# Model Simulations of Orbital Sensitivity of North American Ice Sheets #----------------------------------------------------------------------- # World Data Center for Paleoclimatology, Boulder # and # NOAA Paleoclimatology Program #----------------------------------------------------------------------- # NOTE: Please cite original reference when using these data, # plus the Online Resource and date accessed. # # Description/Documentation lines begin with # # Data lines have no # # # Online Resource: http://hurricane.ncdc.noaa.gov/pls/paleox/f?p=519:1:::::P1_STUDY_ID:13440 #-------------------- # Archive/proxy: # Paleoclimatic Modeling #-------------------- # Contribution Date # Date: 10-24-2012 #-------------------- # Title # Model Simulations of Orbital Sensitivity of North American Ice Sheets #-------------------- # Investigators: Pollard, D. and R.M. DeConto #-------------------- # Description and 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 # #-------------------- # Publication/Citation # Authors: Pollard, D. and R.M. DeConto # Journal Name: Geoscientific Model Development # Published Title: Description of a hybrid ice sheet-shelf model, and application to Antarctica # Published Date: 10-17-2012 # DOI: 10.5194/gmd-5-1273-2012 # Abstract: 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. # #--------------------- # Funding Agency # Funding Agency Name: US National Science Foundation # Grant: 0902870 #-------------------- # Site Information # Name: # Region: # Country: # Northmost Latitude: # Southmost Latitude: # Eastmost Longitute: # Westmost Longitute: # Elevation: #------------------ # Data Collection # Core Name: # First Year: # Last Year: # Time Unit: # Core Length: # Notes: #------------------ # Chronology # # #------------------ # Variables # float x1(x1) ; x1:long_name = "x coordinate, h,v-grids" ; x1:units = "km" ; x1:FORTRAN_format = "f8.3" ; float y1(y1) ; y1:long_name = "y coordinate, h,u-grids" ; y1:units = "km" ; y1:FORTRAN_format = "f8.3" ; float x0(x0) ; x0:long_name = "x coordinate, u-grid" ; x0:units = "km" ; x0:FORTRAN_format = "f8.3" ; float y0(y0) ; y0:long_name = "y coordinate, v-grid" ; y0:units = "km" ; y0:FORTRAN_format = "f8.3" ; float z(z) ; z:long_name = "z coordinate within ice" ; z:units = "(ztop-z)/h, 0 to 1" ; z:FORTRAN_format = "f8.3" ; float time(time) ; time:long_name = "time (-=BP, +=AP)" ; time:units = "years" ; time:FORTRAN_format = "f12.3" ; float vershis(time) ; vershis:long_name = "history file version number" ; vershis:units = "none" ; vershis:FORTRAN_format = "e13.5" ; float sealev(time) ; sealev:long_name = "sea level" ; sealev:units = "m" ; sealev:FORTRAN_format = "e13.5" ; float toti(time) ; toti:long_name = "ice volume" ; toti:units = "m3" ; toti:FORTRAN_format = "e13.5" ; float totig(time) ; totig:long_name = "grounded ice volume" ; totig:units = "m3" ; totig:FORTRAN_format = "e13.5" ; float totif(time) ; totif:long_name = "floating ice volume" ; totif:units = "m3" ; totif:FORTRAN_format = "e13.5" ; float tota(time) ; tota:long_name = "ice area" ; tota:units = "m2" ; tota:FORTRAN_format = "e13.5" ; float totag(time) ; totag:long_name = "grounded ice area" ; totag:units = "m2" ; totag:FORTRAN_format = "e13.5" ; float totaf(time) ; totaf:long_name = "floating ice area" ; totaf:units = "m2" ; totaf:FORTRAN_format = "e13.5" ; float alatd(y1, x1) ; alatd:long_name = "latitude, h-grid" ; alatd:units = "deg N" ; alatd:FORTRAN_format = "e13.5" ; float alond(y1, x1) ; alond:long_name = "longitude, h-grid" ; alond:units = "deg E" ; alond:FORTRAN_format = "e13.5" ; float darea(y1, x1) ; darea:long_name = "cell area, h-grid" ; darea:units = "m^2" ; darea:FORTRAN_format = "e13.5" ; float h(time, y1, x1) ; h:long_name = "ice thickness" ; h:units = "m" ; h:FORTRAN_format = "e13.5" ; float hb(time, y1, x1) ; hb:long_name = "bed elevation" ; hb:units = "m" ; hb:FORTRAN_format = "e13.5" ; float hbsd(time, y1, x1) ; hbsd:long_name = "standard deviation bed elevation" ; hbsd:units = "m" ; hbsd:FORTRAN_format = "e13.5" ; float hbslope(time, y1, x1) ; hbslope:long_name = "mean subgrid slope amplitude" ; hbslope:units = "m" ; hbslope:FORTRAN_format = "e13.5" ; float topbedeq(time, y1, x1) ; topbedeq:long_name = "equilibrium bedrock elevation" ; topbedeq:units = "m" ; topbedeq:FORTRAN_format = "e13.5" ; float hs(time, y1, x1) ; hs:long_name = "surface elevation" ; hs:units = "m" ; hs:FORTRAN_format = "e13.5" ; float deflect(time, y1, x1) ; deflect:long_name = "lithospheric deflection" ; deflect:units = "m" ; deflect:FORTRAN_format = "e13.5" ; float geoflux(time, y1, x1) ; geoflux:long_name = "geothermal heat flux" ; geoflux:units = "J/m2/a" ; geoflux:FORTRAN_format = "e13.5" ; float budgall(time, y1, x1) ; budgall:long_name = "net budget" ; budgall:units = "m/y" ; budgall:FORTRAN_format = "e13.5" ; float budgsnow(time, y1, x1) ; budgsnow:long_name = "snowfall" ; budgsnow:units = "m/y" ; budgsnow:FORTRAN_format = "e13.5" ; float budgrain(time, y1, x1) ; budgrain:long_name = "rainfall" ; budgrain:units = "m/y" ; budgrain:FORTRAN_format = "e13.5" ; float budgmelt(time, y1, x1) ; budgmelt:long_name = "surface melt" ; budgmelt:units = "m/y" ; budgmelt:FORTRAN_format = "e13.5" ; float baseperc(time, y1, x1) ; baseperc:long_name = "percolation to base" ; baseperc:units = "m/y" ; baseperc:FORTRAN_format = "e13.5" ; float basefrml(time, y1, x1) ; basefrml:long_name = "basal freezing rate" ; basefrml:units = "m/y" ; basefrml:FORTRAN_format = "e13.5" ; float oceanmelt(time, y1, x1) ; oceanmelt:long_name = "sub-ice oceanic melt" ; oceanmelt:units = "m/y" ; oceanmelt:FORTRAN_format = "e13.5" ; float facemelt(time, y1, x1) ; facemelt:long_name = "face melt rate" ; facemelt:units = "m/y" ; facemelt:FORTRAN_format = "e13.5" ; float calvice(time, y1, x1) ; calvice:long_name = "calved ice" ; calvice:units = "m" ; calvice:FORTRAN_format = "e13.5" ; float maskwater(time, y1, x1) ; maskwater:long_name = "0=gd.ice/land, 1=fl.ice/ocean" ; maskwater:units = "0/1" ; maskwater:FORTRAN_format = "e13.5" ; float logcrhmel(time, y1, x1) ; logcrhmel:long_name = "basal sliding coefficient" ; logcrhmel:units = "m/y/Pa^2" ; logcrhmel:FORTRAN_format = "e13.5" ; float enhanceinv(time, y1, x1) ; enhanceinv:long_name = "extra enhancement (inv) factor for sheet flow" ; enhanceinv:units = " " ; enhanceinv:FORTRAN_format = "e13.5" ; float ts(time, y1, x1) ; ts:long_name = "surface temperature" ; ts:units = "C" ; ts:FORTRAN_format = "e13.5" ; float tb(time, y1, x1) ; tb:long_name = "basal temperature" ; tb:units = "C" ; tb:FORTRAN_format = "e13.5" ; float tbhomol(time, y1, x1) ; tbhomol:long_name = "basal homologous temperature" ; tbhomol:units = "C" ; tbhomol:FORTRAN_format = "e13.5" ; float frozfac(time, y1, x1) ; frozfac:long_name = "basal frozen fraction" ; frozfac:units = "0-1" ; frozfac:FORTRAN_format = "e13.5" ; float was(time, y1, x1) ; was:long_name = "surface ice z-velocity" ; was:units = "m/y" ; was:FORTRAN_format = "e13.5" ; float wab(time, y1, x1) ; wab:long_name = "basal ice z-velocity" ; wab:units = "m/y" ; wab:FORTRAN_format = "e13.5" ; float fluxsch(time, y1, x1) ; fluxsch:long_name = "grounding-line flux" ; fluxsch:units = "m2/y" ; fluxsch:FORTRAN_format = "e13.5" ; float utop(time, y1, x0) ; utop:long_name = "surface ice x-velocity" ; utop:units = "m/y" ; utop:FORTRAN_format = "e13.5" ; float ubot(time, y1, x0) ; ubot:long_name = "basal ice x-velocity" ; ubot:units = "m/y" ; ubot:FORTRAN_format = "e13.5" ; float ua(time, y1, x0) ; ua:long_name = "average ice x-velocity" ; ua:units = "m/y" ; ua:FORTRAN_format = "e13.5" ; float vtop(time, y0, x1) ; vtop:long_name = "surface ice y-velocity" ; vtop:units = "m/y" ; vtop:FORTRAN_format = "e13.5" ; float vbot(time, y0, x1) ; vbot:long_name = "basal ice y-velocity" ; vbot:units = "m/y" ; vbot:FORTRAN_format = "e13.5" ; float va(time, y0, x1) ; va:long_name = "average ice y-velocity" ; va:units = "m/y" ; va:FORTRAN_format = "e13.5" ; float msector(time, y1, x1) ; msector:long_name = "OH basin sector number" ; msector:units = "integer" ; msector:FORTRAN_format = "e13.5" ;