etopo1_iceΒΆ

This program generates a global map of ice extent and elevation on a 1-minute grid. It uses the following ModelE input files, found bin searching the colon-separated path in the MODELE_FILE_PATH environment variable.

  1. ZETOPO1.NCEI-SeparateGreenland.nc (1-minute): Extent of ice sheet, plus elevation, on global 1-minute grid. This is a modified version of the standard ModelE input files ZETOPO1.NCEI, in which FOCEAN (fractional ocean cover) is set to 1 for ocean grid cells, 0 for continent, an 2 for Greenland. This convention allows etopo1_ice to remove Greenland from its output, if needed, for two-way coupled runs where a modeled Greenland will be used in its place.
  2. ZNGDC1 (1-degree): Ice sheet fractions in northern hemisphere.

etopo_ice takes a singe argument, naming its output file (without the .nc extension). The -g flag may also be used to include Greenland in the output; otherwise, the Greenland island and ice sheet are removed, so a model-based Greenland may be used instead (for two-way coupling).

For example, etopo1_ice -g etopo1_ice_g produces the files etopo1_ice_g1m.nc, which contains global ice extent and elevation at 1-minute resolution:

netcdf etopo1_ice_g1m {
dimensions:
        jm1m = 10800 ;
        im1m = 21600 ;
variables:
        short ZICETOP1m(jm1m, im1m) ;
                ZICETOP1m:units = "m" ;
                ZICETOP1m:source = "ETOPO1" ;
        short ZSOLG1m(jm1m, im1m) ;
                ZSOLG1m:units = "m" ;
                ZSOLG1m:source = "ETOPO1" ;
        short FOCEAN1m(jm1m, im1m) ;
                FOCEAN1m:units = "m" ;
                FOCEAN1m:source = "ETOPO1" ;
        short FGICE1m(jm1m, im1m) ;
                FGICE1m:description = "Fractional ice cover (0 or 1)" ;
                FGICE1m:units = "1" ;
                FGICE1m:source = "etopo1_ice.cpp output" ;

// global attributes:
                :source = "etopo1_ice.cpp" ;
}

Variables are as follows:

  • ZICETOP: Elevation of top of the ice
  • ZSOLG: Elevation of the ground. Ice thickness is ZICETOP-ZSOLG. For areas not covered by ice, ZICETOP==ZSOLG.
  • FOCEAN: Fraction of grid cell covered in ocean. Will be 0 or 1 for 1-minute file.
  • FGCIE: Fraction of grid cell covered in ice. Will be 0 or 1 for 1-minute file.

It also produces the file etopo1_ice_gh.nc, which contains the same data, averaged to 1/2-degree resolution. This file is easier to plot or otherwise visualize.