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CICE monotonicity error

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CICE monotonicity error

I'm running a CESM simulation with CO2 at 185 ppm CO2. I'm using CESM1.2.1 with CAM5 FV 2deg and POP2 1deg.

The simulation was started from an equilibrated ocean and has been running without problems for 5 centuries now. The climate over these 5 centuries is colder and equilibrated.

However, on year 506 I get the following error:

ERROR: ice remap transport: monotonicity error

What is the best way to diagnose what is going on?


A monotonicity error in the CICE model suggests something is going really wrong. This is sort of analagous to a CFL violation. Sometimes this can be overcome by increasing the sea ice dynamics timestep for a bit. That is, change xndt_dyn to 2. However, you should have a look at the CICE velocities and surface POP velocities as I suspect these are growing unrealistically large. It could also mean that the winds in CAM are getting very large. Also, are you getting sea ice very far equatorward?




Hi Dave, the surface velocities are not excessive, nor the equatorward ice extent. However, it is a climate with a lot more ice because of the reduced CO2 concentrations. I changed the timestep as you indicated and that allowed to avoid the "instability". The simulation is running again. Thanks for your help.

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