[Liwg-core] Do we want the Antarctica wetland-glacier fix in the JG-BG spinup?

Bill Sacks sacks at ucar.edu
Tue Dec 4 13:12:54 MST 2018


Based on discussion with Kate, Bill L, Gunter and Erik Kluzek: Our plan 
will be to use the fixed surface dataset when Kate restarts the JG-BG 
spinup.

Bill Sacks wrote on 12/4/18 11:05 AM:
> Thanks for those thoughts, Jeremy.
>
> For what it's worth, the decision at today's co-chairs meeting is that 
> we'll use the fixed surface datasets for all configurations starting 
> with the CESM2.1.1 code base. This means that even preindustrial and 
> historical runs with the CESM2.1.1 code base will use the fixed 
> surface dataset (and thus differ slightly from the official CMIP6 
> runs). However, we will not redo any of the already-completed runs 
> (PI-control, historical, or WACCM 1% and 4xCO2) with the bug fixed.
>
> Bill
>
> Jeremy Fyke wrote on 12/4/18 10:00 AM:
>> My two cents: it may be worthwhile to fix this if there is capacity to do so, because if it's not fixed, it could be a barrier to science exploring emergence of significant ~post-2050 Antarctic shelf surface melt in CMIP6/etc. runs..?
>>
>> Jeremy
>>
>> -----Original Message-----
>> From: Liwg-core [mailto:liwg-core-bounces at cgd.ucar.edu] On Behalf Of Bill Sacks
>> Sent: Tuesday, December 4, 2018 8:46 AM
>> To:<liwg-core at cgd.ucar.edu>  <liwg-core at cgd.ucar.edu>
>> Subject: [Liwg-core] Do we want the Antarctica wetland-glacier fix in the JG-BG spinup?
>>
>> Hi all,
>>
>> Kate raised this question to me this morning, and I didn't have an answer, so I thought I'd see what others think: As many of you know, a bug was found in the CLM surface dataset, in that Antarctica's ice shelves are treated as wetlands rather than glaciers. In preindustrial and present-day climates, this has little impact on the climate, since the land surfaces are snow covered (although there are some minor differences due to different physics of the two landcover types).
>> However, this can still have an impact on how easy it is to do some analysis of the runs.
>>
>> So: Do people feel it's worth changing the surface dataset to the fixed version? In principle this should be straightforward, though it will probably require some coordination between Kate and Erik to make sure that the right fixed version is used. This could be worth doing if people plan to use the JG-BG spinup output for Antarctica-focused analyses; if not, then my feeling is that it's probably not worth the time.
>>
>> Bill S
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