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

Bette Otto-Bliesner ottobli at ucar.edu
Tue Dec 4 11:30:47 MST 2018

Hi Bill,

During the WACCM meeting yesterday, my impression is that they might want
to redo the WACCM 1% and 4xCO2 with the bug fixed if the CESM2(CAM6) 1% and
4xCO2 simulations with the bug fixed show a signal in or around Antarctica.


On Tue, Dec 4, 2018 at 6:05 PM Bill Sacks <sacks at ucar.edu> wrote:

> 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 <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> <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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[on collaborative leave at University of Leeds until 30 April 2019]

Bette L. Otto-Bliesner
Deputy Director and Senior Scientist
Climate and Global Dynamics Laboratory

National Center for Atmospheric Research
1850 Table Mesa Drive
Boulder, Colorado 80305
Ph:   303-497-1723
Cell: 720-908-0206
Fax: 303-497-1348
Email: ottobli at ucar.edu
Web page: http://www.cgd.ucar.edu/ccr/ottobli
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