Expand the Greenland glacier region to extend slightly beyond Greenland

[billsacks]

In discussing the changes I'm making for #423 with @gunterl and @Katetc , Gunter raised some concern about not having any SMB beyond the Greenland land area, if someone wanted to do a run that allows the formation of ice shelves around Greenland.

After some discussion, we agreed that best thing to do long-term is probably to do a slight expansion of the Greenland glacier region on CTSM's surface dataset to accommodate possible/likely ice shelf expansion. However, this needs to be done carefully to avoid including much additional land (like Ellesmere Island) in this mask. (If Ellesmere Island is treated the same as Greenland, it can generate ice runoff that, at least in the past, has resulted in problematic runaway sea ice growth.)

(An alternative would be to go back to having an extra region for this purpose, but our feeling was that that's a less good approach, given that there aren't any great combinations of glacier region behaviors that can be applied to that region besides those that are applied to Greenland itself, so it would make more sense just to expand the Greenland region rather than re-introducing a separate, small region.)

[ekluzek]

@billsacks this is something that needs to come into surface datasets correct? So is this a required part of the ctsm5.3.0 work? And if so how much of a delay might this be?

We are trying to get new spunup initial conditions ASAP before the Aug/31st "chill" deadline. So it makes a difference if this would need to be included in that spinup or not....

[billsacks]

Oh, sorry, I wasn't clear: this is a longer-term thing. We recognized that there is no way this can be done for ctsm5.3.0, so we're moving ahead with the already-discussed plan for ctsm5.3.0 and CESM3, and this will be an "eventually" thing, probably led by the LIWG.

[wwieder]

@billsacks we have this assigned to a CTSM5.4 milestone (end of Feb). Is this still a desired timeline, or would a CTSM6.0 timeline be more appropriate?

[billsacks]

I think this needs input from @gunterl and @Katetc as to the priority and whether either of them would have time to do it. @gunterl and @Katetc - I'm happy to be part of this discussion and any planning for how to do this, but I probably won't have time to lead this work myself.

[billsacks]

@wwieder and @ekluzek - to help inform this discussion: are there already plans to remake surface datasets for ctsm5.4 for other reasons?

[wwieder]

the 5.4 datasets are slated to be created when-ever CMIP7 data (namely land use time series) are available. We're seeing this as the 'final' land input dataset creating tag before the CLM6.0 release.