GFDL - Geophysical Fluid Dynamics Laboratory


The Modular Ocean Model (MOM) is the canonical global ocean circulation model used by many researchers around the world. The model’s origins date back to the community code first developed by Kirk Bryan and Mike Cox in the 1960’s-1980’s, and to which many other global ocean models can trace their origins. Ron Pacanowski, Keith Dixon and Tony Rosati fundamentally reworked these older codes into a much more modern format in the early 1990’s, and Steve Griffies has led the continued development of MOM since 2000. However, MOM is truly a community code, and many people, both inside GFDL and around the world, have contributed fundamentally to its successful development over the years.

  • MOM5.0 was released in 2012, and extends the capabilities of MOM4.1 with a novel “Lagrangian-blobs” treatment of overflows, and a prototype C-grid discretization.
  • MOM4.1 was most recently released in December 2009 (click here for the MOM4.1 manual: ~7Mb). This code allows for the following added functionality relative to MOM4.0:
    1. the inclusion of non-Boussinesq effects (relevant for studying sea-level)
    2. alternative vertical coordinates such as p* and z*.

We highlight also the release of the CM2.1 climate model as a test case with the December 2009 version of MOM4p1.

Earlier versions of MOM are:

  • MOM4.0 presented an extensive update in parameterizations and streamlined capabilities relative to MOM3. There were four sub-releases of this code during the period Jan2004 until May2005. The MOM4.0 manual was published as technical report #5 (~2Mb).
  • MOM3 is a z-coordinate model released in 1999. It is no longer supported by GFDL. The MOM3 manual was published as technical report #4 (~5Mb).
  • MOM2.2 was released in 1996. It is no longer supported by GFDL. The MOM2 manual was published as technical report #3 (~2Mb).
  • MOM1 was released in 1991. It is no longer supported by GFDL. The MOM1 manual was published as technical report #2 (~530kb).
  • The “Cox code” was released in 1984. It is no longer supported by GFDL. A guide was published as technical report #1 (~7Mb).

An unofficial history of ocean model development at GFDL has been prepared by contemporary ocean model developers and users.

Plans for MOM6

MOM6 represents a significant re-engineering of MOM employing an Arakawa C-grid for the horizontal (instead of a B-grid) and a radically different approach for the treatment of the vertical coordinate. MOM6 uses the ALE algorithm (Arbitrary-Lagrangian-Eulerian, [Hirt et al., 1974]) in the vertical that is coordinate-agnostic and thus allows remapping to any coordinate system as needed. Using ALE in the vertical also removes the advection CFL restriction on time-step so that the model is unconditionally stable to thin (or vanishing) layers.

In addition to generalized vertical coordinates, new capabilities in MOM6 include the conservative representation of wetting and drying essential for evolving ice shelf grounding lines, along with key physical parameterizations including new scale-aware parameterizations for eddy-permitting regimes. MOM6 will be the ocean code used in the next GFDL coupled climate model.

MOM6 will be made available under an open-development software-model which means that in addition to supported releases of the source code it will be possible for community developers to obtain and collaborate on the latest development branches. Support for MOM6 will begin with the first official release of software and documentation. In the meantime, the development branch of MOM6 is available via the MOM6 GitHub wiki.