SWMT shifts to lighter densities in MOM6-01

[schmidt-christina]

I calculated the SWMT in six different 1/10th MOM6 configurations:

• panant-01-zstar-v13: 1/10th panantarctic zstar run with ACCESS-OM2-01 year 200 IC + BF
• panant-01-hycom1-v13: 1/10th panantarctic hybrid run with ACCESS-OM2-01 year 200 IC + BF
• panant-01-zstar-ACCESSyr2: 1/10th panantarctic zstar run with ACCESS-OM2-01 year 2 IC + BF
• global-01-v1: 1/10th global zstar run (version 1) with ACCESS-OM2-01 year 200 IC
• global-01-v2: 1/10th global zstar run (version 2) with ACCESS-OM2-01 year 2 IC
• global-01-v3: 1/10th global hybrid run (version 3) with ACCESS-OM2-01 year 2 IC

The peak of the mean (1996-2000) SWMT in each of the 4 formation regions occurs at different densities with runs that start from year 200 of ACCESS-OM2-01 being denser (blue, orange, red line) and runs starting from year 2 of ACCESS-OM2-01 (i.e. close to WOA observations) being lighter. This is especially visible in the Weddell Sea.

The peak of the SWMT shifts to lighter densities each year in the runs that start from ACCESS-OM2-01 year 2 in all regions and especially in the Ross Sea.

In runs starting from ACCESS-OM2-01 year 200 the density of the peak SWMT isn't shifting to lighter densities as much and also slower (note that the 2nd Plot with panant-01-zstar-v13 includes 46 years more)

A timeries of the SWMT for a density at a mean (1991-2012) transport of 70% of the maximum transport (orange line) for panant-01-zstar-ACCESSyr2 shows that after 10 years the SWMT dropped below 0.5 Sv from around 2 Sv in the Weddell/Ross Seas.

I didn't see a difference between vertical coordinates, or whether it was global or panantarctic. Plots for all of the runs are here: https://github.com/schmidt-christina/mom6_comparison/blob/main/SWMT_Plots.ipynb

[schmidt-christina]

We were wondering whether that had something to do with the initial stratification, so I looked at bottom T/S/rho and compared panant-01-zstar-v13 and panant-01-zstar-ACCESSyr2.

All plots and more detailed text are here: https://github.com/schmidt-christina/mom6_comparison/blob/main/Shelf_properties_Plots.ipynb

Initial temperatures don't differ much between panant-01-zstar-v13 and panant-01-zstar-ACCESSyr2 in the DSW formation regions, but it's up to 2°C warmer in the Amundsen/Bellingshausen Sea (not shown here).

Salinity: The initial conditions in the Weddell Sea are fresher (up to 0.2 psu) in panant-01-zstar-v13 compared to panant-01-zstar-ACCESSyr2. But this reverses with panant-01-zstar-v13 being saltier everywhere on the shelf after 10 years. The Weddell Sea gets saltier in panant-01-zstar-v13 and fresher in panant-01-zstar-ACCESS-yr2. The Amundsen Sea gets saltier and the Ross Sea fresher in both runs, but the magnitude of the freshening is slightly stronger in panant-01-zstar-ACCESSyr2, so that panant-01-zstar-v13 is still saltier.

Overall, it’s getting lighter everywhere on the Antarctic shelf in panant-01-zstar-ACCESS-yr2, especially in the Ross Sea.

Horizontal mean density profiles in the Weddell and Ross Sea have mostly the same shape in both runs, panant-01-zstar-ACCESS-yr2 is often lighter (with a constant offset over the whole water column compared to panant-01-zstar-v13). But it is not necessarily like that from the start, it often gets lighter over time as the SWMT shifts to lighter densities.

[adele-morrison]

Amazing analysis, thanks @schmidt-christina! Rather unexpected, because we have the same atmospheric forcing, same vertical grid and same horizontal resolution / bathymetry as ACCESS-OM2-01.

@AndyHoggANU suggested we could try playing around with the boundary layer vertical mixing schemes. I'll try to get some panan-01 test cases going today with different mixing schemes / parameters.

[AndyHoggANU]

Yeah, I agree this is a very nice analysis. I'm also very interested in seeing what we get out of the 1/20° case. @schmidt-christina - if you have time to look at your current 1/20° simulation before our Monday morning meeting that would be helpful!

[schmidt-christina]

I have 5 years of the 1/20th run now. So far it doesn't look too bad, there is certainly not the same shift that I can see already in the first 5 years in the 1/10th run with same IC + BC etc. But as I only have five years yet, I would still be a bit cautious. Also the SWMT is quite weak in the Weddell Sea.

Plot below is the panant-01-zstar-ACCESS-yr2 with the shift visible already in the first 5 years for comparison:

[adele-morrison]

That’s good news! Did you decide at the meeting today to run longer? If so, has anyone checked what the density binning on vmo and umo is like? Might be good to double check the diagnostic list, so we don’t have to rerun 10 years (perhaps you already did this at the meeting today). Do we have x and y heat flux diagnostics switched on too?

On Mon, Apr 17, 2023 at 8:36 AM, Christina Schmidt @.***> wrote:

I have 5 years of the 1/20th run now. So far it doesn't look too bad, there is certainly not the same shift that I can see already in the first 5 years in the 1/10th run with same IC + BC etc. But as I only have five years yet, I would still be a bit cautious. Also the SWMT is quite weak in the Weddell Sea.

[image: image] https://user-images.githubusercontent.com/38216156/232346051-52918744-5362-497a-b61b-ed8c96901109.png

Plot below is the panant-01-zstar-ACCESS-yr2 with the shift visible already in the first 5 years for comparison:

[image: image] https://user-images.githubusercontent.com/38216156/232346063-d7b7dc9c-d4ad-463c-85ba-6cdeb1f76011.png

— Reply to this email directly, view it on GitHub https://github.com/COSIMA/mom6-panan/issues/40#issuecomment-1510506826, or unsubscribe https://github.com/notifications/unsubscribe-auth/ACA44UZCFUHRWX3DV3FSQ5TXBRYABANCNFSM6AAAAAAW4S7JMY . You are receiving this because you commented.Message ID: @.***>

[schmidt-christina]

Yes, we decided to run another 5 years and it's running atm. We briefly looked at the density binning, but decided that I would look at it in more detail. So maybe I can look at it first thing tomorrow morning and pause the run in the meantime?

What do you mean by "x and y heat flux diagnostics"?

[adele-morrison]

I wouldn't bother pausing, just keep running and see if you can check the density binning as soon as you can.

Zonal and meridional heat fluxes, I'm not sure what they're called in MOM6. WIlton, do you know, or could you check?

On Mon, 17 Apr 2023 at 16:04, Christina Schmidt @.***> wrote:

Yes, we decided to run another 5 years and it's running atm. We briefly looked at the density binning, but decided that I would look at it in more detail. So maybe I can look at it first thing tomorrow morning and pause the run in the meantime?

What do you mean by "x and y heat flux diagnostics"?

— Reply to this email directly, view it on GitHub https://github.com/COSIMA/mom6-panan/issues/40#issuecomment-1510754789, or unsubscribe https://github.com/notifications/unsubscribe-auth/ACA44U6QH6QSJMULF7WNRQ3XBTMP3ANCNFSM6AAAAAAW4S7JMY . You are receiving this because you commented.Message ID: @.***>

[schmidt-christina]

I found this variable, is that the right one @adele157 @willaguiar ?

T_advection_xy"  [Unused]
    ! modules: {ocean_model,ocean_model_z,ocean_model_rho2,ocean_model_d2,ocean_model_z_d2,ocean_model_rho2_d2}
    ! long_name: Horizontal convergence of residual mean advective fluxes of heat
    ! units: W m-2
    ! cell_methods: xh:mean yh:mean zl:sum area:mean
    ! variants: {T_advection_xy,T_advection_xy_xyave}

[adele-morrison]

That’s 3D convergence, which would work if we only want circumpolar integrated heat fluxes. Better if we can have the actual x and y fluxes though.

On Tue, Apr 18, 2023 at 9:11 AM, Christina Schmidt @.***> wrote:

I found this variable, is that the right one @adele157 https://github.com/adele157 @willaguiar https://github.com/willaguiar ?

T_advection_xy" [Unused] ! modules: {ocean_model,ocean_model_z,ocean_model_rho2,ocean_model_d2,ocean_model_z_d2,ocean_model_rho2_d2} ! long_name: Horizontal convergence of residual mean advective fluxes of heat ! units: W m-2 ! cell_methods: xh:mean yh:mean zl:sum area:mean ! variants: {T_advection_xy,T_advection_xy_xyave}

— Reply to this email directly, view it on GitHub https://github.com/COSIMA/mom6-panan/issues/40#issuecomment-1512215880, or unsubscribe https://github.com/notifications/unsubscribe-auth/ACA44U5LH4REGSTZ5IKNOETXBXEZPANCNFSM6AAAAAAW4S7JMY . You are receiving this because you were mentioned.Message ID: @.***>

[willaguiar]

I found this variable, is that the right one @adele157 @willaguiar ?

T_advection_xy"  [Unused]
    ! modules: {ocean_model,ocean_model_z,ocean_model_rho2,ocean_model_d2,ocean_model_z_d2,ocean_model_rho2_d2}
    ! long_name: Horizontal convergence of residual mean advective fluxes of heat
    ! units: W m-2
    ! cell_methods: xh:mean yh:mean zl:sum area:mean
    ! variants: {T_advection_xy,T_advection_xy_xyave}

I believe the fields we want are T_adx, and T_ady

[willaguiar]

I found this variable, is that the right one @adele157 @willaguiar ?

T_advection_xy"  [Unused]
    ! modules: {ocean_model,ocean_model_z,ocean_model_rho2,ocean_model_d2,ocean_model_z_d2,ocean_model_rho2_d2}
    ! long_name: Horizontal convergence of residual mean advective fluxes of heat
    ! units: W m-2
    ! cell_methods: xh:mean yh:mean zl:sum area:mean
    ! variants: {T_advection_xy,T_advection_xy_xyave}

I believe the fields we want are T_adx, and T_ady

 "ocean_model_z","T_adx",        "T_adx",            "ocean_annual_z",     "all", "mean", "none",2
 "ocean_model_z","T_ady",        "T_ady",            "ocean_annual_z",     "all", "mean", "none",2

from: https://github.com/NOAA-GFDL/MOM6-examples/blob/dev/gfdl/ice_ocean_SIS2/OM4_025/diag_table.MOM6

[adele-morrison]

My tests in panan-01 of different surface boundary mixing schemes made zero difference (at least to these overturning diagnostics - I haven't checked SWMT). I started from the orange config and:

1. Used a different set of options in the EPBL scheme (green),
2. Switched off EPBL and turned on KPP (red),
3. Same as for 2, but I also switched on the cvmix convective instability parameterisation (purple).

[adele-morrison]

The same information, but now with a much better diagnostic - cross 1000m isobath transport (thanks to @schmidt-christina for working on the code):

We haven't made a contour for the 1/20th run yet, but would be good to compare that also! And maybe panant-01-zstar-v13 would recover if we ran for longer?

[adele-morrison]

Turns out we don't have salinity restoring turned on in any of the panan configs. This is quite likely the problem!

[adele-morrison]

Restoring doesn't help. :(

This is using the same restoring file as ACCESS-OM2-01 with the same piston velocity and I've checked it's actually doing something.

[AndyHoggANU]

Hmm. Can you describe how you calculated the piston velocity?

[adele-morrison]

MOM6 uses piston velocity as the input parameter: (FLUXCONST_SALT = 0.11 ! [m day-1] The constant that relates the restoring surface salt fluxes to the relative surface anomalies (akin to a piston velocity). Note the non-MKS units.). I set this as 0.11 m/day.

This matches what we use in ACCESS-OM2-01: 1.1 m / 10 days.

[willaguiar]

Does MOM6 restores salinity under the ice as in MOM5 or has a different flag for it? Wondering if that could be it

[adele-morrison]

Yes, it also has an option to turn off restoring under ice. I opted to do exactly what we do in ACCESS (restore under ice).

On Thu, 27 Apr 2023 at 17:02, Wilton Aguiar @.***> wrote:

Does MOM6 restores salinity under the ice as in MOM5 or has a different flag for it? Wondering if that could be it

— Reply to this email directly, view it on GitHub https://github.com/COSIMA/mom6-panan/issues/40#issuecomment-1524914310, or unsubscribe https://github.com/notifications/unsubscribe-auth/ACA44UZWDWJQ4MSRKKCVLUDXDIKZDANCNFSM6AAAAAAW4S7JMY . You are receiving this because you were mentioned.Message ID: @.***>

[adele-morrison]

Poring through MOM6_parameter_doc.all, I noticed:

• We have DO_RIVERMIX = False (same as OM4). For ACCESS-OM2 we also don't mix, but we do have a 40m insertion thickness. I can't see any option for vertical depth to insert river input over in MOM6. Is it all going in to the surface layer? Might result in really stratified waters around the Antarctic coast?
• [I don't think this is important at all here, but just noting that I don't think we have any vertical penetration of shortwave. Might want to fix this for ACCESS-OM3.]

[AndyHoggANU]

So, try a run with river mix?

[adele-morrison]

Yep can do.

On Thu, 27 Apr 2023 at 21:20, Andy Hogg @.***> wrote:

So, try a run with river mix?

— Reply to this email directly, view it on GitHub https://github.com/COSIMA/mom6-panan/issues/40#issuecomment-1525514215, or unsubscribe https://github.com/notifications/unsubscribe-auth/ACA44U6APKYQDFNGI662SM3XDJI6LANCNFSM6AAAAAAW4S7JMY . You are receiving this because you were mentioned.Message ID: @.***>

[adele-morrison]

Plan from this morning's meeting (feel free to edit this comment to add your name to any of these or to add more suggestions):

1. More diagnostic analysis of panan vs ACCESS-OM2-01 spinup:

• Add ACCESS-OM2-01 to DSW export plot. Is it steady in the first 10 years? Wilton
• Add 1/20th to DSW export plot. Christina
• Look at different density thresholds for DSW export time series. Is the DSW still there just at lighter densities? Or does export stop? Christina
• Time series of T / S / rho (surface and bottom), MLD, sea ice, integrated over the continental shelf. Christina
• Look at sea ice melt/salt flux terms (need to switch on more diags, or just look at net freshwater flux for now (wfo) - time series, spatial pattern, etc. Fabio

Names of experiments to compare for the above analysis:

1. ACCESS-OM2-01 RYF: 01deg_jra55v13_ryf9091.
2. Original 1/10th panan (with year ~200 ACCESS at northern boundary and init. cond.): panant-01-zstar-v13.
3. Updated 1/10th panan (with year 2 ACCESS at northern boundary and init. cond.): panant-01-zstar-ACCESSyr2
4. Updated 1/20th panan (with year 2 ACCESS at northern boundary and init. cond.) NOTE NOT ON IK11: /scratch/e14/cs6673/mom6/archive/panan_005deg_jra55_ryf. This isn't in the main database, but is in this database: /g/data/e14/cs6673/mom6_comparison/Python_scripts/panan_005deg_jra55_ryf.db.

2. More detailed look at salinity restoring files. Salinity restoring using WOA data did not help DSW formation. Is this because WOA salinity is way too fresh in winter? Compare maps of WOA salinity restoring file (/g/data/ik11/inputs/mom6/panan/01deg/20230404/salt_restore.nc), ACCESS-OM2-01 surface salinity, and surface salinity from the Pauthenet et al. 2021 climatology (/g/data/ik11/observations/Southern_Ocean_Climatology_PauthenetETAL2021/TS_Climato_Antarctic60S.nc), focusing on winter months in particular. Perhaps if we have a surface salinity field that would aid DSW production (i.e. high salinity over shelf in winter), we could do another test with updated salinity restoring file and higher piston velocity or higher max allowed salinity difference.

3. Check input and parameter files for any anomalies.

• /g/data/ik11/outputs/mom6-panan/panant-01-zstar-ACCESSyr2/output000/MOM_parameter_doc.all
• /g/data/ik11/outputs/mom6-panan/panant-01-zstar-ACCESSyr2/output000/SIS_parameter_doc.all There are many parameters in here that I'm not sure how they compare to ACCESS-OM2, because I'm not sure what the CICE names mean. @aekiss could you take a look please?
• https://github.com/COSIMA/mom6-panan/blob/panan-01-zstar-run/input.nml

4. We noticed that RHO_OCEAN = 1030 in SIS_input, but RHO_0 = 1035.0 in MOM_input. Also, SEA_ICE_MEAN_DENSITY = 900.0 in MOM_input, but RHO_ICE = 905.0 in SIS_input. Does this matter? Could do a test if we think this is important.

5. Salt in sea ice. I also noticed that we have ICE_BULK_SALINITY = 0.0 (The fixed bulk salinity of sea ice.) and ICE_RELATIVE_SALINITY = 0.1 (The initial salinity of sea ice as a fraction of the salinity of the seawater from which it formed.) in SIS_input, and ICE_SALT_CONCENTRATION = 0.005 in MOM_input. Maybe we should try changing ICE_RELATIVE_SALINITY = 0.0 and ICE_BULK_SALINITY to match ICE_SALT_CONCENTRATION (noting that have different units)?

[adele-morrison]

Also the updated DSW export (across 1000m isobath) plot with restoring and rivermix cases:

I'm still running rivermix, but it's not looking hopeful. We can update this once we have 1/20th and ACCESS-OM2-01 data to compare also.

[schmidt-christina]

I created the 1000 m isobath for the 1/20 model and computed the cross 1000m isobath transport (green line). The offshore transport is higher in the 1/20th simulation compared to the 1/10th simulation. In agreement with the SWMT analysis it is stable for the first 5 years and then starts to slowly decline in year 1996+1997.

[schmidt-christina]

I also used a lighter density threshold to calculate the cross 1000 m isobath transport for all 1/10th simulations to see if we still produce DSW but at lighter densities. This is the case for the runs with year ~200 ACCESS at northern boundary and init. cond, but not when we use year 2 ACCESS BC + IC.

[AndyHoggANU]

Thanks @schmidt-christina -- very nice! Just to check: Is this 1/20° run starting from the same WOA restart as the ACCESSyr2 simulation? If yes, my feeling is that we have some cause for optimism that the 1/20° run will give us much better results than the 1/10° ... Is there an appetite (and spare SU) to restart the 1/20° with salinity restoring fixed, and any improvements we can make to the initial condition??

[adele-morrison]

Yes I think it’s definitely worth investigating the comparison of salinity restoring data choices suggested above. If we come up with better data we could do a quick test on the 1/10th first?

For initial conditions, WOA (which is pretty close to what the 1/20th is currently starting from) is pretty terrible on the shelf. Maybe worth comparing later years from ACCESS (I.e. v13 initial conditions) with WOA and Schmidtko bottom data to see why the v13 case is better?

On Thu, May 4, 2023 at 9:40 PM, Andy Hogg @.***> wrote:

Thanks @schmidt-christina https://github.com/schmidt-christina -- very nice! Just to check: Is this 1/20° run starting from the same WOA restart as the ACCESSyr2 simulation? If yes, my feeling is that we have some cause for optimism that the 1/20° run will give us much better results than the 1/10° ... Is there an appetite (and spare SU) to restart the 1/20° with salinity restoring fixed, and any improvements we can make to the initial condition??

— Reply to this email directly, view it on GitHub https://github.com/COSIMA/mom6-panan/issues/40#issuecomment-1534616469, or unsubscribe https://github.com/notifications/unsubscribe-auth/ACA44U2CRK7FCEYYMT4HTZDXEOIR5ANCNFSM6AAAAAAW4S7JMY . You are receiving this because you were mentioned.Message ID: @.***>

[schmidt-christina]

@AndyHoggANU: Yes, the IC + BC of the 1/20th run are identically to the ACCESSyr2 simulation

I would also prefer tests in the 1/10th first, as it takes quite long to run the 1/20th (and is expensive), we would probably need at least 8 years to see changes.

[adele-morrison]

Great, Christina, do you or someone else want to look at possible restoring data and put a 1/10th test on today, so we have something to look at on Monday? I'm still travelling, so can't do anything until next week.

On Fri, 5 May 2023 at 08:14, Christina Schmidt @.***> wrote:

@AndyHoggANU https://github.com/AndyHoggANU: Yes, the IC + BC of the 1/20th run are identically to the ACCESSyr2 simulation

I would also prefer tests in the 1/10th first, as it takes quite long to run the 1/20th (and is expensive), we would probably need at least 8 years to see changes.

— Reply to this email directly, view it on GitHub https://github.com/COSIMA/mom6-panan/issues/40#issuecomment-1535477979, or unsubscribe https://github.com/notifications/unsubscribe-auth/ACA44UYBDFNSWHB2IBKFGX3XEQS47ANCNFSM6AAAAAAW4S7JMY . You are receiving this because you were mentioned.Message ID: @.***>

[willaguiar]

I can put the 1/10th to run today with restoring salinity + change in sea ice parameters (Bulk salinity, density, etc) . Do we have the IC+BC for year 2 and 200 of ACCESS ready for the panan01 or do we create those ? If we have, what are their dirs?

[adele-morrison]

I'd suggest just running just the case with yr 2 boundary forcing to start, i.e. a copy of this case: /home/157/akm157/mom6/panan-01-zstar-yr2forcing/ All the required forcing is linked in there.

For the salinity restoring, have you compared winter maps of the 3 suggested salt data possibilities (ACCESS-OM2-01, Pauthenet, WOA) above to see which one will be best? Would be great to see those maps here (or a new issue perhaps - this one is getting long).

[willaguiar]

A simple comparison of summer (DJF) surface salinities between the Pauthernet, WOA and ACCESS ( in reference to WOA) below. Overall it seems that the Ross shelf has higher salinity values on the winter, but the opposite happens on Weddell. So if we restore towards Pauthernet we might have a better DSW formation in Ross, but get something worse in Weddell. ACCESS salinity field seem to be very similar to WOA, Maybe slightly saltier over the whole domain. Hello everyone. - I just realized that the previous figure was actually for DJF - summer. So here is a Winter surface salinity field anomalies between there restoring targets (JJA). Salinity anomalies are not as extreme - But Prydz bay looks alter, and easter Ross sea too.

If you want to see Salinity Anomalies in other seasons check here.

[aekiss]

I'm commenting on parameters here, as it seems a better spot for it https://github.com/COSIMA/mom6-panan/issues/42

[schmidt-christina]

[willaguiar]

Ok, some plots comparing the SSS in WOA salinity restoring target with final Surface_salt from 01deg_jra55v13_ryf9091. Comparison only for June, and winter. Notice I updated this previous comment cause it was showing summer instead of winter before. In the plots below it seems that output SSS in OM2 is fresher over the whole shelf in Jun than in WOA. But the Seasonal climatology plot for winter shows that the other months compensate somehow (Ross shelf gets saltier than WOA) that and that over 200 years winter salinities gradually increase to try to match the WOA target. I'm note sure if this increasing shelf salinity is the cause of DSW formation in the model tho, since DSW export is already relatively stable within the first 10 year in OM2-01.

Fig 1 = Salinity anomalies of OM2 output - WOA reference, for June, first 2 years of 01deg_jra55v13_ryf9091 and then year 201 and 202 Fig 2 = WOA, June salinity for reference Fig 3 = Average SSS South of the 1000m isobath (Shelf) and the same for the WOA target for reference. Fig 4. = Climatology of Seasonal Anomalies of SSS (OM2 output - WOA target), last 10 years of OM2 output

[schmidt-christina]

I don't really agree with your comment that output SSS in OM2 is fresher over the whole shelf in Jun than in WOA. It is certainly fresher very close to the coast, especially in the Weddell/Bellingshausen/Amundsen Seas, but that's not were we have strong SWMT. We normally have strong SWMT in the western Ross Sea and Adelie Coast, where the SSS in ACCESS-OM2 is a lot saltier , and in the western Weddell Sea (but not directly on the coast of the peninsula) and Prydz Bay, where the anomaly is not as strong, but it's still saltier in winter and spring.

[adele-morrison]

Thanks for plotting all these up @willaguiar! It's not as straightforward as I was thinking it might be. That really fresh band along the coast in ACCESS-OM2 might do weird things (make the shelf fresher) if we try restoring to that. But then again WOA is saltier, as Christina points out, directly over the DSW formation sites.

It's not clear to me what the best test would be. I'm thinking maybe another restoring run using WOA data, but ramp up the restoring parameters. For the last test I used: RESTORE_SALINITY = True ADJUST_NET_SRESTORE_TO_ZERO = True FLUXCONST_SALT = 0.11 SALT_RESTORE_FILE = "salt_restore.nc" SRESTORE_AS_SFLUX = True MAX_DELTA_SRESTORE = 0.5 MASK_SRESTORE_UNDER_ICE = False.

We could try as above, but increasing these to the OM4 values of: FLUXCONST_SALT = 0.1667 MAX_DELTA_SRESTORE = 5

To make this test a bit different to the last one, we could also use Pauthenet data south of 60S, patched to WOA north of that. It looks like Pauthenet is fairly different in the Amundsen / Bellingshausen / WAP, where we normally have large biases in ACCESS-OM2.

Any other opinions?

[adele-morrison]

Also for those who missed yesterday's meeting, our plan for the next week is as follows:

• Run 3 tests in the 1/10th panan to see if we can improve / understand the lack of DSW formation better:
  1. Hit the model harder with salinity restoring. Wilton to do this.
  2. Try some different initial conditions - so far the best DSW formation occurs with year 200 ACCESS-OM2-01 initial conditions, but these are pretty far from obs. We discussed MIMOC yesterday, but looking at this now, I see it doesn't include seal data, which is the largest data type on the shelf. Christina to do this.
  3. Update a bunch of the sea ice parameters, as outlined in this issue. Adele to do this.
• Continue to analyse the sea ice formation in more detail. Fabio to do this.

Hopefully one of these tests might give us some better DSW formation in the 1/10th. But if not, we will start the 1/40th run next week anyway.

[schmidt-christina]

I ran 10 years of panan-01 starting with initial conditions from "World ocean circulation experiment-argo global hydrographic climatology (WAGHC)" (Gouretski, 2018, Ocean Science). This climatology is saltier than WOA in the upper 40 m but fresher below, see here for a comparison between different climatologies.

This run is probably even worse compared to starting from ACCESSyr2 IC by just looking at the cross-1000m transport but it does confirm that the initial conditions indeed have quite a strong effect on the DSW formation and export.

[adele-morrison]

And results here for the test run with altered sea ice parameters (red line compared to equivalent control in orange):

I changed a bunch of sea ice parameters, and the shortwave penetration depth, as outlined in this issue. I guess - while not helpful for our purposes right now in setting up the 1/40th - this does indicate there is a strong sensitivity to sea ice parameters. Maybe if we tried to change those parameters individually we'd be able to identify which are the crucial ones and modify them to get more DSW formation rather than less as we've done here.

[willaguiar]

Added to Adeles plot here the case of restoring salinity with a stronger piston velocity (FLUXCONST_SALT = 0.1667 MAX_DELTA_SRESTORE = 5) and towards Pauthenet target salinities. It doesn't seem to change too much the final DSW export ( I checked to make sure it was using the new Salinity target, and it was). I guess it agrees with Adele's case of nothing changing when turning on salinity restore.

I checked the salinity over the shelf (south of 1000m isobath), and both SSS and SOBottom get lower and lower within 10 years (it maybe explains why we have less and less DSW?) , while in a OM2 run restored towards WOA (IC from WOA) salinities over the shelf get roughly stable around 5yrs (Added there for comparrison)

[adele-morrison]

Turns out we do get some improvement in DSW formation in the panan-01 when we use these salinity restoring settings (green line compared with control orange line):

RESTORE_SALINITY = True ADJUST_NET_SRESTORE_TO_ZERO = False FLUXCONST_SALT = 0.1667 SRESTORE_AS_SFLUX = True MAX_DELTA_SRESTORE = 5

Note we also used Pauthenet et al. 2021 SSS instead of WOA, but I don't think that was the important part. The crucial parts seem to be ADJUST_NET_SRESTORE_TO_ZERO = False and MAX_DELTA_SRESTORE = 5. I think with all the Antarctic runoff input at the surface next to the coast, we get a really extreme coastal freshening. Ramping up MAX_DELTA_SRESTORE = 5 (same as GFDL OM4 setting) acts to counteract the coastal freshening. Wilton's previous case had the same high settings, but without ADJUST_NET_SRESTORE_TO_ZERO = False and that did next to nothing, so I think with the global offset to zero the restoring, we must have ended up putting the wrong sign restoring flux in some places.

We're running with these settings for the panan production runs now.

[PaulSpence]

nice. that's starting to make sense :) P

On Fri, May 26, 2023 at 11:28 AM Adele Morrison @.***> wrote:

Turns out we do get some improvement in DSW formation in the panan-01 when we use these salinity restoring settings (green line compared with control orange line):

RESTORE_SALINITY = True ADJUST_NET_SRESTORE_TO_ZERO = False FLUXCONST_SALT = 0.1667 SRESTORE_AS_SFLUX = True MAX_DELTA_SRESTORE = 5 [image: Screen Shot 2023-05-26 at 11 41 28 am] https://user-images.githubusercontent.com/8506963/241111121-2252cd0f-9bf2-4e11-842e-5ab88dfa86e3.png

Note we also used Pauthenet et al. 2021 SSS instead of WOA, but I don't think that was the important part. The crucial parts seem to be ADJUST_NET_SRESTORE_TO_ZERO = False and MAX_DELTA_SRESTORE = 5. I think with all the Antarctic runoff input at the surface next to the coast, we get a really extreme coastal freshening. Ramping up MAX_DELTA_SRESTORE = 5 (same as GFDL OM4 setting) acts to counteract the coastal freshening. Wilton's previous case had the same high settings, but without ADJUST_NET_SRESTORE_TO_ZERO = False and that did next to nothing, so I think with the global offset to zero the restoring, we must have ended up putting the wrong sign restoring flux in some places.

We're running with these settings for the panan production runs now.

— Reply to this email directly, view it on GitHub https://github.com/COSIMA/mom6-panan/issues/40#issuecomment-1563764660, or unsubscribe https://github.com/notifications/unsubscribe-auth/ABSWJXFKFBEU4CD5W2GFOCLXIAPOFANCNFSM6AAAAAAW4S7JMY . You are receiving this because you are subscribed to this thread.Message ID: @.***>

-- I’m sending this message at a time that suits me. I don’t expect you to reply outside of your own work hours.

Paul Spence, Assoc. Prof. ARC Future Fellow Institute for Marine and Antarctic Studies https://www.imas.utas.edu.au/ University of Tasmania, Hobart, Australia https://paulspence.github.io/