PISM User’s Manual

Welcome! All information about PISM is online at the home page

https://www.pism.io

Please see the extensive lists of PISM publications and applications at that page.

This User’s Manual gives examples of how to run PISM using publicly-available data for: the whole Greenland ice sheet, the Jakobshavn outlet glacier in Greenland, the Ross ice shelf in Antarctica, and a number of simplified geometry tests. It documents all the PISM’s command-line options and configuration parameters. It summarizes the continuum models used by PISM, and it illustrates how PISM’s numerical approximations are verified.

See the Installation Manual for how to download the PISM source code and install it, along with needed libraries. The Climate Forcing Manual extends this Manual to cover additional couplings to atmosphere and ocean models and data.

Users who want to understand more deeply how PISM is designed, or who want to extend it, will need to go beyond what is described here. See the Source Code Browser, which is online for the latest stable version. It can be generated from source code as described in Rebuilding PISM documentation. It gives a complete view of the class/object structure of the PISM source code.

Warning

PISM is an ongoing research project. Ice sheet modeling requires many choices. Please don’t trust the results of PISM or any other ice sheet model without a fair amount of exploration. Also, please don’t expect all your questions to be answered here. Write to us with questions or join the PISM workspace on Slack.

Contents

• Getting started: a Greenland ice sheet example
  • Input data
  • First run
  • Watching the first run
  • Second run: a better ice-dynamics model
  • Third run: higher resolution
  • Fourth run: paleo-climate model spin-up
  • Grid sequencing
  • An ice dynamics parameter study
• Ice dynamics, the PISM view
  • Stress balance models: SIA, SSA, and the First Order Approximation
  • A hierarchy of simplifying assumptions for grounded ice flow
  • Evolutionary versus diagnostic modeling
  • Climate inputs, and their interface with ice dynamics
• Initialization and bootstrapping
  • Initialization from a saved model state
    • -i file format
  • Bootstrapping
    • -bootstrap file format
• Modeling choices
  • Model domain, grid, and time
    • Computational box
    • Spatial grid
      • Grid registration
      • Grid projections
      • Parallel domain distribution
    • Model time
      • Calendars
      • Re-starting an interrupted run using -time_file
      • Diagnostic computations
  • Ice dynamics and thermodynamics
    • Choosing the stress balance
      • Shallow shelf approximation (SSA)
        • Parameters
        • Technical remarks
      • Shallow ice approximation (SIA)
        • Surface gradient method
        • Parameterization of bed roughness
        • Coupling to the age of the ice
        • Parameters
      • Weertman-style sliding law
        • Parameters
      • Blatter’s model
        • Surface gradient computation
        • Adaptive time stepping
        • Practical preconditioners choices
        • Parameters
    • Ice rheology
      • Flow law choices
      • Enhancement factor and exponent
    • Modeling conservation of energy
    • Computing ice age
      • Isochronal layer tracing
  • The subglacier
    • Controlling basal strength
      • Choosing the sliding law
        • Lateral drag
      • Determining the yield stress
        • Till friction angle heuristic
        • Till friction angle optimization
      • Determining the effective pressure
        • Controlling minimum effective pressure
    • Subglacial hydrology
      • The default model: -hydrology null
        • “Steady state flow” model
      • The mass-conserving model: -hydrology routing
    • Earth deformation models
      • Point-wise isostasy
      • Lingle-Clark
      • Given bed deformation history
  • Marine ice sheet modeling
    • PIK options for marine ice sheets
      • Stress condition at calving fronts
      • Partially-filled cells at the boundaries of ice shelves
      • Iceberg removal
      • Sub-grid treatment of the grounding line position
    • Flotation criterion, mask, and sea level
    • Calving and front retreat
      • Overview
        • Scaling calving rates
      • Eigen calving
      • von Mises stress calving
      • Hayhurst calving
      • Calving of thin floating ice
      • Calving of all floating ice
      • Prescribed front retreat
    • Modeling melange back-pressure
    • Fracture density modeling
  • Modeling individual outlet glaciers
    • Energy
    • Stress balance
    • Mass continuity
      • Mass balance adjustment
      • Calving
  • Disabling sub-models
  • Dealing with more difficult modeling choices
• Practical usage
  • Handling NetCDF files
  • Input and output
    • PISM’s I/O performance
  • Understanding adaptive time-stepping
    • Parameters
  • Scalar diagnostic quantities
    • Parameters
    • Comments
  • Spatially-varying diagnostic quantities
    • Parameters
  • Snapshots of the model state
    • Parameters
  • Run-time diagnostic viewers
  • PISM’s configuration parameters and how to change them
    • Managing parameter studies
    • Saving PISM’s configuration for post-processing
  • Regridding
  • Signals, to control a running PISM model
  • Balancing the books
    • 2D diagnostics
    • Scalar diagnostics
    • Mass accounting in subglacial hydrology models
    • Mass accounting in the PDD model
    • Mass conservation and “rough” bed topography
  • PETSc options for PISM users
  • Utility and test scripts
  • Using PISM for flow-line modeling
  • Managing source code modifications
  • ISMIP6 Greenland
    • Top surface mass balance and temperature
    • Frontal melt parameterization
    • Parameterized front retreat
    • Output variables
• Simplified geometry experiments
  • EISMINT II
  • MISMIP
  • MISMIP3d
  • ISMIP-HOM
    • Experiments A, B, C, D
    • Experiment E
• Verification
  • Sample convergence plots
• Validation case studies
  • An SIA flow model for a table-top laboratory experiment
  • An SSA flow model for the Ross Ice Shelf in Antarctica
    • Preprocessing input data
    • Diagnostic computation of ice shelf velocity
    • Extending this example to other ice shelves
    • Prognostic modelling using eigencalving
• Example: A regional model of the Jakobshavn outlet glacier in Greenland
  • Get the drainage basin delineation tool
  • Preprocess the data and get the whole ice sheet model file
  • Identify the drainage basin for the modeled outlet glacier
  • Cut out the computational domain for the regional model
  • Quick start
  • Spinning-up the regional model on a 5 km grid
  • Century run on a 2 km grid
  • Plotting results
• Configuration parameters
• Diagnostic quantities
  • Spatially-variable fields
  • Scalar time-series

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