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<pre>Hi Martin and those interested in the sea-ice behaviour,</pre>
<pre>I just wanted to report back that playing with the defaults that Martin suggested indeed solved my problem.
I did one run, where I switched back the four new defaults,
</pre>
<pre class="moz-quote-pre" wrap="">SEAICEscaleSurfStress to .FALSE.
SEAICEaddSnowMass to .FALSE.
SEAICE_useMultDimSnow to .FALSE.
SEAICE_drag to 0.002
But I also tried to be less drastic and did a few runs changing only one of them at a time.
The two parameters that had the strongest effect are SEAICEscaleSurfStress and SEAICE_drag,
the others also lowered the maximum seaice_heff (in monitor_seaice*.nc) somewhat.
Cheers, Christoph
</pre>
<div class="moz-cite-prefix">Am 01.02.19 um 10:22 schrieb Martin
Losch:<br>
</div>
<blockquote type="cite"
cite="mid:8926A27B-9839-4D7A-BAC5-4D38A27C6F2E@awi.de">
<pre class="moz-quote-pre" wrap="">Hi Paul,
it’s a shame that you need to use these diffusivities. For the original advection scheme (2nd order central difference), this was necessary, but shouldn’t not be required when you use one of the flux limited schemes.
I found that in long runs turning of the replacement pressure (as Christoph does with SEAICEpressReplFac = 0.) usually avoids having too tick ice in individual corners along the coastline (See Kimmritz et al 2017 for an explanation). I am not saying that this is more physical than extra diffusion, but is probably affects the solution less away from these critical points.
The diffusion has changed long ago. I don’t think that that is Christoph’s problem.
Martin
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<pre class="moz-quote-pre" wrap="">On 31. Jan 2019, at 20:02, Holland, Paul R. <a class="moz-txt-link-rfc2396E" href="mailto:pahol@bas.ac.uk"><pahol@bas.ac.uk></a> wrote:
Hi Christoph
I have had trouble with excessively thick sea ice around coastlines also. The only thing I found that would touch it is ice diffusion, e.g.
SEAICEdiffKhHeff = 10.0,
SEAICEdiffKhSnow = 10.0,
SEAICEdiffKhArea = 10.0,
SEAICEdiffKhSalt = 10.0,
I don't think this is particularly physical, but it works for me! I tried changing all the ice rheology parameters and none of them solved this problem for me. Be careful with the values of diffusion though - high values caused blow-ups and undesirable results for me.
If I understand it correctly, in the old original version of the sea ice code there was a diffusivity somewhere deep in the code (parameter DIFF1), which went away at some point, so I think this is just compensating for that change. But I think this change may have happened before checkpoint 66f.
Others have found that ice shelf meltwater leads to very thick ice forming as well, but that seems to be a much more localised problem.
Perhaps Martin can comment on the above?
Cheers
Paul
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">Date: Thu, 31 Jan 2019 16:49:59 +0100
From: Martin Losch <a class="moz-txt-link-rfc2396E" href="mailto:Martin.Losch@awi.de"><Martin.Losch@awi.de></a>
To: MITgcm Support <a class="moz-txt-link-rfc2396E" href="mailto:mitgcm-support@mitgcm.org"><mitgcm-support@mitgcm.org></a>
Subject: Re: [MITgcm-support] changes in seaice default behaviour?
Message-ID: <a class="moz-txt-link-rfc2396E" href="mailto:0BE148AD-8580-420C-9D24-34C51EEA8E17@awi.de"><0BE148AD-8580-420C-9D24-34C51EEA8E17@awi.de></a>
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<pre class="moz-quote-pre" wrap="">
Hi Christoph,
here:
<a class="moz-txt-link-rfc2396E" href="https://github.com/MITgcm/MITgcm/issues/107"><https://github.com/MITgcm/MITgcm/issues/107></a>
you can see, what the new defaults are. I guess you can try to do override some of them:
SEAICEscaleSurfStress (was .FALSE. now .TRUE.)
SEAICEaddSnowMass (was .FALSE. now .TRUE.)
SEAICE_useMultDimSnow (was .FALSE. now .TRUE., this will make ice thicker)
SEAICE_drag (factor of two smaller now)
SEAICE_waterDrag (shouldn?t make too much of a difference, since you didn?t set it explicitly)
More precise comments in doc/tag-index
I?m afraid, that none of this seems to me to be a candidate for your problems (maybe scaleSurfStress).
Martin
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">On 31. Jan 2019, at 16:17, Christoph Voelker <a class="moz-txt-link-rfc2396E" href="mailto:christoph.voelker@awi.de"><christoph.voelker@awi.de></a> wrote:
Dear all,
I have problems in continuing a global ocean run for the last glacial maximum that I suspect are related to changes in the default behaviour of the seaice module in checkpoint 67d.
I used to run the model with the somewhat outdated version checkpoint 66f over 3000 years. Then I switched to the newer code version, recompiled and wanted to continue the run for another 1000 years or so. What then happens is that - without having changed anything in my data.seaice and SEAICE_OPTIONS.h - the model starts accumulating very thick ice around Antarctica; ice tends to build up to typical ice thicknesses of more that 15 m where I previously only had 2 m or so. Eventually the model crashes and I believe it has to do with seaice+snow reaching a thickness of more than 60m in a few points.
Can anyone perhaps tell me which of the new defaults in the seaice parameters might me responsible and suggest what I could change?
I must add to this that I run a scenario where I force the model with atmospheric output (temperature, winds etc) from a coupled ocean atmosphere climate model run for the last glacial, so I get rather cold air temperatures around Antarctica. For that reason my data.seaice has already a few settings to prevent a too strong seaice buildup:
# SEAICE parameters
&SEAICE_PARM01
SEAICEwriteState = .TRUE.,
SEAICE_initialHEFF = 0.0,
HO = 1.,
SEAICEuseFlooding = .true.,
SEAICEadvSnow = .true.,
SEAICEpressreplfac = 0.,
SEAICE_clipVelocities = .false.,
SEAICEadvScheme = 33,
SEAICE_no_slip = .false.,
# SEAICE_deltaTevp = 360.,
&
Cheers, Christoph
</pre>
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<pre class="moz-signature" cols="72">--
Christoph Voelker
Alfred Wegener Institute
Helmholtz Centre for Polar and Marine Research
Am Handelshafen 12
27570 Bremerhaven, Germany
e: <a class="moz-txt-link-abbreviated" href="mailto:Christoph.Voelker@awi.de">Christoph.Voelker@awi.de</a>
t: +49 471 4831 1848</pre>
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