Documentation for PISM, a parallel Ice Sheet Model

NEWS: PISM's new mass conserving subglacial hydrology models.

The Parallel Ice Sheet Model pism0.6 is an open source, parallel, high-resolution ice sheet model. Features:

  • hierarchy of available stress balances
  • marine ice sheet physics, dynamic calving fronts
  • polythermal, enthalpy-based conservation of energy scheme
  • subglacial hydrology and till model
  • extensible coupling to atmospheric and ocean models
  • inversion toolbox in Python
  • verification and validation tools
  • complete documentation for users and developers
  • uses MPI and PETSc for parallel simulations
  • reads and writes CF-compliant NetCDF

PISM Application of the Month

August 2014

Click the image to go to The Cryosphere journal page.

Changing basal conditions during the speed-up of Jakobshavn Isbræ, Greenland
investigators: M. Habermann, M. Truffer, and D. Maxwell
journal: The Cryosphere

We use a Tikhonov inverse method, with PISM's SSA as a forward model, to invert for basal conditions from surface velocity data throughout a well-observed period (1985, 2000, 2005, 2006 and 2008) of rapid change. Ice-softness, model norm, and regularization parameter choices are justified using the data-model misfit metric and the L-curve method. The sensitivity of the inversion results to these parameter choices is explored. We find a lowering of effective basal yield stress in the first 7 km upstream from the 2008 grounding line and no significant changes higher upstream. The temporal evolution in the fast flow area is in broad agreement with a Mohr–Coulomb parameterization of basal shear stress, but with a till friction angle much lower than has been measured for till samples. The lowering of effective basal yield stress is significant within the uncertainties of the inversion, but it cannot be ruled out that there are other significant contributors to the acceleration of the glacier.

2014/08/04 18:31 · Ed Bueler

Latest News

PISM 0.6.1 has bug fixes

Only fixes and improvements that should not break existing functionality are included in this release. We recommend updating from v0.6 unless you have a good reason against it. Upgrade by doing “git pull” in the PISM source tree. (Or get a new tagged ”.tar.gz” or ”.zip” at github.com/pism/pism/releases.) Then do “make install” in the build directory.

For a full list of changes since v0.6, please see https://github.com/pism/pism/blob/stable0.6/CHANGES.md

Send email to help@pism-docs.org for help with any version of PISM.

2014/05/31 16:48 · Ed Bueler

Ice plug prevents irreversible discharge from East Antarctica

In a just-published Nature Climate Change article, Potsdam Institute for Climate Impact Research authors Matthias Mengel and Anders Levermann use PISM to define the “ice-plug” which, if removed from the coastal ice in the Wilkes Basin of East Antarctica, would initiate irreversible retreat of the grounded ice in that basin. The modeled retreats, which occur on a time scale of a few thousand years, generate 3–4 m of sea level rise from the region surrounding the basin. Thus this basin is a potential “tipping-point” ice sheet configuration, in additional to the better-known West Antarctica configurations.

For the PISM user this paper is an indication of its ability to model an ice sheet region (hashed in figure) at high resolution across a range of ice dynamics parameters and climate forcing choices.

2014/05/05 11:35 · Ed Bueler

PISM team

PISM is jointly developed at the University of Alaska, Fairbanks (UAF) and the Potsdam Institute for Climate Impact Research (PIK). UAF developers, who are in the Glaciers Group at the GI, are supported by NASA's Modeling, Analysis, and Prediction and Cryospheric Sciences Programs (grants NAG5-11371, NNX09AJ38C, NNX13AM16G, NNX13AK27G) and by the Arctic Region Supercomputing Center.

home.txt · Last modified: 2014/08/03 09:02 by Ed Bueler
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