Publications

    DOME - Dynamics of Overflow Mixing and Entrainment

    Originally J. C. Stephens, 2000, Working Report. Geophysical Fluid Dynamics Laboratory, PO. Box 308, Princeton, NJ 08542, USA. 25pp. Currently supported by R. Hallberg.

    The far-reaching significance of deep cold temperatures in the ocean was first realized by Count Rumford in 1797. Rumford, in analyzing ship-recorded temperatures obtained almost 50 years earlier, inferred a polar origin for the deep water masses and a corresponding meridional overturning circulation to carry deep cold waters equatorward and warm surface waters poleward.

    We now know that this circulation is driven by heat and/or freshwater loss at the ocean surface in a few special regions near to the poles, and refer to it as the thermohaline circulation. This circulation transports a considerable amount of heat, and in so doing strongly moderates weather and climate. For this reason, in view of anthropogenically induced changes in atmospheric carbon dioxide and the resultant possibility of global warming, we need to understand how the oceans' role in storing and transporting heat will vary in response to climate change.

    The wealth of recent data from programs such as the World Ocean Circulation Experiment (WOCE) indicates clearly that ocean models are currently lacking in their representation of deep water mass properties and circulation. A significant part of this is likely due to the poor representation of intense mixing and bottom boundary processes occurring at overflows, where many deep and intermediate water masses are sourced. This is therefore one of the most important problems to be addressed in current ocean models.

    DOME is an international study to compare the performance of a number of state of the art ocean models in representing these processes, aimed at quantifying model performance and identifying areas for improvement in individual models.

    The original idea for some kind of comparison project to address overflow related issues was conceived in discussions between Robert Hallberg, Peter Killworth and James Stephens. This idea rapidly grew into what is now the DOME project. DOME has already attracted a great deal of interest, at this stage mostly from the large-scale numerical modeling community.

    DOME currently has the following participants:

    • Robert Hallberg (rwh@gfdl.gov)
    • Peter Killworth (peter.d.killworth@soc.soton.ac.uk)
    • Tal Ezer (tne@gfdl.gov)
    • Neil Edwards (nre@soc.soton.ac.uk)
    • Steven Alderson (sga@soc.soton.ac.uk)
    • George Nurser (agn@soc.soton.ac.uk)
    • David Holland (holland@cims.nyu.edu)
    • Dale Haidvogel (dale@imcs.rutgers.edu)
    • Paul Schopf (schopf@cola.iges.org)
    • Whit Anderson (anderson@cola.iges.org)
    • Igor Polyakov (igor@iarc.uaf.edu, ivp@gfdl.gov)
    • Claus Boening (cboening@ifm.uni-kiel.de)
    • Joachim Dengg (jdengg@ifm.uni-kiel.de)
    • Alistair Adcroft (adcroft@sea.mit.edu)
    • Sonya Legg (slegg@whoi.edu)
    • Eric Chassignet (eric@rsmas.miami.edu)
    • Tamay Ozgokmen (tamay@rsmas.miami.edu)

    DOME is currently seeking someone to fill the role of coordinator.

    Comparisons are taking place between isopycnal, geopotential and sigma coordinate models within the following, quasi-chronological framework of tests:

    • Idealized dense overflows.
      • .
    • Realistic Mediterranean Outflow and Denmark Straits scenarios.
    • Quasi Global simulations.

    In the case of the idealized overflow, we intend to conduct a series of tests for each model utilizing different horizontal and vertical resolutions, stratifications, slopes etc. This will clearly identify the strengths and weaknesses of individual models in a framework which will minimize model to model differences and enable meaningful quantitative comparisons to be made.

    The components of each of the tests are designed to be conducted in house by each of the participating groups. In the case of the idealized overflows in particular, this will circumvent a traditional problem with regard to funding agencies, who want to see more applied results. Most importantly however, it will enable open participation in DOME now and in future years by the whole scientific community. All the relevant information pertaining to the configuration of the tests, quantitative performance measures etc., is being continually added to a rapidly growing technical report.

    Should you have any interest in DOME, whether it be simple curiosity, or whether you think you may wish to become involved, please download the working report, or simply contact R. Hallberg via email at rwh@gfdl.gov

    PS The continually updated working report referred to above is available as a gzipped color postscript file of uncompressed size 1.07 Mb, in letter format. It is 25 pages in length.