Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/gmd-2017-268
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Model evaluation paper
01 Nov 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Geoscientific Model Development (GMD).
Intercomparison of Antarctic ice shelf, ocean, and sea ice interactions simulated by two models
Kaitlin A. Naughten1,2,3, Katrin J. Meissner1,2, Benjamin K. Galton-Fenzi4,3, Matthew H. England1,2, Ralph Timmermann5, Hartmut H. Hellmer5, Tore Hattermann6,5, and Jens B. Debernard7 1Climate Change Research Centre, Level 4 Mathews Building, University of New South Wales, Sydney NSW 2052, Australia
2ARC Centre of Excellence for Climate System Science, Australia
3Antarctic Climate & Ecosystems Cooperative Research Centre, Private Bag 80, Hobart TAS 7001, Australia
4Australian Antarctic Division, 203 Channel Highway, Kingston TAS 7050, Australia
5Alfred Wegener Institut, Postfach 12 01 61, 27515 Bremerhaven, Germany
6Akvaplan-niva, P.O. Box 6606, Langnes, 9296 Tromsø, Norway
7Norwegian Meteorological Institute, P.O. Box 43, Blindern, N-0313 Oslo, Norway
Abstract. An increasing number of Southern Ocean models now include Antarctic ice shelf cavities, and simulate thermodynamics at the ice-shelf/ocean interface. This adds another level of complexity to Southern Ocean simulations, as ice shelves interact directly with the ocean and indirectly with sea ice. Here we present the first published model intercomparison and evaluation of present-day ocean/sea-ice/ice-shelf interactions, as simulated by two models: a circumpolar Antarctic configuration of MetROMS (ROMS: Regional Ocean Modelling System coupled to CICE: Community Ice CodE) and the global model FESOM (Finite Element Sea-ice/ice-shelf Ocean Model), where the latter is run at two different levels of horizontal resolution. From a circumpolar Antarctic perspective, we compare and evaluate simulated ice shelf basal melting and sub-ice shelf circulation, as well as sea ice properties and Southern Ocean water mass characteristics as they influence the sub-ice shelf processes. Despite their differing numerical methods, the two models produce broadly similar results, and share similar biases in many cases. Both models reproduce many key features of observations, but struggle to reproduce others, such as the high melt rates observed in the small warm-cavity ice shelves of the Amundsen and Bellingshausen Seas. Several differences in model design show a particular influence on the simulations. For example, FESOM's greater topographic smoothing can alter the geometry of some ice shelf cavities enough to affect their melt rates; this improves at higher resolution, since less smoothing is required. In the interior Southern Ocean, the vertical coordinate system affects the degree of water mass erosion due to spurious diapycnal mixing, with MetROMS' terrain-following coordinates leading to more erosion than FESOM's z-coordinates. Finally, increased horizontal resolution in FESOM leads to higher basal melt rates for small ice shelves, through a combination of stronger circulation and small-scale intrusions of warm water from offshore.

Citation: Naughten, K. A., Meissner, K. J., Galton-Fenzi, B. K., England, M. H., Timmermann, R., Hellmer, H. H., Hattermann, T., and Debernard, J. B.: Intercomparison of Antarctic ice shelf, ocean, and sea ice interactions simulated by two models, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2017-268, in review, 2017.
Kaitlin A. Naughten et al.
Kaitlin A. Naughten et al.
Kaitlin A. Naughten et al.

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Short summary
MetROMS and FESOM are two ocean/sea-ice models which resolve Antarctic ice shelf cavities and consider thermodynamics at the ice shelf base. We simulate the period 1992–2016 with both models, and with two options for resolution in FESOM, and compare output from the three simulations. Ice shelf melt rates, sub-ice shelf circulation, continental shelf water masses, and sea ice processes are compared and evaluated against available observations.
MetROMS and FESOM are two ocean/sea-ice models which resolve Antarctic ice shelf cavities and...
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