[MASK]: NORCE-CISM

[hgoelzer]

Overview

• Product name and version: CISM model output
• Purpose of your product: Ice sheet evolution and projections
• Geographic region: Greenland and Antarctica
• Year(s) covered by product: 1950-2300

Upstream

• What upstream mask product did you use?
  The ice sheet mask is set at init, typically inherited from either the SMB forcing product (MAR, RACMO, ...) or from a geometric input dataset (BedMachine).
  The ice sheet mask is often first held constant during spinup, but typically released for a projection.

• Reason for using this mask
  Matching the SMB product is practical and allows to constrain the ice sheet model to the 'observed' mask.

• If you modified the upstream mask, for example, to define and split ‘main’ vs. ‘peripheral’, how and why?
  Masking out the connected periphery can be awkward dynamically. Removing disconnected ice caps and glaciers is more obvious. The reason to do that would be that the ice sheet model is not very good simulating those smaller glaciers.

• Effort required by you if upstream product changed (to a community standard)
  No problem if ahead of time. But initialisation and spinup are the most expensive. So better to change once.

• If you used internal basins, which product and why?
  We used internal basins diagnostically, following ISMIP6. They used both IMBIE basin sets (Rignot and Zwally).

• If you subset to a geographical region (Greenland, Antarctica, sub-region, peripheral, individual glacier), how and why
  So far only simulated entire ice sheets Greenland and Antarctica.

• Type: raster

• Resolution if raster: 32x32km, 16x16km, 8x8km, 4x4km, 2x2km, 1x1km (GrIS)

• Projection information: EPSG 3031, EPSG 3413

• Year or years of input product(s): Same as observational datasets, typically early 2000

Internal

Internal ice sheet mask is the result of a dynamic ice flow simulation. Unless a fixed mask is imposed, the ice sheet produces it's own mask.

• All masks have boundaries. How, and why did you define yours?
  Operating on a computationally feasible domain, or trying to match the diagnostic grid (ISMIP6/7).
  For GrIS, often masking out Ellesmere Island, Iceland and other land outside of Greenland.

• If your product includes distinction between main and peripheral ice sheet, how did you define this? If possible, cite source, equation, pseudo-code, or text description)
  CISM has an option to detect disconnected ice and remove it. This is a search algorithm from a known internal divide location. Not applied by default.
  CISM can apply an imposed and changing ice mask at runtime. This comes with the ISMIP6 forcing implementation.
  Can remove overlapping glaciers in post-processing, based on RGI.

• Effort required if your internal product changed (to a community standard)
  No effort.

• If you used internal basins, how did you define them, or which product and why?
  We used internal basins diagnostically, following ISMIP6. They used both IMBIE basin sets (Rignot and Zwally).

• Geographical region (Greenland, Antarctica, sub-region, peripheral, individual glacier)
  So far only simulated entire ice sheets Greenland and Antarctica.

• Type: raster

• Resolution if raster: adjusted to upstream

• Projection information: EPSG 3031, EPSG 3413

Downstream

Ice sheet model diagnostic output.
Typically interpolated from the native model grid to match a target diagnostic grid (ISMIP6/7, PROTECT) at a given resolution.
Even if the native grid is regular and at the same resolution, it could be offset in x/y to the diagnostic grid

Other notes