[MITgcm-devel] max seaice thickness statement

[Fenty, Ian G (3244)]

JM, 

If I remember correctly, the reason the cap was removed was related to the the particular way capping was implemented. I believe that if ice in excess of the cap was discovered, the energy required to melt that ice was extracted from the ocean to conserve energy.  As a consequence of that particular formulation, seawater enthalpies in the grid cell with the excessively thick ice were forced to become negative relative to the freezing point.  Some fraction of that negative enthalpy caused  ice to form anew at the same location, another fraction was advected around, and the remaining fraction remained to drive ocean temperatures down and down to NaNland.. 

In my opinion, if one wishes to cap_heff (i.e., do a blantantly unphysical thing), the best thing to do is to acknowledge the inevitablity of a violation of energy conservation implied by the desired violations of ice thermodynamics and physics.  I suggest that one should assume that any ice reaching above the critical height is instantly destroyed by the local fauna polar bears (in the NH) and penguins (in the SH). Other fantasies about the final resting place of ice exceeding the cap are welcome, provided those fantasies cause the ice to completley vanish "into thin air" as it were.  

-Ian
 

On Feb 2, 2014, at 7:25 PM, Jean-Michel Campin wrote:

> Hi,
> 
> Anthony is doing LGM type of simulations with pkg/seaice, and send me the
> message below.
> 
> In my answer, I added this:
>> Regarding the option to cap the seaice thickness, it was there in older
>> version of pkg/seaice (prior to Dec i27, 2012, CPP-option "SEAICE_CAP_HEFF"
>> and using run-time parameter "MAX_HEFF") but this has been removed.
>> Will ask arround if there is a simple way to put it back.
>> I think that this option exist within pkg/thsice (run-time parameter "hiMax")
>> but you might not be willing to switch to a different thermodynamics
>> (I would understand).
> 
> So my question is: Is there is a simple way to put back the "SEAICE_CAP_HEFF" code/hack ?
> 
> Cheers,
> Jean-Michel
> 
> On Sun, Feb 02, 2014 at 10:59:30AM -0500, Anthony Coletti wrote:
>> HI Jean-Michel,
>> 
>> My name is Anthony.  We met at the ECCO meeting a few weeks ago.  I am
>> Alan Condron's student.  You told me to send you an email without going
>> through the list, so here I am!
>> 
>> Anywho,
>> 
>> I wanted to know what the new updated sea-ice thickness statement is in
>> regards to capping my seaice from growing any bigger.  I was using
>> MAX_HEFF in my data.seaice file however, it gave me an error saying that
>> the statement has been "retired"
>> 
>> The reason I want to cap my seaice is because I was getting the infamous
>> calc_r_star error where r*star < hFacmin.  The model seems to just blow
>> up.  To alleviate this issue, I increase hFacMin = 1., .  This seemed to
>> work for a few hundred years of integration but it eventually crashed
>> again with a similar error.  This time, it was complaining about my
>> hFacInf.  So, I decided to tweak hFacInf from hFacInf = 0.2, to hFacInf =
>> 0.01, which may be too small??  So far, it has gone through a few decades
>> of integration without a crash, but I am not sure if messing around with
>> hFac will have devastating consequences later.
>> 
>> I figured that if I cap my seaice growth, I wouldn't have a problem with
>> the free surface lowering down to the bathymetry (which seems to be the
>> culprit with the calc_r_star error.  Do you have any suggestions for these
>> errors as I try to equilibrate my integration?  Will capping the seaice
>> help with this error?
>> 
>> Thank you for your time!
>> 
>> Anthony
>> -- 
>> Anthony J. Coletti
>> Climate System Research Center
>> Department of Geosciences
>> University of Massachusetts-Amherst
>> paleoclimate.org
>> ajcolett at geo.umass.edu
>> http://blogs.umass.edu/ajcolett/
>> 
> 
> ----- End forwarded message -----
> 
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Ian Fenty
NASA Jet Propulsion Laboratory
tel: 818-393-1506;  cell: 508-498-4879, 
Email: Ian.Fenty at jpl dot nasa dot gov