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Using a spun-up ocean to initialize active ocean-ice (G compset) run

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Using a spun-up ocean to initialize active ocean-ice (G compset) run



I'm trying to set up an ocean-ice (G_1850_cam5) simulation with a spun-up ocean condition. It iis desired that the simulation essetnially be a restart from the spun up ocean-ice from a coupled simulation.

I read from the user's guide that I could use the 'spunup' suboption under a startup run type. However, in this case, it looks like the model only uses the ocean restart but not the ice. And the ice model has instability issues after several minutes of running (ERROR: remap transport: bad departure points).


My question is:

Can I set the run type to a hybrid run instead of a "spunup start up"?  This way the ocean model and the ice model will both restart from the previous run. What would be the difference between this hybrid run and a spun up startup?



Thanks very much in advance!




Hello there Hui,

I wonder if you got this problem resolveed. as I am also confused by a startup run with spunup ocean. I think if you use restaert from a spun-up model to do a hybrid run, then your ocen should start from a spunup status. But why the user's guide indicates that you need to do a startup run to let the ocean start from spun-up status.

Cheers, Alcide


Hi Alcide, 


I was also very confused by the description in the user's guide... I ended up choosing the hybrid run because it makes more sense to me.

The comment by the NCAR expert helps a lot.  Hope this can be useful to you too. 




Hi Hui,

Thanks a lot for the information. I also ended up with a hybrid run.

Cheers, Alcide


I definitely recommend you do not use the "startup/spunup" option. This option should only be used by experts who know exactly the implications of this choice. Very, very few people fall into this category. (Also note that the option was developed for fully coupled cases, not for G-type cases, for which the option makes even less sense).

Instead, use a "hybrid" case.  You could also use a "branch" case, although for most purposes the hybrid would be perfectly fine and is perhaps conceptually easier. 

You should initialize your new hybrid or branch case with ice and ocean restart files from the same case, and both those files should be from the same model time.



Great! Thanks for the reply. I ended up choosing the hybrid run, and the simulation finished without any issue. 


Thanks again, 



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