Replacing value of minthck_ice_sheet in glissade_masks.F90

[mpetrini-norce]

minthck_ice_sheet is the thickness threshold (in meters) under which new ice sheet cells will not be initialized. A value of 2000 meters was originally selected to prevent the formation of ice caps in northern Greenland during the CESM2/CISM2 coupled spinup (https://doi.org/10.1029/2019MS001984). However, in the coupled 1pctCO2 simulation this value led to massive chunks of ice to be immediately discharged to the ocean as soon they would disconnect from the ice sheet. This resulted in unrealistic, very high spikes in the calving rate. To avoid this, a SourceMods change was introduced setting this constant to a safe value of 100 meters. To avoid the use of SourceMods, I suggest that this value (100 m) should be the standard value (at least for the CISM version included in NorESM2.5_alpha05 and subsequent releases.

CISM/libglissade/glissade_masks.F90

Line 628 in 3eeda3e

minthck_ice_sheet = 2000.d0 !> thickness threshold (m) for initializing ice sheet cells

@hgoelzer @mvertens