[MITgcm-support] Ice not Moving when Resolution is Very High

[Nils Hutter]

Hi Senja,

I think I observed similar behaviour in the idealised experiments I did some years ago. My setup was a 500x500km basin covered entirely with sea-ice (100% concentration, and 20 cm thickness). Ice drift was driven by storm systems passing over the domain. I simulated this set-up with varying horizontal grid spacing from 1km to 10km. To observe the same dynamical behaviour of the ice (first deformation of the ice and break up along the coast), I needed to reduce the ice strength P* in the 1km simulations significantly to achieve similar behaviour as in the 2.5km simulations. You can find a full descriptions of this phenomena and a suggestion how to scale the ice strength P* with varying resolution in my Master Thesis, Chapter 5.2: https://epic.awi.de/id/eprint/38870/1/Masterthesis_NHutter.pdf

If in your case the lake is completely covered with ice, you might observe something similar, and reducing the ice strength might help. Or do you initialize single floes surrounded by water that should be in free drift? In this case, varying ice strength would not make a difference.

Cheers,
Nils

—
Dr. Nils Hutter
Climate Dynamics

Alfred Wegener Institute
Helmholtz Centre for Polar and Marine Research
Bussestr. 24
D-27570 Bremerhaven
Germany

Phone: ++49(0)471-4831-2900
http://www.awi.de/en/about-us/organisation/staff/nils-hutter.html

On 15. Jan 2020, at 23:02, Senja Walberg <senja.w at gmail.com<mailto:senja.w at gmail.com>> wrote:

Hello,

I'm currently experimenting with using the SEAICE package to simulate lake ice. The domain I consider is hence very small compared to the global ocean and the size of my grid cells is able to be set even smaller than would conventionally be used with sea ice models.

A scaling test that I've conducted is to make a simple wind-forcing experiment, where a constant 6 m/s wind is applied to a 1m, area=1 floe, the dimensions of which scale with the resolution (all I'm doing is taking the same run and changing delx, dely).

What I've found is that when delx=1km, the ice moves easily and movement can be seen on a timescale of several minutes, and that this is also seen when delx=500m, but when I set delx yet smaller to be 100m and 20m no movement was seen at all in a reasonable span of time. I have some intuitive notion that smaller floes should accelerate more slowly, which may be wrong itself, but at some point even if the motion induced by the wind is small, the currents of the water should cause the ice to move. Instead, the initialized ice floes resemble static islands.

Is there something in the ice model that prevents it from scaling this low, or is there some parameter or flag that needs adjustment in my set-up?

Attached are my data.seaice and SEAICE_OPTIONS.h

Cheers,
Senja
<data.seaice><SEAICE_OPTIONS.h>_______________________________________________
MITgcm-support mailing list
MITgcm-support at mitgcm.org<mailto:MITgcm-support at mitgcm.org>
http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.mitgcm.org/pipermail/mitgcm-support/attachments/20200117/7d8674a1/attachment-0001.html>