Computing ice age

By default, PISM does not compute the age of the ice because it does not directly impact ice flow when using the default flow laws. It is very easy to turn on. Just set -age. A 3D variable age will appear in output files. It is read at input if -age is set and otherwise it is ignored even if present in the input file. If -age is set and the variable age is absent in the input file then the initial age is set to zero.

The age of the ice can be used in two parameterizations in the SIA stress balance model:

  1. Ice grain size parameterization based on data from [62] and [63] (Vostok core data). In PISM, only the Goldsby-Kohlstedt flow law (see Ice rheology) uses the grain size.
  2. The flow enhancement factor can be coupled to the age of the ice as in [64]: during Eemian and Holocene \(e\) is set to
    • stress_balance.sia.enhancement_factor_interglacial during Eemian and Holocene,
    • stress_balance.sia.enhancement_factor otherwise.

See time.eemian_start, time.eemian_end, and time.holocene_start.

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