[MITgcm-support] Supercooled waters in ice shelf cavities

[Martin Losch]

Hi Kayhan and Dimitris,

with SHELFICEuseGammaFrict = .TRUE., your uStar is limited from below by 1e-3 (ie. 1mm/sec, this is actually hardwired in the code), which will give you small but non-zero exchange coefficients, order 0.0027 (which is not so small after all), if I am not mistaken.

So with T = -100degC, the (freezing) heat flux at the interface should be also record breaking even though there’s no flow.

I would try to get rid of this grid cell, and any other hole like this in the ice-shelf topography (fill it).

Martin

> On 14. Aug 2025, at 14:57, Dimitris Menemenlis <dmenemenlis at gmail.com> wrote:
> 
> Dear Martin, Yoshi, and Jean-Michel, in working towards the llc8690 set-up, Kayhan Momeni and I ran into following problem, illustrated in the two attached figures.  The figures show North/South and East/West vertical sections of Theta in one of the cavities, beige is land and blue is ice shelf.  The grid cell circled in red (at top west end of the East/West section and middle top of the North/south section) reaches a temperature of close to -100 K — I think that must be a world record!
> 
> The model configuration that we use is documented here: https://github.com/MITgcm-contrib/llc_hires/tree/master/trillium/llc_1080
> Importantly we have enabled pkg/shellfice and pkg/frazil
> 
> What I think is happening is that this location does not see any circulation because it is surrounded by land or ice shelf so negative heat anomaly from neighboring deeper cavity cells, mediated through pkg/frazil, rise to the surface and get stuck in that “inverted well" grid cell, which does not interact with the ice because u* is zero.
> 
> Have you ever ran across this situation and how did you solve (or suggest that Kayhan and I solve)?
> 
> Cheers, Kayhan and Dimitris
> 
> 
> <EastWestVerticalSection.jpeg>
> 
> <NorthSouthVerticalSection.jpeg>
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