Documentation for PISM, the Parallel Ice Sheet Model

NEWS: PISM version 1.0 is out!

PISM v1.0


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

October 2017

When thermodynamics are coupled to basal sliding through the production of liquid water in a modeled basal till layer, PISM may exhibit cyclic, surge-like behavior. This paper studies such ice-discharge instabilities in PISM for a buttressed ice-sheet-stream-shelf system. When present the simulated surge cycles, which are believed to be fundamentally physical, have 1000 to 5000 year periods in the studied parameter ranges. This work extends prior work on cyclic PISM behavior (Bueler & Brown 2009, van Pelt & Oerlemans 2012) to marine ice sheet conditions, but the 1 km resolution model here is significantly more complete than in those studies. It includes stable0.7 version implementations of enthalpy-based thermodynamics, an improved till-layer hydrology model (Bueler & van Pelt 2015), a sub-grid scheme at the grounding line (Feldman et al 2014), and a buttressed ice shelf. The surface conditions are all constant, independent even of surface elevation, so the cyclic behavior arises purely internally in the ice and the basal layer. This paper includes a new and careful analysis of cyclic behavior, identifying three competing time-scales controlling such cycles. Results suggest that ice sheets of medium thickness may be more susceptible to surging than thin or thick ones. The mechanisms studied here may play a role in Heinrich events of the late-LGM Laurentide Ice Sheet and/or in ice-stream shutdown and reactivation observed in West Antarctica. This is the definitive study of the PISM parameter space for modeled ice stream-shelf systems.

2017/10/17 19:28 · Ed Bueler

Latest News

Openhub's summary of the PISM project

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

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 Then run

make install

in the build directory.

Please see the Installation Manual for detailed instructions.

Help with installation and usage is available through

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

EGU Early Career Award for PISM-author Ricarda Winkelmann

Congratulations to Ricarda Winkelmann of the University of Potsdam for receiving the EGU's Outstanding Early Career Scientists Award in Cryospheric Sciences. Her involvement with ice sheet modeling started with a very cold trip to Fairbanks Alaska in November 2008, leading to a 2011 paper on the design of PISM-PIK which is one of the most-cited PISM papers. (PISM-PIK introduced new features for marine ice sheets which were merged into PISM itself a few years later.) The EGU citation on her work, which has mostly been on the impact of large ice masses on global sea level change, says her papers are a “testament to her exceptional clarity of thought and physical insight.” Search “Winkelmann” in the publications page for many examples.

2017/04/27 13:25 · Ed Bueler


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: 2017/11/26 19:47 by Ed Bueler
© 2016 by PISM | webmaster