Documentation for PISM, the Parallel Ice Sheet Model

All PISM News Items

Version 1.2

We are pleased to announce the release of the Parallel Ice Sheet Model (PISM) v1.2.

Compared to v1.1, the new version includes

  • modifications required by ISMIP6 experiments,
  • the frontal melt parameterization by Rignot et al (,
  • the orographic precipitation following Smith and Barstad, A linear theory of orographic precipitation (2004),
  • the ability to use NCAR ParallelIO for better I/O performance,
  • numerous bug fixes and minor improvements.

Please see the change log for a complete list.

2020/02/13 19:49 · Constantine Khroulev

MPI-M Hamburg, Germany: open postdoc for coupled atmosphere-ocean-ice sheet model

The Max Planck Institute for Meteorology (MPI-M) contributes to the BMBF project “From the Last Interglacial to the Anthropocene: Modeling a Complete Glacial Cycle” (PalMod,, which aims at simulating the climate from the peak of the last interglacial up to the present using comprehensive Earth System Models. Phase II of this project has an open position Postdoctoral Scientist (W073). The successful candidate will be part of a local team performing and analysing long-term transient simulations covering the last glacial and the transition into the Holocene with an interactively coupled atmosphere-ocean-ice sheet model. Additionally, the candidate will contribute to the continued development of this model. The model system consists of the MPI-Earth system model, the ice sheet model PISM, and the solid-earth model VILMA.

For further information regarding the job description, please contact Uwe Mikolajewicz (uwe.mikolajewicz(at) Do not forward your application to this email address; see links at the official announcement.

2020/02/05 17:00 · Ed Bueler

AWI PostDoc: "Antarctic Ice Sheets in warming climates"

Dr. Lohmann's group at AWI is seeking a postdoc to work with PISM and the multi-scale Earth system model AWI-ESM. See

2020/01/23 17:34 · Ed Bueler

PISM now uses Slack

PISM now has a Slack workspace. You can join us via the link Slack invite for PISM Help

We hope this will streamline our handling of user questions, and speed up our response time. Also, the more PISM users sign up, the more we will be able to help each other out.

2019/12/16 19:51 · Andy Aschwanden

PhD Studentship: Palaeoglaciology of Eurasian Ice Sheets

Dr. Ely's group at the University of Sheffield is advertising for a PhD student in paleo-ice sheet modeling, possibly including PISM:

2019/12/05 17:11 · Ed Bueler

Two ice sheet modeling postdocs at University of Alaska Fairbanks

The University of Alaska Fairbanks invites applications for two postdoctoral scholars in ice sheet modeling. The positions are based at the Geophysical Institute, a world-renowned institute for Arctic research. Our team in the glaciology group is a dynamic, international, and interdisciplinary team, and welcomes all kinds of people who share our values of curiosity, creativity, and initiative.

Project 1: Greenland

The goal of this project to improve the representation of the processes “where the ice meets the ocean” in a high-resolution whole-ice sheet model. This is a crucial step on the way to the ultimate goal of fully coupled high-resolution ice-ocean-atmosphere models, which are currently not in the realm of the possible.

The project is in collabration with Drs Patrick Heimbach and Feras Habbal at University of Texas at Austin. The successful candidate will use the Parallel Ice Sheet Model (PISM) and implement frontal melt parameterizations currently being developed by Drs Heimbach and Habbal, as well as contribute to the development. Frequent telecoms and annual visits are an integral aspect of the project.

Project 2: Antarctic Peninsula

The interactions between prevailing winds and mountain topography give rise to order-of-magnitude variations in precipitation For mountain ranges in which ice overtops the bedrock to form ice sheets these orographically driven feedbacks between precipitation and surface topography occur on timescales much shorter than for normal mountain building. The Antarctic Peninsula is an archetype of these feedbacks. It is aligned perpendicular to the prevailing winds and precipitation ranges from as high as 10 m/yr on the wet side of the mountain range to 10 cm/yr on dry side over less than 50 km. Despite the low snowfall on the dry side, the northern Antarctic Peninsula hosts large trunk glaciers like Crane, Flask and Leppard. We hypothesize that the feedbacks between orographic precipitation, ice dynamics, and thermodynamics drive asymmetry in the topography and behavior of the ice sheet.

This project is a collaboration with Dr Erin Pettit (Oregon State University) and Dr Gerad Roe (University of Washington). The successful candidate will implement an orographic precipitation module into the Parallel Ice Sheet Model (PISM) and conduct the proposed research with the coupled ice dynamic-orographic precipitation model. Frequent telecoms and annual visits are an integral aspect of the project. 


  • PhD in Glaciology, Geophysics, Physics, Math, or related field.
  • Experience in numerical modeling and scientific computation on high-performance computers.
  • Experience with ice sheet modeling is required and experience with the Parallel Ice Sheet Model is an asset.
  • A peer-reviewed publication record that is commensurate with experience.
  • Applicants should have excellent English language skills and enjoy working in an international and interdisciplinary team.

The positions are for a fixed term of 1.5 years with an anticipated starting date of Spring 2020. Interested candidates should contact Dr. Andy Aschwanden ( with a CV including information on your academic background, experience in glaciology/modeling/programming, field experience, publication record, and contact information of 2-3 referees (only email addresses), and any other relevant information..

The call is open until the positions are filled.

Fairbanks is a city in the heart of sub-Arctic Alaska, with out-the-front-door access to unparalleled wilderness for skiing, paddling, fishing, and hunting. It is a vibrant community with a strong university presence. More information about life in Fairbanks is available at

As a public, regional, comprehensive university, UAF is committed to building a culturally diverse and inclusive organization and strongly encourages women, minorities, individuals with disabilities, and veterans to apply. UA is an AA/EO employer and educational institution and prohibits illegal discrimination against any individual:

2019/12/05 00:33 · Ed Bueler

PISM (and other source codes) go into cold storage

In February they are going to put PISM in the bottom of an old coal mine in Svalbard:

GitHub Archive Program, with video.

But don't worry. Development continues.

2019/11/21 03:33 · Ed Bueler

Postdoctoral Scientist: ice-sheet/climate modeller at MPI-M (Hamburg)

The MPI-Earth group at MPI-M (Hamburg) is looking for a postdoc. PISM experience “would be of advantage”. For more information see the CRYOLIST post.

2019/06/17 23:28 · Ed Bueler

the 100th PISM-using paper!

At the end of May we found the 100th PISM-using paper:

L. B. Stap, J. Sutter, G. Knorr, M. Stärz, G. Lohmann (2019) Transient Variability of the Miocene Antarctic Ice Sheet Smaller Than Equilibrium Differences. Geophysical Research Letters 46 (8) pp. 4288–4298

See the publications page for a complete-as-far-as-we-know list of the first 100 published PISM applications, back to the first one in 2007.

We find PISM-using papers by following citations, so there may be others out there we do not know about. Authors who want to help us keep track should follow the advice at the acknowledgments documentation.

Here is one view of the PISM papers, sorted by the not-to-be-trusted “journal impact factor” of the journals in which they appear:

The most popular five journals for PISM papers are The Cryosphere, Journal of Glaciology, Journal of Geophysical Research: Earth Surface, Nature, and Geophysical Research Letters; excellent journals all. (Figuring-out the rest of journal abbreviations is an exercise for the reader.)

It is interesting to note that only 22% of PISM-using publications have a UAF-based co-author:

PISM is a tool used throughout the world by scientists needing an ice sheet model, whether or not they have a connection to the UAF developers. So we appreciate NASA and NSF support here at UAF, which has always made our open-source release model possible. We continue to push PISM development in a variety of directions, and we look forward to seeing the next 100 PISM papers!

See also this GI write-up.

2019/06/10 07:20 · Ed Bueler


The UAF PISM developers are currently busy getting PISM ready for ISMIP6. We are implementing all the required parameterizations for Greenland and we are making it easy to output fields in the requested MKS system, use the ISMIP6 variable names and output the requested fields with a shorthand.

Stay tuned.

2019/04/30 16:51 · Andy Aschwanden

Version 1.1

PISM v1.1 was tagged on 7 December 2018. It includes a large number of model improvements and issue resolutions (see the change log), but it is an incremental release. Please use this version, or the (master branch), unless you have a good reason to use an older one!

2018/12/10 21:16 · Ed Bueler


LARMIP is the Linear Antarctic Response to basal melting Model Intercomparison Project. PISM is one of several participating models. The goal is to use the newest models to compute a linear-response sea level contribution to inform the IPCC-AR6. Find all necessary materials at

2017/11/27 04:56 · Ed Bueler

PhD opportunity in ice-ocean interaction (modeling)

The Geophysical Institute of the University of Alaska Fairbanks is seeking a PhD student for the recently funded NSF project “Understanding the controls on spatial and temporal variability in ice discharge using a Greenland-wide ice sheet model”. The overall goal of this project is to develop novel parameterizations of ice-ocean interaction that are suitable for large scale ice-sheet modeling. The interdisciplinary project is co-led by Andy Aschwanden (UAF; ice sheet modeling) and Patrick Heimbach (U Texas at Austin, ocean modeling) and comprises two PhD positions, one focussing on the ocean side (see separate announcement) and the other on the ice sheet side (this posting). The student here at UAF will implement and test parameterizations within the framework of the Parallel Ice Sheet Model (PISM) but will closely collaborate with U Texas, including mutual visits.

We seek motivated candidates with a degree (preferably a M.Sc. or equivalent) in geosciences, physics, mathematics, engineering or related fields. Basic experience in numerical modeling, good oral and written communication skills are a prerequisite.

For more information, please contact Andy Aschwanden (

2017/11/21 18:32 · Ed Bueler

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
2017/11/05 07:28 · 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

2017/10/20 02:16 · 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 17:50 · 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 21:25 · Ed Bueler

New PISM user help email:

The core team at UAF continues to support PISM users. The new email for help is; it replaces As before, email to this address will be distributed to all the UAF developers, and so it will get the most prompt response year-round.

2017/02/22 05:47 · Ed Bueler

Study of Juneau Ice Field in Cambridge Core news

A recent PISM application Ziemen et al (2016) is covered by a news item in Cambridge Core news.

The 4000 square km ice field in Southeast Alaska is well-known and accessible since its outlets are in the suburbs of the Alaska state capital, Juneau. But climate data for the area are sparse.

Those model runs that agreed well with observations for 1971 to 2010 generated volume and area losses of more than half by 2099. While co-author Regine Hock (UAF) is quoted as saying “The massive icefield that feeds Alaska’s Mendenhall Glacier may be gone by 2200 if warming trend predictions hold true,”, the authors emphasize that spatially-distributed mass balance measurements and improved climate projections that resolve the local temperature and precipitation patterns are essential to solidifying these predictions.

2016/10/06 22:26 · Ed Bueler

Reminder for authors of PISM-using papers

Please acknowledge the funding that makes PISM possible, and which supports its continued maintenance and technical support. Include the sentence “Development of PISM is supported by NASA grants NNX13AM16G and NNX13AK27G.” in the Acknowledgments part of your paper.

If authors do this consistently then it will help to ensure continued funding of PISM!

For specific suggestions on how to cite the design or justification of PISM see this page.

2016/08/18 19:44 · Ed Bueler

PostDoc in ice sheet and climate modelling at AWI Bremerhaven, Germany

The Paleoclimate Dynamics section at Alfred-Wegener-Institut invites applications for a position as a

PostDoc scientist

with a background in ice sheet or climate modelling for the DFG-project “Global sea level change since the Mid Holocene” (SPP 1889).

Background and tasks:

The aim of this project is to study the evolution of polar ice sheets of the last 6000 years and to estimate the role of climate – ice sheet interactions. Combining climate and ice sheet simulations of different resolution, the project particularly focusses on the ice sheets' mass balance and on ice shelf – ocean interactions under natural and anthropogenic climate change.

The postdoc’s duties will include set-up, supervision, and analysis of climate and ice sheet (PISM) simulations as well as publication in peer-reviewed journals.


The successful candidate should have a PhD in glaciology, atmospheric sciences, oceanography or related sciences and should have a background in either ice sheet or climate modelling.

The position is limited to 3 years, starting August 1st, 2016 or later. The salary will be paid in accordance with the German Tarifvertrag des öffentlichen Dienstes (TVöD Bund), salary level 13. The place of employment will be Bremerhaven.

For further information:

2016/06/15 15:49 · Ed Bueler

PISM stable/dev and PETSc 3.7

PETSc 3.7 was released on April 25, 2016. We are currently working on making PISM compatible with PETSc 3.7 and will announce it here as soon as possible.

In the meantime, please install petsc 3.6.4 from here. PISM version 0.7 (stable0.7 branch) works with any PETSc 3.5.X and higher.

2016/04/27 16:54 · Andy Aschwanden

Greenland outlet glacier flow modeled the right way

Today's publication of Aschwanden et al. (2016) in Nature Communications is certainly a milestone in PISM development. However, it is also a milestone in ice sheet modeling generally. Here's why.

The paper is based on PISM simulations with grid resolution down to 600 m over the entire Greenland ice sheet. To start, each of an initial ensemble of 14 lower-resolution (1500 m) experiments has a single ice-sheet-wide value for all parameters. The best of these, in an ice-sheet-wide measure, is re-run at the 600 m resolution and various coarser resolutions. The quality of this flow model for 29 outlet glaciers is assessed; each outlet glacier sees the same physics. The main result is that the majority of the outlet glaciers show strong correlation between modeled and present-day-observed velocity, when it is compared along cross-flow and near-ocean profiles.

Before this paper one might suppose, based on the most prominent literature on the subject, that a detailed, measurably-accurate, outlet-glacier-resolving model of the present-day velocity of an entire ice sheet was dependent both on removing shallow assumptions from the stress balance and on tuning a very large number of basal parameters. Both of these “required” properties would be very bad news for the prospect of using ice sheet simulations to do science! On the one hand, Stokes models are computationally-expensive, while on the other hand only present-day, and not past or future, data are available to set all these basal parameters through inversion.

Such a pessimistic view turns out to be substantially false. Aschwanden et al. (2016) show that four things do matter: (i) an accurate map of bedrock topography, (ii) a stress regime in which viscous membrane stresses are part of the balance with basal sliding resistance, (iii) an energy-conservation-driven basal stress model derived (conceptually) from a model of a wet, pressurized, deformable basal layer, and (iv) high model resolution over all areas of the ice sheet where sliding is possible and/or steep/rough basal topography exists.

NASA IceBridge missions, and the mass-conserving-bed technology of Morlighem et al (2014), are shown by this paper to represent major progress on item (i). Items (ii) and (iii) are properties of the PISM continuum model, and item (iv) of its implementation as parallel-scalable software. Certainly all of these “things that matter” are improvable. More-complete stress balances and the use of inversion of present-day velocities will both be essential to improvements. The main idea remains, however: if the modeled flowing ice has the right bottom geometry, and if the dynamical model has certain key features, then the resulting dynamics are already inside the ballpark!

This research has been featured in Alaska's largest newspaper, the Alaska Dispatch News.

2016/02/01 20:49 · Ed Bueler

Ph.D scholarship at Victoria University Wellington: Antarctic ice-sheet modelling

See the official announcement for complete details.

The Antarctic Research Centre, Victoria University of Wellington, New Zealand, is offering a FULLY FUNDED scholarship for an enthusiastic and talented Ph.D student to undertake numerical ice-sheet modelling research. Experiments will focus on better understanding and simulating the processes involved in ice-sheet – ocean interactions. Such processes determine the basal mass balance of marine-based ice-sheets such as the West Antarctic Ice Sheet, and as such, control the pattern and timing of grounding-line migrations.

Collaborating with scientists at a variety of New Zealand (VUW, GNS, NIWA) and Australian (UNSW, UTAS, AAD) institutions, the researcher will use present-day glaciological and oceanographic observations as primary constraints to a suite of model simulations that will explore the sensitivity of Antarctic ice-sheets to changes in ocean circulation. A key aspect of the project lies in trying to identify and quantify thresholds and feedback mechanisms that may either accelerate or inhibit ice-shelf melt. The ultimate aim of the project is to build on recent work to provide more robust simulations of ice-shelf and ice-sheet changes under future scenarios of perturbed atmospheric and oceanographic conditions.

The research project will span a range of temporal and spatial scales, but will primarily use the Parallel Ice Sheet Model and will focus initially on the Ross Ice Shelf. The successful applicant may also have the opportunity to spend time in Antarctica acquiring new data.

Skills: Applicants must have a strong background in geophysics, maths or other numerical Earth Sciences. Experience working in a UNIX / Linux environment, including shell scripting, is essential. Programming abilities in any of the usual languages and experience with high-performance computing facilities would also be extremely useful.

Applications: We wish to have the successful applicant starting no later than July 2016, and therefore request completed applications by 18th December 2015.

For details of the application process or to lodge an expression of interest, contact Dr. Nick Golledge ( as soon as possible.

2015/11/25 03:31 · Ed Bueler

Nothing to stop WAIS deglaciation after Amundsen Sea retreat?

A new paper in the Proceedings of the National Academy of Sciences by J. Feldmann and A. Levermann, of the Potsdam Institute for Climate Impact Research, uses PISM simulations to show that nearly-complete WAIS collapse is triggered by present-day melt rates in the Amundsen Sea. Modeled WAIS deglaciation follows after relatively-short (60–200a) periods in which the present-day sub-shelf (i.e. ocean-caused) melt rates are sustained.

The simulations use conservative assumptions about, and (necessarily) modeling of, the interaction of the ice sheet with the ocean and atmosphere. In particular, subshelf melt rates for the present ice shelf geometry are taken from Finite Element Sea Ice-Ocean Model (FESOM) results. These are then extended to the evolving cavity geometry by a diffusive algorithm into regions below sea level, but with a pressure adjustment using the ice shelf base elevation. This leads to melt rates further inland that are similar to corresponding present-day-cavity-geometry-induced melt rates.

In most other ways this application of PISM is as expected, though at high (5km) resolution and using a full suite of marine ice sheet submodels: 50ka spinup, SIA+SSA model with plastic till, subgrid motion of the calving front, ocean-water stress boundary condition at the calving front, the "eigen-calving" calving law, and an interpolated grounding line.

The results of the simulations are most easily understood by seeing what happens:

This work appeared today, 2 November 2015. It is already featured in commentaries at the Washington Post, The Guardian, and Bloomberg Business News. It is also featured in Nature journal's "News:Explainer", and in Science magazine's "Latest News".

The last of these includes this high-level view from two well-known students of the behavior of Amundsen Sea-sector glaciers:

“This paper does confirm what we hypothesized, that knocking out the Pine Island Glacier and Thwaites takes down the rest of the West Antarctic Ice Sheet,” says Ian Joughin, a glaciologist at the University of Washington, Seattle, who co-authored last year’s Science paper. He adds, however, that the model’s weakness is its [temporal] resolution; it shows the destabilization of the glaciers occurring roughly 60 years from now, whereas present observations suggest that collapse is already underway. As a result, Joughin says, the model’s time scale for the collapse is probably too long. “It’s more likely measured in centuries rather than millennia.”
Indeed, “the jury is still out” on whether Feldmann and Levermann’s study got the time scale right, [Eric] Rignot [of the University of California, Irvine] says. The long-term evolution of an ice sheet “is a very complex modeling problem. Some of the variables controlling the models are not all that well known,” he adds, including forces such as winds, ocean circulation, and how icebergs calve. “There is not a model out there that is getting it right, because they all have caveats. I think the discussion is ongoing, and is only going to be more interesting with time.”
2015/11/03 01:14 · Ed Bueler

Local Fairbanks paper features PISM

As a result of the buzz around Winkelmann et al. (2015)'s modeling of the effect of full conversion of available fossil fuels in the ground into atmospheric CO2, using PISM for determining ice dynamics/response timescale, on 5 October our local paper the Fairbanks Daily News Miner featured PISM. The content is a bit warped by scientist-to-journalist transmission issues, but we are happy to have local recognition of this UAF-lead project!

2015/10/13 18:13 · Ed Bueler

PhD position at ETH Zurich in paleo-ice sheet modelling

See the official position announcement here.

We are looking for a candidate who is interested in taking part in the research project “Modelling the ice flow in the western Alps during the last glacial cycle” which is a joint initiative between ETH Zurich and the University of Bern (Prof. Christoph Raible and Dr. Juan Jose Gomez-Navarro). The objective is to better understand the chronology of the last glaciation over the Alps via a modelling approach. The core of this doctoral research will be to model the ice flow and the glacial extent in the western Alps during the last glacial cycle. For that purpose, the PhD student will set up and run the Parallel Ice Sheet Model (PISM) on the clusters of the Swiss National Supercomputing Centre. The crucial step in setting up in PISM will be to include high-resolution climate simulation results, which will be conducted at the University of Bern. The combination of the two state-of-the-art models (ice flow and climate) will give a new insight of the ice flow field prevailing in the western Alpine region during some periods of interest like the last glacial maximum (22000 BP) and an earlier period (65000 BP). The final goal of the PhD will be to compare the new model results to the geomorphological evidence left on the Swiss landscape during the last glacial cycle (e.g. moraines, erratic boulders) in collaboration with quaternary geologists of EHT Zurich. The PhD student will be supervised by Dr. Guillaume Jouvet and Prof. Martin Funk.

The ideal candidate has a master degree either in geophysics, earth sciences, physics, applied mathematics, computer science, or a related field, and a keen interest in modelling of geophysical processes. Previous experience in computer modelling and scientific programming languages (C/C++, Python, Matlab) is an asset. Good writing and communication skills as well as the motivation to fruitfully collaborate within an interdisciplinary framework are essential, in particular with our climate modelling partners at the University of Bern.

For additional information please refer to or contact Dr. Guillaume Jouvet, (no applications).

2015/10/13 18:03 · Ed Bueler

What would happen in Antarctica if all fossil fuels are burned?

A new open-access paper by Ricarda Winkelmann and others uses PISM to address an admittedly extreme question: If all currently-attainable fossil fuel resources are converted to atmospheric greenhouse gases, what happens to the Antarctic Ice Sheet?

This paper's model-based answer is that serious destruction of the ice sheet occurs in the first millenium, at about 3 m sea level rise per century. Such a large mass loss rate tails off in the two following millenia. The large losses come from a combination of marine-ice-sheet instability and surface elevation versus mass balance feedback, both of which are modeled effects in PISM. However, in the first century of the simulations there are the same relatively-modest AIS mass changes as seen in other recent modeling work, because dynamic losses driven by increasing ocean temperatures are partly offset by increasing snowfall.

Here is a quick methods summary, with more detail found in the paper and its supplementary material: Emission scenarios, CO2 concentrations, and global mean temperature pathways are combined in an Earth system model and then downscaled to surface and ocean temperature anomalies for Antarctica. These regional warming scenarios are then used to force PISM, in particular using its positive-degree-day scheme to model surface melt and a three-equation model for subshelf melting.

US National Public Radio featured the paper, including comments by co-author Ken Caldeira, on the 11 September edition of All Things Considered, as did the New York Times.

2015/09/12 18:35 · Ed Bueler

Postdoc for ESM/PISM modeler (MPI-M Hamburg)

This is a re-posting of the CRYOLIST announcement from Uwe Mikolajewicz

The Max Planck Institute for Meteorology (MPI-M) is a multidisciplinary center for climate and Earth system research located in Hamburg, Germany. MPI-M contributes to the BMBF project “From the Last Interglacial to the Anthropocene: Modeling a Complete Glacial Cycle” (PalMod), which aims at simulating the climate from the peak of the last interglacial up to the present using comprehensive Earth System Models.

With respect to this research project, we have an open position for a

Postdoctoral Scientist (m/f, Ref. MPIM-W009)

The successful candidate will be part of a local team performing and analyzing transient simulations from the last Glacial to the Holocene with an interactively coupled atmosphere-ocean-ice sheet model. Additionally the candidate will contribute to the development of this model. The model system will consist of the MPI-Earth system model and the ice sheet model PISM.

  • A PhD in oceanography/meteorology/physics or a related science.
  • Experience in performing and analyzing experiments with a comprehensive earth system model or ice sheet model;
  • Strong motivation and ability to carry out model development in an interdisciplinary and international environment;
  • Ability and desire to work in a closely cooperating team;
  • Excellent communication skills and publication record;
  • Familiarity with coding and running computer models, very good programming skills in FORTRAN (on a Linux platform) and scripting;
  • Knowledge of the MPI-Earth system model or the ice sheet model PISM would be of advantage.

more details

Additional PhD Fellowships

For information on PhD Fellowships in Earth System Modeling at MPI-M, see

2015/08/17 16:40 · Ed Bueler

PISM version 0.7.1 and PETSc 3.6.1

PISM v0.7.1 was released 30 June 2015. In addition to bug fixes this version adds support for PETSc 3.6.1, which was released 22 July 2015.

PETSc 3.6.0 is not supported due to a bug in PETSc. Please use PETSc 3.5.4 or >= 3.6.1 with PISM.

2015/06/30 17:45 · Constantine Khroulev

Summer time

It's summer time! UAF PISM developers are currently writing proposals, working on their own projects, and enjoying the summer. Please give us some slack responding to questions, bug reports, etc. We will try to fix serious bugs as quickly as possible . We'll be back at full strength in the Fall.

2015/06/23 20:17 · Andy Aschwanden

PISM version 0.7 and PETSc 3.6

PETSc 3.6 was released on June 9, 2016. We are currently working on making PISM compatible with PETSc 3.6 and will announce it here as soon as possible.

In the meantime, please install petsc 3.5.4 from here. PISM version 0.7 (stable0.7 branch) works with any PETSc 3.5.X.

2015/06/16 17:47 · Andy Aschwanden

PISM version 0.7 is out

Major PISM release

This release has substantial changes to the code base, but users will not see large differences. The goal of most code changes is to improve maintainability, and our speed in fixing bugs and adding features, so we ask users to update from v0.6 unless they have a good reason against it.

If you already have a git repo for pism then upgrade by doing

git fetch origin
git checkout stable0.7

in the PISM source tree. (Or get a new tagged .tar.gz or .zip at Then do

make install

in the build directory.

The install directions in, included in the source release, should help with installation errors, but there is also an Installation Manual. Feel free to email with installation questions; please include the failed commands and the error message(s).

Lists below give user-visible changes. For a full list of changes since v0.6, please see in the source release.

Installation changes

Click here to see the list

New physical model features

Click here to see the list

New and renamed diagnostics

Click here to see the list

Changes which might break run scripts

Click here to see the list

Getting more help

Please send email to for help with any version of PISM.

2015/05/13 03:07 · Ed Bueler

PISM at AGU 2014

At the AGU Fall Meeting 2014, PISM simulations and results were featured in a number of posters and oral presentations.


oral presentations

2014/12/23 17:53 · Ed Bueler

PISM v0.6.2 is out

This minor release fixes several bugs and adds PETSc 3.5.x support.

Full list of changes since v0.6.1

If you have questions about installing or using PISM, you can reach UAF developers by sending an e-mail to

2014/11/07 00:22 · Constantine Khroulev

PISM models the Antarctic contribution to meltwater pulse 1A

In a new Nature Communications paper, researchers at Victoria University and the University of New South Wales describe a model study of Antarctic ice sheet evolution over the last 25 kyr using PISM with ocean-forcing inputs from the Earth system model LOVECLIM. They show that when the ocean around Antarctica becomes more stratified, warm water at depth melts the ice sheet faster than when the ocean is less stratified.

The study used a large ensemble of 15 km PISM simulations in a data-constrained mode. In the simulations that best fit a variety of temporal and spatial observations, several episodes of accelerated ice-sheet recession occurred, with the timing of the largest being coincident with meltwater pulse 1A. This episode saw an abrupt rise in global sea level, with an Antarctic contribution of nearly three meters over just a few centuries.

Both this blog entry and this Science Daily news item summarize the work and relate the modeled melt from 14,000 years ago to present-day Antarctic conditions.

2014/10/09 02:16 · Ed Bueler

Mass-conserving subglacial hydrology in PISM

In a Geoscientific Model Development Discussion paper, UAF author Ed Bueler and IMAU author Ward Van Pelt describe PISM's new mass conserving subglacial hydrology models.

For the PISM user with an interest in subglacial hydrology this paper provides a detailed description of all the subglacial hydrology models available in PISM versions v0.6 and above, along with a stability analysis, verification, and an application to the Greenland ice sheet.

2014/07/29 18:27 · Andy Aschwanden

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 Then do “make install” in the build directory.

For a full list of changes since v0.6, please see

Send email to for help with any version of PISM.

2014/06/01 00:48 · 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.

This Science Daily news item quotes the authors about this work.

2014/05/05 19:35 · Ed Bueler

PISM stable0.6 is out

See the stable version page to check out a copy of the PISM stable0.6 source code. If you have already checked out the prerelease version, just do git pull and then make install in your build directory. Send email to for help with any version of PISM.

Changes since stable0.5 include

Basal strength and basal hydrology

Click here to see the list

Marine ice sheet modeling

Click here to see the list

Climate inputs and ocean inputs

Click here to see the list

Inverse modeling tools are a part of this release

Please see the PISM's Python Documentation.

Energy and mass model improvements

Click here to see the list

Improved User's Manual examples

Click here to see the list


Click here to see the list

Under the hood

Click here to see the list

2014/02/14 03:18 · Constantine Khroulev

The first seven PISM PhDs

Since 2012 there have been seven Ph.D. students who have completed their degrees using PISM as a major tool in their research. The new year is a good time to feature their accomplishments on the PISM front page!

Dr. Torsten Albrecht

A dynamic memory of fracture processes in ice shelves, Ph.D. Potsdam University 2013; advisor A. Levermann; publications including Albrecht et al. (2011) and Albrecht and Levermann (2012); personal webpage

Dr. Marijke Habermann

Basal shear strength inversions for ice sheets with an application to Jakobshavn Isbrae, Greenland, Ph.D. University of Alaska Fairbanks 2013; advisor M. Truffer; publications including Habermann, Truffer, and Maxwell (2013); personal webpage

Dr. Maria Martin

Numerical simulation of the Antarctic ice sheet and its dynamic response to external perturbation, Ph.D. Potsdam University 2012; advisor A. Levermann; publications including Martin et al. (2011); personal webpage

Dr. Ward van Pelt

Modelling the dynamics and boundary processes of Svalbard glaciers, Ph.D. Universiteit Utrecht 2014; advisor J. Oerlemans; publications including van Pelt and Oerlemans (2012) and van Pelt et al. (2013); personal webpage

Dr. Anne Solgaard

Large-scale modeling of the Greenland Ice Sheet on long timescales, Ph.D. University Copenhagen 2012; advisors C. Hvidberg and G. Adalgeirsdottir; publications including Solgaard et al. (2011), Solgaard and Langen (2012), and Solgaard et al. (2013); personal webpage

Dr. Ricarda Winkelmann

The future sea-level contribution from Antarctica: Projections of solid ice discharge, Ph.D. Potsdam University 2012; advisors S. Rahmstorf and A. Levermann; publications including Winkelmann et al. (2011), Winkelmann et al. (2012), Winkelmann and Levermann (2013); personal webpage

Dr. Florian Ziemen

Glacial climate variability, Ph.D. Universität Hamburg 2013; advisor U. Mikolajewicz; personal webpage

2014/01/09 05:24 · Ed Bueler

Continued NASA funding supports PISM development through 2017

We have been notified that two PISM-supporting NASA research proposals have been selected for funding, one in the Cryospheric Sciences program and one in the Modeling, Analysis, and Prediction (MAP) program. Our proposed research threads focus on the dynamics of the Greenland ice sheet and on the exploitation of NASA remote observations as constraints. The current MAP grant expires in the next few months, so this news is timely. The new grants support PISM development and application for four years, through mid-2017. They include support for UAF researchers Ed Bueler, Andy Aschwanden, and Mark Fahnestock, and full-time support for scientific programmer Constantine Khroulev.

2013/03/05 05:26 · Ed Bueler

2012 was a good year for authors using PISM

In 2012 ten papers were published by scientists using PISM. The articles appeared in these journals:

  • Nature
  • Proceedings of the National Academy of Sciences
  • Geophysical Research Letters
  • Quaternary Science Reviews
  • Climate Dynamics
  • The Cryosphere (2 papers)
  • Journal of Glaciology (3 papers)

For details see the PISM Publications tab.

2013/01/13 07:47 · Ed Bueler

AGU 2012

At the AGU Fall Meeting 2012, PISM was prominently featured in several oral presentations.

Speakers presenting PISM results in the video-taped session “C43F: Cryospheric Contributions to Sea Level Rise: Current Estimates and Projections” include

  • Andy Aschwanden: Greenland mass changes from 1960 to 2100: Hindcasting and forecasting with PISM and RACMO2/GR (starting at 40.0)
  • Bob Bindschadler: Ice-Sheet Model Sensitivities to Environmental Forcing and Their Use in Projecting Future Sea-Level (The SeaRISE Project) (starting at 1:32.0)
  • Sophie Nowicki: Future response of the Greenland and Antarctic ice sheets: the SeaRISE experiments (starting at 1:45.0)
  • Anders Levermann: Snowfall increases future ice discharge from Antarctica (1:57.0)

Watch the session online:

2013/01/08 20:20 · Andy Aschwanden

PISM stable0.5 is released

See the stable version page to check out a copy of the PISM stable0.5 source code. If you have already checked out the prerelease version, just do “git pull” and then “make install” in your build directory. Send email to for help with any version of PISM. See also slides introducing stable0.5 at the European PISM workshop, Hamburg, Germany, May 2012.

Changes compared to stable0.4 include

Most-significant changes

Click to show the list…

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  • Added regional modeling executable pismo and Python drainage-basin tools regional-tools.
  • Added Jakobshavn outlet glacier model example. See the User's Manual.
  • Separate documentation of climate forcing options in the new PDF PISM's climate forcing components manual.
  • Consistent command-line options for climate forcing, based on improvements to climate forcing code and its interface.
  • Separated flow laws used in SIA and SSA code, and thus separated enhancement factors. New command-line options (-sia_e, -ssa_e) and configuration parameters (sia_enhancement_factor, ssa_enhancement_factor).
  • -pdd_annualize implemented. This is recommended for degree-day melting scheme usage.
  • Reported rates of change are computed as average rates over reporting intervals, by differencing cumulative quantities.
  • Removed the pgrn executable and the EISMINT-Greenland example. All Greenland examples now use standard executable pismr. The documented SeaRISE-Greenland and Jakobshavn examples both use modern data, and fully-replace the old version.
  • Similarly, removed the EISMINT-Ross example and the pross executable. Replaced by improved, modern example using ALBMAP and MEASURES data. See the User's Manual.
  • Now using NetCDF4 so big files can be written (see this news item). New output format options -o_format [netcdf4_parallel, pnetcdf].
  • Moved source code hosting and bugs/issues to
  • Switched to PETSc 3.2.
More usability improvements and changes

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  • Implemented -o_order [xyz, yxz, zyx]; the first one is fastest.
  • Implemented -e_age_coupling.
  • Sliding model option -topg_to_phi now it takes 4 numbers (no special value in the ocean).
  • Time-series flush whenever -extra_files are written.
  • Model time in output files is in seconds.
  • PISM uses time bounds, both in reporting code and code using forcing data.
  • Reporting for both scalar and spatial time-series: daily, monthly, yearly.
Under the hood

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  • Improved the IceFlowLaw class by moving physical constants out of it.
  • Improved the implementation of PISM's basal yield stress model.
  • Improved regridding code.
  • Implemented temperature-dependent conductivity and specific heat capacity of ice.
  • Added support for the Gregorian calendar.
  • PISM uses Proj4 to compute latitudes, longitudes, and cell areas.
2012/07/14 01:02 · Ed Bueler

Parallel netCDF4 allows first Greenland simulation on a 1km grid

The upcoming stable 0.5 release supports parallel NetCDF4, thus avoiding the file size limitations of netCDF3. This allows for unprecedented grid resolutions.

Here at UAF we have performed the first Greenland 1km 100-year simulations, run in parallel on 512 cores.

Observed and modeled surface speeds in meters per year.

a) observed (Joughin et al., 2010)

b) PISM constant-climate initialization

c) PISM paleo-climate initialization

(click on the image for a bigger version)

2012/04/12 23:25 · Andy Aschwanden

1st European PISM Workshop in Hamburg, Germany, 21-22 May 2012

The European PISM (Parallel Ice Sheet Model) workshop will be held in Hamburg, Germany, from Monday, the May 21, 2012 (starting at noon), to Tuesday, May 22. Workshop information and registration is available at

Also see this poster.

2012/03/13 05:18 · Ed Bueler

We have moved (and switched to PETSc 3.2)

  • PISM now requires PETSc 3.2. For now, this change affects the development version, but the Spring 2012 stable0.5 release will be available at only and will not support PETSc 3.1 and earlier.

Read more

2011/11/10 17:45 · Constantine Khroulev

PISM at 5 years and r2000 on But we are moving!

As of 19 October 2011 we have committed 2000 revisions to PISM in the last five years, for an average of about one commit message per day. We can thank the generous public hosting of PISM at for this, and subversion too.

By the way, we are at least nine committers: Brown, Bueler, Khroulev, Shemonski, Aschwanden, Martin, Albrecht, Maxwell, Mengel. And quite a few other bug reporters and active users, too! Thanks to all.

But despite wallowing in nostalgia we are going to move source code hosts anyway!

The new host for PISM will be at github, and we will switch to using the git distributed version control system for managing PISM development. This is following the herd! However, with gna's unsigned certificate issues, and not quite keeping up to date, the UAF developers figure it is about time. We expect git will make improving the code easier after a bit of relearning version control. We will officially switch over pism-dev around November 1, but we will continue to host stable versions 0.1, 0.2, 0.3, 0.4 through If you are a PISM project member at you will get an invitation to be a collaborator at the new github site. (Or you can request to be a collaborator at the PISM github site.) Until that invitation announcing the move, please continue to use the host for commits, bugs, and tasks.

2011/10/20 07:06 · Ed Bueler

PISM stable0.4 is released

PISM version stable0.4 is available. See the stable version page to check out a copy of the source code or download an Ubuntu package. Send email to for help with any version of PISM.

Changes (compared to stable0.3) include

Model changes
  • Merging with PISM-PIK:
    • SIA and SSA ice velocities are hybridized using simpler technique (Winkelmann et al. 2011).
    • Mass continuity finite difference scheme is conserving (Winkelmann et al. 2011).
    • Mass fluxes at calving fronts are accounted by subgrid scheme (Albrechts et al. 2011).
    • Calving model based on principle strain rates (“eigencalving”; Winkelmann et al. 2011).
  • Improved enthalpy code (Aschwanden et al. 2011).
  • In stable0.3 and 0.2, stored basal water was diffused in the horizontal (Bueler & Brown, 2009). This regularization has been removed. Instead water is stored locally and drains at a fixed, configurable rate. Users/developers are encouraged to propose and implement alternative subglacial hydrology models.
  • Implemented the bed roughness parameterization for SIA described by (Schoof, 2003).
  • PDD code computes accumulation from precipitation and a temperature threshold.
  • Temperature, precipitation, surface mass balance lapse rate corrections can modify surface inputs.
Usability improvements/changes

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  • PISM stable0.4 requires PETSc version 3.0 or 3.1. (Version 2.3.3 is not supported.)
  • New CMake-based build system.
  • Forcing by time- and space-dependent climate or surface boundary conditions: improved interface.
  • Simplified flow-line modeling using PISM. See Storglaciaren example in the User's Manual (or see the worked-storglaciaren page for a preview).
  • On Debian and Ubuntu systems PISM can be installed from a .deb package. Download it here. This is no longer the case.
  • Building development version of PISM on Debian systems is easier with the help of a meta-package depending on all necessary tools and libraries; see dev version page.
  • Model state is backed-up every wall-clock hour to make it easier to re-start interrupted runs.
  • PDD code reports melt, accumulation and runoff.
  • Updated documentation, including User's Manual, Installation Manual, and Source Code Browser.
Under the hood

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  • Better software tests.
  • Less restrictive input file format means easier to create a PISM-readable NetCDF file.
  • Improved file output performance and choice of variable order.
  • Many structural improvements:
    • re-factored stress balance code
    • re-factored flow laws
    • well-defined climate forcing
    • well-defined “diagnostic” computations
    • isolated bedrock thermal layer model, with clear interface
  • More flexible climate forcing using scalar temperature offsets
  • Clearly-identified ice surface inputs will accept output from a snow/firn model.
Experimental features

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  • Finite-element-based SSA solver.
    • Designed for use with inverse modeling codes that are not a part of this release.
  • Preliminary regional (outlet glacier) modeling support.
  • Mostly untested coupling to external energy balance/surface mass balance models.
2011/05/31 19:18

Successful merge: PISM + PISM-PIK = (much better PISM!)

If you are following the development branch you know that much of the capability developed by Anders Levermann's group at the Potsdam Institute for Climate Impact Research (PIK) is now in PISM. The former PISM-PIK branch of PISM stable0.2 has merged with PISM. This major merge means that PISM is now a joint UAF-PIK project. Both groups are committed to supporting the new capabilities as an open, documented model.

This means all PISM users get a much improved marine ice sheet model, with better ice shelf calving front physics especially.

Our target for release of stable0.4 is May 2011. It will contain the PISM-PIK improvements identified in Albrechts et al. (2011), Martin et al. (2010), and Winkelmann et al. (2010).

2011/04/20 17:54

PISM stable0.3 is released

PISM version stable0.3 is available. See the stable version page to check out a copy of the source code. Send email to for help with any version of PISM.

Compared to stable0.2, the new version

  • uses a polythermal, enthalpy-based energy conservation scheme
  • includes improved atmosphere, surface processes and ocean model structure
  • puts all model parameters and physical constants in a configuration file which can be changed without re-compiling PISM
  • has a better User's Manual
  • comes with a command-line option Cheat-Sheet
  • has a better HTML PISM Source Code Browser
  • supports saving scalar, 2D and 3D diagnostics at given times during the run
  • allows climate forcing using spatially-varying “anomalies” (near-surface air temperature and precipitation)
  • includes better metadata handling
  • can be stopped and restarted without affecting results of a run
  • has more software tests (including regression tests)
  • has an automatic vertical grid extension mechanism
  • performs area and volume calculations using WGS84 datum to correct projection error
  • makes the computation of the age of the ice optional, for efficiency
  • has easier-to-extend source code
  • comes with three worked examples: Antarctica, Greenland, Storglaciaren
2010/04/21 21:53
old_news.txt · Last modified: 2014/04/01 21:27 by Ed Bueler
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