid points: Every 0.5 degrees, from 20.5 N to 84.5 N (130 points). Longitudes of grid points: Every 1.0 degrees, from 179.5 W to -10.5 W (170 points). Time period: Model integrations of up to 200,000 years, representing idealized orbital forcing with 40,000 year periodicity. Variables are saved every 2000 years, from 0 up to 200000 yr (up to 101 saves). Each NetCDF file contains results for one model experiment, named as follows: fort.92_cyca to fort.92_cych.nc: Using parameterized climate forcing, each with slightly different climate parameters. fort.92_gcmcyc1.nc to fort.92_gcmcyc5.nc: Using GCM lookup-table forcing, each with slightly different look-up parameters, mainly albedo feedback strength. ADDITIONAL REFERENCE: DeConto, R.M. and D. Pollard. 2003. Rapid Cenozoic glaciation of Antarctica induced by declining atmospheric CO2. Nature, 421, 245-249. ADDITIONAL REFERENCE: Pollard, D. and R.M. DeConto. 2009. Modelling West Antarctic ice sheet growth and collapse through the past five million years. Nature, 458, 329-332
ABSTRACT SUPPLIED BY ORIGINATOR: The formulation of a 3-D ice sheet-shelf model is described. The model is designed for long-term continental-scale applications, and has been used mostly in paleoclimatic studies. It uses a hybrid combination of the scaled shallow ice and shallow shelf approximations for ice flow. Floating ice shelves and grounding-line migration are included, with parameterized ice fluxes at grounding lines that allows relatively coarse resolutions to be used. All significant components and parameterizations of the model are described in some detail. Basic results for modern Antarctica are compared with observations, and simulations over the last 5 million years are compared with previously published results. The sensitivity of ice volumes during the last deglaciation to basal sliding coefficients is discussed.