Turn use_excess_ice_streams off for clm6_0 cases with spunup finidat files

[ekluzek]

Now that we have a long history of doing clm6_0 simulations with excess ice on, we can turn off the stream files for the any cases that have finidat files to startup from.

@mvdebolskiy this is from my understanding of how excess ice works. You should ONLY use the streams file when you don't have excess ice on the IC file. In cases where you do have excess ice -- you should always use it from there. And this is also true for spinup cases like 1850 compsets. The reason is that there could be a few gridcells where excess ice melts from the previous simulation, and if that's the case you want that excess ice to remain melted.

I'm sure about this for 2000, 2010 and HIST compsets, I'm just less sure about 1850, since those cases run for hundreds to thousands of years. So in those spinup cases it's more likely that some random anomalous warming could happen and melt excess ice that maybe should have?

[mvdebolskiy]

@ekluzek I don't think the warming in 1850 is an issue. The uncertainty in the distribution that is used in streams is high.
Is your suggestion make exice_streams to be only read during coldstart and prohibit it to be read on start in hybrib/from finidat with phys=clm6_0?

[ekluzek]

@ekluzek I don't think the warming in 1850 is an issue. The uncertainty in the distribution that is used in streams is high. Is your suggestion make exice_streams to be only read during coldstart and prohibit it to be read on start in hybrib/from finidat with phys=clm6_0?

I don't want to prohibit streams from being used. But, I'd like to have it expect that excess ice is on the finidat file, if a finidat file is set for clm6_0. So it would use streams under a cold start, and for older physics finidat files that don't have excess ice on. If the finidat file doesn't have excess ice on it -- the simulation will fail at runtime in initialization -- and it will tell you to turn the excess ice streams on. So not a big deal.

So by default for a non-coldstart clm6_0 physics case it wouldn't use excess ice streams -- but the user could turn it on if they wanted to. If you ask for the streams to be used -- it'll overwrite what it read in on the restart file with the streams. So it seems like it would be best to trust what's on the restart file rather than the streams.

This seems to me to be the best way to go if I'm right -- that we should trust excess ice on restart files over the excess ice streams. When we first added in excess ice we didn't have finidat files with excess ice on it. But, now all of the files we've been creating for over a year have it on.