Open adele-morrison opened 1 year ago
Here is the surface freshwater budget components integrated over the shelf (ht < 1000m) in the last year (annual averaged):
Salt fluxes from sea-ice (which I believe is accounted in the "melt" term) and salinity restoration are converted to equivalent freshwater by:
FW_ice = 1000 x sfc_salt_flux_ice/SSS FW_restore = 1000 x sfc_salt_flux_restore/SSS
The main differences are (1) reduction of the river/runoff term and (2) increase of the sea-ice salinification net effect in the Basal and ICB runs compared to the control.
The restoring term is smaller than other terms (by 2 orders of magnitude) but also changes across experiments:
And here some annual average maps:
1) net surface fw flux (pme_river):
2) surface fw flux due to sea-ice (melt):
Some maps for the salt flux converted to FW (note the different colorbar limits in comparison with previous post):
salt flux due to sea ice converted to FWF:
same but due to salinity restoring:
I'm not sure I understand what's going on here @fabiobdias. Did you include the new freshwater input from the basal and iceberg terms? These aren't included in river
by the looks of the above plot. What are the diagnostic names to include the freshwater from basal and icebergs @pedrocol?
Also is melt
= wfiform
+ wfimelt
? The melt
diagnostic is incorrect.
The variable names are:
No, I haven’t taken those terms into account – thanks Pedro. I will re-do these and double-check the melt term.
From: Pedro @.> Date: Thursday, 2 November 2023 at 10:31 am To: pedrocol/basal_mom5-collaborative-project @.> Cc: Fabio Boeira Dias @.>, Mention @.> Subject: Re: [pedrocol/basal_mom5-collaborative-project] Freshwater budget (Issue #68)
The variable names are:
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Salt fluxes from sea-ice (which I believe is accounted in the "melt" term) and salinity restoration are converted to equivalent freshwater by:
FW_ice = 1000 x sfc_salt_flux_ice/SSS FW_restore = 1000 x sfc_salt_flux_restore/SSS
I think there are 2 problems here:
the FW flux associated with sea ice melt should be calculated using the fixed bulk salinity of sea ice (ice_salt_concentration
= 0.005 kg salt / kg ice), not SSS
Is the salinity restoring done as a salt flux (salt_restore_as_salt_flux
= true)? If so I don't think it makes sense to convert salinity restoring to a FW flux, as there is no associated FW change.
See sec 3.5.2, 3.5.3 of the draft tech report.
To possibly clarify point 2: the salinity changes under restoring are purely due to salt mass flux, not FW mass flux. You can only form a budget with extensive variables like salt mass and water mass, not intensive variables like salinity.
Updated surface freshwater budget figure. Some notes:
Also, I'm still including the converted FWF from sfc_salt_flux_ice and sfc_salt_flux_restore terms, but following Andrew comments above we should remove the restore from the final figure. Is the sfc_salt_flux_ice already included in the wfiform/wfimelt terms as well? If so, we could remove that too.
Just want to add a note here as I got a bit confused when closing the budget. The pme_net
and pme_river
terms do NOT include the additional basal/iceberg fluxes (basal_fwflx2d
and icb_fwflx2d
, in the same way they aren't included in the river
output). This changes the values of the net FWF (pme_river in the plot above). New corrected plot below.
Recapping, we have:
NET = pme_river + basal_fwflx2d + icb_fwflx2d
MELT = wfiform + wfimelt
PME = pme_net - MELT
RIVER = river + basal_fwflx2d + icb_fwflx2d
considering SSSi = 1/0.005 as the "fixed bulk salinity of sea ice (ice_salt_concentration = 0.005 kg salt / kg ice)", and SSS the model surface salinity:
FW_ICE = -sfc_salt_flux_ice*1000)/SSSi
FW_RESTORE = -(sfc_salt_flux_restore*1000)/SSS
The surface FW budget are given by:
NET = PME + RIVER + MELT
(so leaving FW_ICE/RESTORE out of the FW budget as Andrew suggested).
In summary, for models using this depth distributed basal fluxes and/or iceberg fluxes, the basal_fwflx2d
and icb_fwflx2d
needs to be summed to the pme_net
, pme_river
and river
diagnostics. Not sure if we should do this internally in MOM5 to be consistent?
New fig below - I'll be adding this and the SHF budget in the overleaf next:
Hi Fabio, I'm not sure I'm following, the code accounts for basal and icb fluxes for the zero_net_water_coupler (line 4081 in /home/552/pc5520/access-om2/src/mom/src/mom5/ocean_core/ocean_sbc.F90)
pme_river(i,j) = pme(i,j) + river(i,j) + basal(i,j) + icb(i,j) - melt(i,j) - wrk1_2d(i,j)
In this way, when splitting runoff (river) in basal+icb, the rest of the fields remain unchanged.
I did a mass balance and it was ok, would you mind sharing your jupyter notebook?
Hmm... now I got confused. Are you saying the basal_fwflx2d/icb_fwflx2d
aren't included in the river
but they are in pme_river
?
Following my analyses, I think it's either not included in both (as my note above), or it's already included in both. I believe it isn't included in both as river
in the control only matches with the total runoff from Basal_gade and NoBasal_gade experiments if I add the basal_fwflx2d
to river
. That aligns with Adele's suggestion from above:
I'm not sure I understand what's going on here @fabiobdias. Did you include the new freshwater input from the basal and iceberg terms? These aren't included in
river
by the looks of the above plot. What are the diagnostic names to include the freshwater from basal and icebergs @pedrocol?
If I added basal_fwflx2d
(and icb_fwflx2d
) to river
but don't do it for pme_river
, I can't close the budget.
river
in the ICB expt is zero, so basal_fwflx2d+icb_fwflx2d
accounts for all runoff (which is less than the total runoff in other experiments and that contributes to a larger difference in the NET FWF relative to control compared to Basal_gade). I'm not sure this is something we should expect.
I'm going to push the FW (and heat) budget scripts. I have also a spreadsheet with the shelf-integrated values that I can share if you want (these values are all printed in the notebook).
basal and icb arrays are not included in river:
river(i,j) = runoff(i,j) + calving(i,j); where calving = 0.0 and runoff(i,j) = 0.0, but runoff was previously split in basal(i,j) and icb(i,j). So, river(i,j) + basal(i,j) + icb(i,j) remain unchanged, as well as pme_river.
Indeed, river is expected to be zero in the ICB experiment.
I think the problem comes from the calculation region, you are calculating the quantities on-shelf only, and the ICB field is also present further away.
I've just re-done this but integrated over the whole domain (up to 60S or so), but I still think pme_river
doesn't include basal_fwflx2d+icb_fwflx2d
fluxes.
Even integrated over the whole domain (S.O.), the imbalance in the NET - (PME+RIVER+SEA-ICE) still exists. I need to add basal_fwflx2d+icb_fwflx2d
to close the surface FW budget (see table and figs below).
For the ICB experiment, what you said holds when I integrated for the whole SO (not only cont. shelf)–the ICB total river flux (river+basal_fwflx2d+icb_fwflx2d
) gets pretty close to the river in the control run (or river+basal_fwflx2d
in the Basal_gade).
The integrated values are: <html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:x="urn:schemas-microsoft-com:office:excel" xmlns="http://www.w3.org/TR/REC-html40">
| pme_river | pme_net - melt | river + basal + icb | | melt | | -- | -- | -- | -- | -- | -- | -- | -- 1E8 (kg s-1) | NET | PME | RUNOFF | basal/icb 2dflx | SEA-ICE | pme_net +river + basal + icb | minus (basal+icb) CTRL | 3.55587328 | 1.36628928 | 0.87460016 | 0 | 1.31498392 | 3.55587336 | BG | 3.04362976 | 1.35479456 | 0.87459888 | 0.45816592 | 1.27240208 | 3.50179552 | 3.0436296 ICB | 2.60107904 | 1.34355968 | 0.87818384 | 0.87818384 | 1.25751928 | 3.4792628 | 2.60107896
It would be great to repeat this budget analysis we did for the old simulations.
How does the freshwater budget, and its components, integrated over the shelf change? There will be changes due to the input salinity of the basal melt, changing salinity restoring, changing sea ice formation/melt, other air-sea FW fluxes (evap), and cross-slope transports of fresh/salty waters.
Old issue is here.