[MITgcm-support] Ice thickness category diagnostics

[Martin Losch]

The seaice-model is based on Hibler (1979). That means ice growth and melting is done in terms of one ice volume per grid cell (HEFF) and concentration (AREA). The mulitcategory stuff is only used to compute the heat flux. This makes sure that even for very thick ice, there is always a fraction (1/multidim = 1/7 by default) of relatively thin ice. The heat flux through this part of the ice is larger than for the rest, so that the heat flux averaged over all "categories" is non-zero even for very thick ice. This is not much more than a numerical trick, I believe. And yes, it means, that when ice grows, each "category" grows by the same fraction.

True multicategory ice with an evolving thickness distribution is in the pipeline, but I don't know the status of that.

Martin


On Feb 8, 2013, at 3:58 PM, David Huard <david.huard at gmail.com> wrote:

> Do you mean that when the model creates new ice, it creates a fixed fraction of ice in each category ? 15 % of thin ice, 15% of thick ice, etc ?
> 
> David
> 
> 
> On Fri, Feb 8, 2013 at 9:31 AM, Martin Losch <Martin.Losch at awi.de> wrote:
> On Feb 8, 2013, at 3:22 PM, David Huard <david.huard at gmail.com> wrote:
> 
> > What about the ice thickness categories ? Is there a way to get those fields individually rather than as a bulk concentration ?
> 
> Are you talking about the "SEAICE_MULTICATEGORY"-code? This code only assumes a fixed distribution (in fact, it is homogeneous) of "actual" ice thicknesses h (as opposed to HEFF = h*AREA), so there is no reason to save the extra fields.
> siTICES gives the surface temperatures for each category, if that is of any help.
> 
> Martin
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