Documentation for PISM, the Parallel Ice Sheet Model

NEWS: PISM version 1.0 is out!

PISM v1.0

olympics-crop.jpg

Modeled ice flow speed on the Olympic Peninsula, Washington state, USA, for conditions near the LGM.

The Parallel Ice Sheet Model PISM v1.0 is open source and capable of high resolution. It has been widely adopted as a tool for doing science since 2011.

Features include:

Application of the Month

November 2017

Glaciologists know little about the conditions at the beds of glaciers because these places are so hard to observe directly. Nonetheless most PISM runs need and use a model of the basal conditions. This includes a model of the basal topography, derived from ice-penetrating radar (though necessarily more than the “raw” reflections), and a model of the relation between basal sliding velocity and shear stress (e.g. a power law with uncertain parameters).

Inverse modeling can examine the relationship between available surface observations and the conditions at the base. This paper assesses the intermediate quantities in an inverse modeling exercise. Such a calculation generates a (forward) model result for which a norm of the difference between the observations and the model result is minimized in some sense. This difference itself, the residual, contains information which is lost in computing its norm. These authors examine the residual, and other quantities as well, for meaning. There are several types of errors in glaciological inverse modeling which generates basal shear stress. These include observation errors (in the surface elevation and velocity), geometry errors, ice temperature errors, and “model errors”. The last are particularly interesting in the PISM context; a question addressed by this paper is “what are the manifestations of the simplifications in PISM in the sense of residual features?” A particular focus is on the difference between upstream and near-terminus regions of a deep-trough outlet glacier in the Greenland ice sheet.

2017/11/16 14:48 · Ed Bueler

Latest News

Openhub's summary of the PISM project

We think PISM has pretty-good open-source-software habits. But don't take our word for it. Here is the automatically-generated nutshell (here, on 4 November 2017) at openhub.net:

In a Nutshell, Parallel Ice Sheet Model (PISM)…

  • has had 6,867 commits made by 21 contributors representing 76,716 lines of code
  • is mostly written in C++ , with a well-commented source code
  • has a well established, mature codebase, maintained by a large development team, with stable Y-O-Y [year-on-year] commits
  • took an estimated 19 years of effort (COCOMO model), starting with its first commit in September, 2006, ending with its most recent commit 2 days ago
2017/11/04 23:28 · Ed Bueler

PISM v1.0 is out

This release has substantial changes to the code base, but users will not see many large differences. The goal of most code changes was to improve modularity and usability, making PISM easier to use, maintain and extend.

User-visible changes include the following.

  • New mass transport code makes it easier to “balance the books”.
  • PISM's grids are no longer transposed (y,x versus x,y).
  • Adds an optimized implementation of the GPBLD flow law for the Glen n=3 case.
  • Adds von Mises calving.
  • Adds more diagnostic quantities (127 spatially-variable fields and 38 scalar variables in total).
  • Better code, better documentation, more regression and verification tests.

For a more complete list of changes since v0.7, please see CHANGES.rst in the source release.

If you already have a Git repository for PISM then upgrade by doing

git fetch origin
git checkout master

in the PISM source tree. (Or get a new tagged .tar.gz or .zip at github.com/pism/pism/releases.) Then run

make install

in the build directory.

Please see the Installation Manual for detailed instructions.

Help with installation and usage is available through uaf-pism@alaska.edu.

2017/10/19 18:16 · Constantine Khroulev

The blog for HPC provider Mellanox Technologies, which supplies fast interconnects for many supercomputers, features Andy Aschwanden's work using PISM for studying the Greenland Ice Sheet.

2017/08/29 09:50 · Ed Bueler

Team

PISM is jointly developed at the University of Alaska, Fairbanks (UAF) and the Potsdam Institute for Climate Impact Research (PIK). For more about the team see the UAF Developers and PIK Developers pages.

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, NNX16AQ40G, NNX17AG65G) and by NSF grants PLR-1603799 and PLR-1644277.

home.txt · Last modified: 2017/11/15 10:36 by Ed Bueler
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