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Modelling self-organization in ice streams

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Abstract:

The EISMINT II experiments revealed the tendency for idealized model ice sheets to produce spatially variable flow under certain uniform thermal, mass-balance and topographic boundary conditions. Warm, fast-flowing streams with enhanced creep were separated by zones of colder, slower flow. Similar but different spatial patterns of differentiated flow were produced by all authors. We present further experiments that explore the formation and function of such ice streams at higher modelled resolutions. These are explored by the use of flat, but stochastically rough (10 m amplitude) beds, idealized, parallel-sided model ice sheets and models of finer (12.5 and 5 km) resolutions. Ice streams self-organize irregularly, but with consistent typical spacings which vary with thermal and mass-balance boundary conditions. More radial features are produced at finer scales indicating a dependency on the grid resolution used although this is not linear; at finer resolutions streams occupy increasingly more gridcells. This variation in scale may be related to the finer resolution of the warm/cold streaming/non-streaming boundary. The numerical solution of the thermodynamic ice equation is also highly sensitive to the orthogonality of the model grid. A major deficiency is that the numerical solution appears to fail where the flow is parallel to the grid axes, suggesting that artificial diffusion in the numerical scheme helps to smooth streams lying across the axes directions. The inclusion of sliding produces fewer, more concentrated, flow features, but these also display a level of scale-dependent organization. The spatial arrangement of such streams adjusts in response to the global mass flux of the ice sheet between "warm" and "cold" flow end-members. The results point to a mechanism in which ice sheets respond to climate by altering the large-scale arrangement of their flow patterns.

Document Type: Research Article

DOI: http://dx.doi.org/10.3189/172756400781820561

Publication date: January 1, 2000

More about this publication?
  • The Annals of Glaciology is a peer-reviewed, thematic journal published 2 to 4 times a year by the International Glaciological Society (IGS). Publication frequency is determined and volume/issue numbers assigned by the IGS Council on a year-to-year basis and with a lead time of 3 to 4 years. The Annals of Glaciology is included in the ISI Science Citation Index from volume 50, number 50 onwards.

    Themes can be on any aspect of the study of snow and ice. Individual members can make a suggestion for a theme for an Annals issue to the Secretary General, who will forward it to the IGS Publications Committee. The IGS Publication Committee will make a recommendation for an individual themed Annals issue, together with a potential Annals Chief Editor for that issue, to IGS Council. The IGS Council will make the decision whether to proceed, taking into account the spread of topics and the overall capacity for publication of pages in Annals.

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