University of Toronto  |   Physics Department  |   Atmospheric Physics

Datasets

Paleo-topography data

ICE-6G --
Users of the data sets that define the ICE-6G(VM5a) model and that have been produced by employing it to make predictions of geodetically and geologically observable signals in the Earth system are requested to reference the following publications in which this model was originally presented:

Argus, D.F., Peltier, W.R., Drummond, R. and Moore, A.W.(2014) The Antarctica component of postglacial rebound model ICE-6G_C (VM5a) based upon GPS positioning, exposure age dating of ice thicknesses, and relative sea level histories. Geophys. J. Int., 198(1), 537-563, doi:10.1093/gji/ggu140.

Peltier, W.R., Argus, D.F. and Drummond, R. (2015) Space geodesy constrains ice-age terminal deglaciation: The global ICE-6G_C (VM5a) model.
J. Geophys. Res. Solid Earth, 120, 450-487, doi:10.1002/2014JB011176.
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Files are available for the following times (Ka)
26.0, 25.0, 24.0, 23.0, 22.0, 21.0,
20.5, 20.0, 19.5, 19.0, 18.5, 18.0, 17.5, 17.0, 16.5, 16.0,
15.5, 15.0, 14.5, 14.0, 13.5, 13.0, 12.5, 12.0, 11.5, 11.0,
10.5, 10.0, _9.5, _9.0, _8.5, _8.0, _7.5, _7.0, _6.5, _6.0,
_5.5, _5.0, _4.5, _4.0, _3.5, _3.0, _2.5, _2.0, _1.5, _1.0, _0.5, _0.0

Each file contains information for points on a 1x1 degree global grid.
The model's ice thickness field is given by the variable stgit.
Predictions obtained from the model are: topography (Topo), topography difference from present (Topo_Diff), Surface altitude (orog) and the land area fraction (sftlf) and ice area fraction (stgif).
Topography includes bathymetry and for an ice-shelf, orog will give the ice surface whereas Topo will give the ocean depth.
A file containing the ice-thickness for all times from 122Ka to the present is IceThick.nc.gz. This is again on a 1x1 degree grid (lower resolution than used in the calculation of predicted quantities). This ice-loading needs to be processed by the Sea Level Equation (SLE) solver in order to determine the history of grounded ice variation and paleo-topography through the most recent glacial cycle. In order to ensure accuracy in Antarctica, this input should be processed using the BEDMAP2 data set for modern bathymetry south of 60 degrees south latitude."

NETCDF FILES:
The above predictions are in netcdf files. Free software is available to read files of this kind. eg Panoply from http://www.giss.nasa.gov/tools/panoply/ available for Windows/Mac/Linux. (My experience is limited to Windows). This allows you to plot the fields or export them into text or csv files.
Older tools often used on Unix machines are ncdump and ncview.
ncdump is part of the netcdf package available from https://www.unidata.ucar.edu/downloads/netcdf but may also be available "stand-alone"
NCL (http://www.ncl.ucar.edu/Download) is a free graphics package well-suited to making plots directly from data in netcdf files.

Other predictions:
Many of the following are calculated at order 512 which is higher resolution than the results in the published papers. This is indicated when the filename contains O512. The ICE-6G_C deglaciation history and the earth model with VM5a viscosity profile are identical to those in the two publications. There are (usually minor) differences between these results and those obtained at order 256 as published in the Journals. Differences are greatest where the higher resolution is significant, such as the Antarctic Peninsula where the area of land and ice is relatively narrow.

Rate of change of sea-level on a 1x1 grid: dsea.1grid.nc
Rate of change of sea-level on a 0.2x0.2 grid: dsea.12mgrid.nc
Rate of radial displacement (UP) on a 1x1 grid: drad.1grid.nc
Rate of radial displacement (UP) on a 0.2x0.2 grid: drad.12mgrid.nc
Horizontal Velocity (East & North) on a 1x1 grid: Hvel.1grid.nc
Horizontal Velocity (East & North) on a 0.2x0.2 grid: Hvel.12mgrid.nc

Rate of change of sea level at PSMSL locations: drsl.PSMSL.txt
Rate of radial displacement (UP) at PSMSL locations: drad.PSMSL.txt
Velocities (East, North, UP) at Geodetic Sites: GS_vels.txt

Stokes trend coefficients: The original file of coefficients posted on the JGR website as supplementary material to Peltier et al 2015 is Stokes_trend_O256_orig.txt.gz
Stokes coefficients obtained with a higher resolution calculation are
ICE-6G_High_Res_Stokes_trend.gz
Alternative results are given by Stokes_trend_O256_reducedcode.txt.gz
This set of Stokes coefficients differ from that originally posted as supplementary material on the JGR web site to accompany Peltier et al (2015) in that it has been computed using a version of the code from which a number of physically important processes have been eliminated. These processes involve a detailed description of grounding line migration, processes which are especially important around the perimeter of the Antarctic ice sheet. The version of the solver with full physics, as recently described in Stuhne and Peltier (2015), is critical for inferring the amount of grounded ice that could have been eliminated from the southern continent at Meltwater Pulse 1A time as inferred in Argus et al (2014). More important for the full physics version of the code is the elimination of grounded ice at Meltwater Pulse 1B time which occurs primarily from the Weddell Sea and Ross Sea embayments. The reduced version of the code that does not include grounding line migration cannot properly explain the evolution of land ice that is grounded below sea level, a phenomenon that is critical to the description of the contribution of Antarctica to MWP 1B in the ICE6G_C (VM5a) model. The full physics version of the code must be run at higher than (degree and order 256) resolution to accurately represent the Stokes coefficients for application to the southern continent.
NOTE: the previously posted comments concerning the file of alternatve Stokes coefficients provided here were misleading in suggesting that the original coefficients made available on the JGR web site were incorect in some way. The only flaw in this set is that it has turned out that the resolution emloyed in model construction, which truncated the basis of spherical harmonics employed to (degree and order 256), was insufficient to accurately represent the physically important process of grounding line migration. This led to the aliasing of power at short wavelengths in the Stokes spectrum to longer wavelengths (smaller spherical harmonic degree).
(When the calculation is run at higher resolution, the icesheet remains the same but is sampled at a denser grid of points.)

Stuhne G.R., Peltier, W.R. (2015)
Reconciling the ICE-6G_C reconstruction of glacial chronology with ice sheet dynamics: The cases of Greenland and Antarctica.
J. Geophys. Res. Earth Surf. 120, 1-25, doi:10.1002/2015JF003580.
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ICE-5G --
NetCDF files for ICE-5G (VM2 L90) model version 1.2. The underlying present-day topography is ETOPO2 instead of Terrainbase. Files are available archived with tar and gzip or zip (size is given before compression). Each file contains data on Surface Altitude, Thickness of the Ice Sheet, and the Ice-mask. The values are point-values at the associated grid-point. The Ice-mask is either 100 if there is ice at that point, or zero if there is no ice. The following data files are available:

.zip, .gz: 0 KBP, 10 min resolution (27 Mb)
.zip, .gz: 21 KBP, 10 min resolution (27 Mb)
.zip, .gz: 0 KBP, 1 deg resolution (773 Kb)
.zip, .gz: 21 KBP, 1 deg resolution (773 Kb)
.zip, .tar.gz: 0-21 KBP inclusive, 1 deg resolution (39 files, 30 Mb)

Users of the data sets that define the ICE-5G(VM2) model and that have been produced by employing it to make predictions of geodetically and geologically observable signals in the Earth system are requested to reference the following publication in which this model was originally presented:
W.R. Peltier, 2004. Global Glacial Isostasy and the Surface of the Ice-Age Earth: The ICE-5G (VM2) Model and GRACE, Ann. Rev. Earth and Planet. Sci., 32, 111-149.
Follow this link to get the full text of the paper in PDF format.

Ice thickness information that was previously available from the SBL website is available: 26-0Ka, 122-27Ka: This is given for points on an order 256 Gaussian grid. [Note that ICE-5G does not have realistic ice-margins prior to LGM]

Prior publications describing the detailed analysis which has led to the modifications of the ice-sheet topography in the individual geographic regions are as follows:

The British Isles -- W.R. Peltier, Ian Shennan, Rosemarie Drummond and Ben Horton, On the Postglacial Isostatic adjustment of the British Isles and the Shallow Viscoelastic Structure of the Earth, Geophys. J. Int., 148, 443-475, 2002

Greenland -- Lev Tarasov and W.R. Peltier, Greenland Glacial History and Local Geodynamic Consequences, Geophys. J. Int., 150, 198-229, 2002

North America -- W.R. Peltier, Global Glacial Isostatic Adjustment: Paleogeodetic and Space-Geodetic Tests of the ICE-4G (VM2) Model, J. Quat. Sci., 17, 491-510, 2002

Northwestern Europe/Eurasia -- The new results for this region are described for the first time in Peltier (2004) and rely in large part on the ice-margins obtained in the QUEEN project sponsored by the European Science Foundation.

Users of the ICE-5G data sets whose focus is upon a particular geographic region are requested to reference the most relevant of the above regionally focussed analyses as well as the Peltier (2004) publication.

Predictions of the rate of RSL rise due to GIA effect at PSMSL locations

Predictions for ICE-5G (VM2 L90) model (version 1.3) for PSMSL tidegauge sites (in ASCII format). (Note: version 1.3f was here for a short time in error. It is an experimental version, not a fixed one.)

The files were updated Aug 13,2012 using the latest PSMSL station list- no change has been made to ICE-5G since March 2012.

Files contain values of the rates of relative sealevel rise and of vertical motion of the solid earth in mm/yr Each shows the coordinates of PSMSL stations followed by 3 columns showing rates-of-change:

(1) a value using the predicted difference in rsl for the last 250yrs
(2) a value using the predicted difference in rsl for the coming 250yrs
(3) a value centred on "now" using the predicted rsl at now +/- 250yrs

Obviously (3) is the average of (1) and (2) and we suggest you use this number. The other two can give some idea of how smooth the predicted variation is (but is definitely not to be called an error-bar!)

AN ERROR WAS DISCOVERED IN March 2012 AND THE FILES HAVE BEEN REPLACED WITH CORRECTED VERSIONS.

There are 4 netcdf files giving values (also corrected) on a 1x1 degree grid:
rate of sealevel rise
rate of vertical motion
rate of change of geoid
horizontal velocity components

Details of the earth model VM2_L90

Users of the data sets that define the ICE-5G(VM2) model and that have been produced by employing it to make predictions of geodetically and geologically observable signals in the Earth system are requested to reference the following publication in which this model was originally presented:
W.R. Peltier, 2004. Global Glacial Isostasy and the Surface of the Ice-Age Earth: The ICE-5G (VM2) Model and GRACE, Ann. Rev. Earth and Planet. Sci., 32, 111-149.
Follow this link to get the full text of the paper in PDF format.