Calculate sea ice extent area from sea ice thickness data

[Ming Yang <myang@xxxxxxxxxxxxx>]

Hi, folks
   I have a netcdf file which contains a variable HIC describing the
global sea ice thickness. I am thinking to calculate the corresponding sea
ice extent area from this variable by ferret. My algorithm is like this.
Whenever the sea ice thickness at certain point is greater than certain
value (for example, 0.1m), I assume the whole area represented by this
point is covered by sea ice. Then I sum up all of them to get global sea
ice extent area. Do you guys know how to do this in ferret? Thank you for
your help.


Ming