tindex.rst - pism - [fork] customized build of PISM, the parallel ice sheet model (tillflux branch)
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       tindex.rst (3843B)
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            1 .. include:: ../../global.txt
            2 
            3 .. _sec-simp:
            4 
            5 Simplified geometry experiments
            6 ===============================
            7 
            8 There have been three stages of ice sheet model intercomparisons based on simplified
            9 geometry experiments since the early 1990s :cite:`BuelerSpray`.
           10 
           11 EISMINT I (European Ice Sheet Modeling INiTiative) :cite:`EISMINT96`\ [#]_ was the first of
           12 these and involved only the isothermal shallow ice approximation (SIA). Both fixed margin
           13 and moving margin experiments were performed in EISMINT I, and various conclusions were
           14 drawn about the several numerical schemes used in the intercomparison. EISMINT I is
           15 superceded, however, by verification using the full variety of known exact solutions to
           16 the isothermal SIA :cite:`BLKCB`. The "rediscovery", since EISMINT I, of the Halfar similarity
           17 solution with zero accumulation :cite:`Halfar83`, and verification runs using that solution,
           18 already suffices to measure the isothermal SIA performance of PISM more precisely than
           19 would be allowed by comparison to EISMINT I results.
           20 
           21 EISMINT II :cite:`EISMINT00` pointed out interesting and surprising properties of the
           22 thermocoupled SIA. References :cite:`BBL`, :cite:`Hindmarsh04`, :cite:`Hindmarsh06`,
           23 :cite:`PayneBaldwin`, :cite:`SaitoEISMINT`, :cite:`BBssasliding` each interpret the
           24 EISMINT II experiments and/or describe attempts to add more complete physical models to
           25 "fix" the (perceived and real) shortfalls of ice sheet model behavior on EISMINT II
           26 experiments. We believe that the discussion in :cite:`PayneDongelmans`,
           27 :cite:`PayneBaldwin`, :cite:`BBL` adequately explains the "spokes" in EISMINT II
           28 experiment F as a genuine fluid instability, while :cite:`Fowler01` and Appendix B of
           29 :cite:`BBssasliding` adequately cautions against the continuum model that generates the
           30 "spokes" in EISMINT II experiment H. Thus we can move on from that era of controversy. In
           31 any case, PISM has built-in support for all of the published and unpublished EISMINT II
           32 experiments; these are described in the next subsection.
           33 
           34 The ISMIP (Ice Sheet Model Intercomparison Project) [#]_ round of intercomparisons covers
           35 2008--2013 (at least). There are four components of ISMIP substantially completed, namely
           36 HOM = Higher Order Models :cite:`ISMIPHOM`, :cite:`HOMelmer`, HEINO = Heinrich Event
           37 INtercOmparison :cite:`GreveTakahamaCalov`, :cite:`Calovetal2009HEINOfinal`, MISMIP
           38 (below), and MISMIP3d (also below).
           39 
           40 PISM participated in HEINO, but this ability is unmaintained. We believe the continuum
           41 problem described by HEINO, also used in EISMINT II experiment H (above), is not
           42 meaningfully approximate-able because of a required discontinuous jump in the basal
           43 velocity field. The continuum problem predicts infinite vertical velocity because of this
           44 jump (:cite:`BBssasliding`, Appendix B). Details of the numerical schemes and their results are
           45 irrelevant if the continuum model makes such a prediction. PISM offers the physical
           46 continuum model described in :cite:`BBssasliding`, an SIA+SSA hybrid, as an alternative to the
           47 continuum model used in ISMIP-HEINO and EISMINT II experiment H. Indeed the SIA+SSA hybrid
           48 is offered as a unified shallow model for real ice sheets (section :ref:`sec-dynamics`).
           49 
           50 There is no current plan to support ISMIP-HOM :cite:`ISMIPHOM`, :cite:`HOMelmer`, but
           51 comparison of shallow PISM results to exact Stokes solutions is a goal for PISM
           52 evaluation.
           53 
           54 A third and fourth ISMIP parts are the two parts of the Marine Ice Sheet Model
           55 Intercomparison Project, MISMIP :cite:`MISMIP2012` and MISMIP3D :cite:`MISMIP3d2013`. These
           56 experiments are supported in PISM, as described in subsections :ref:`sec-MISMIP` and
           57 :ref:`sec-MISMIP3d` below.
           58 
           59 .. toctree::
           60    :caption: Intercomparison projects
           61 
           62    eismint-2.rst
           63 
           64    mismip.rst
           65 
           66    mismip3d.rst
           67 
           68 .. rubric:: Footnotes
           69 
           70 .. [#] See |eismint-url|
           71 
           72 .. [#] See |ismip-url|