tage.rst - pism - [fork] customized build of PISM, the parallel ice sheet model (tillflux branch)
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       tage.rst (1246B)
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            1 .. include:: ../../../global.txt
            2 
            3 .. _sec-age:
            4 
            5 Computing ice age
            6 -----------------
            7 
            8 By default, PISM does not compute the age of the ice because it does not directly impact
            9 ice flow when using the default flow laws. It is very easy to turn on. Just set
           10 :opt:`-age`. A 3D variable ``age`` will appear in output files. It is read at input if
           11 ``-age`` is set and otherwise it is ignored even if present in the input file. If ``-age``
           12 is set and the variable ``age`` is absent in the input file then the initial age is set to
           13 zero.
           14 
           15 The age of the ice can be used in two parameterizations in the SIA stress balance model:
           16 
           17 #. Ice grain size parameterization based on data from :cite:`DeLaChapelleEtAl98` and
           18    :cite:`LipenkovEtAl89` (Vostok core data). In PISM, only the Goldsby-Kohlstedt flow law
           19    (see :ref:`sec-rheology`) uses the grain size.
           20 
           21 #. The flow enhancement factor can be coupled to the age of the ice as in
           22    :cite:`Greve97Greenland`: during Eemian and Holocene `e` is set to
           23 
           24    - :config:`stress_balance.sia.enhancement_factor_interglacial` during Eemian and Holocene,
           25    - :config:`stress_balance.sia.enhancement_factor` otherwise.
           26 
           27 See :config:`time.eemian_start`, :config:`time.eemian_end`, and
           28 :config:`time.holocene_start`.