[MITgcm-devel] pkg seaice max ice height

[Martin Losch]

Hi Jeff, 
there is,
#define SEAICE_CAP_ICELOAD
and the ice load is limited to a maxing of (seaice_growth, around line 343)
      heffTooHeavy=drF(kSurface) / 5. _d 0 = 20% of the surface cell thickness
Ice can still grow thicker but will not affect the nonlinear surface any further.

More physically: I had some good experience with turning off the replacement pressure (there’s a manuscript Kimmritz et al, 2017, hopefully it will get through the review process soon, that describes some of the effects of doing so: <http://mitgcm.org/~mlosch/PRM_NoPRM_Kimmritzetal_R2.pdf>). In recent code there’s a flag called SEAICEpressReplFac, which you can set to 0. to turn off the replacement pressure. In older code you can replace the line where press = 2*Delta*zeta by press = press0 in seaice_calc_viscosities.F
Keep in mind, though, that the replacement pressure was introduced to avoid spurious motion of sea ice in the absence of external forcing: you ice will move just because of thickness gradients, which may or may not be physical. I am not sure, which problem I like better: “spurious" motion due thickness gradients (glacier move that way) without replacement pressure or very low resistence against compression in very thick ice with replacement pressure = 2*Delta*zeta = P*Delta/Delta_reg. In thick ice, drift get’s very small, also strain rates and hence Delta, Delta is regularized from below, e.g. default is Delta_reg=max(Delta,2e-9), so that P*Delta/Delta_reg -> 0 for Delta << 2.e-9 and you can compress ice “infinitely”.

I am curious to hear what you find, if you decide to remove replacement pressure.

Martin


> On 24 Mar 2017, at 17:10, Jeffery R Scott <jscott at mit.edu> wrote:
> 
> 
> Hi all,
> 
> At some point there was a max allowable seaice height (pkg seaice) controlled by MAX_HEFF that seems to have been retired 4 years ago.
> 
> I’m running a regional Arctic setup at 36km and the ice in the long inlet in Ellesmere Island, and other spots near the top of Greenland,
> are more or less growing unbounded ( 10-15m and counting, until my NLFS gags).  
> 
> Is there an easy (new) way to cap seaice thickness here, and/or anyone have any suggestions?
> 
> Thanks,
> Jeff
> 
> 
> 
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