Question about Sea level

[susonic]

Dear ROMS Users,

I have a simple question.
Does ROMS calculate sea level variation with respect to the temperature variation?
If it does, would you point out where the code is?

Thanks in advance,

-Peter

[arango]

See CPP option VAR_RHO_2D in file step2d_LF_AM3.h which adds vertically integrated density to the pressure gradient formulation.

[susonic]

As far as I know, ROMS is a Bousnessq approximated model which the desnsity field is fixed.

But as Dr.Arango mentioned, the zeta in ROMS seems varying with respect to density variation.

How do I understand about the zeta in ROMS?

[susonic]

Maybe my question was too naive and also I did not understand the theory well.

So I change my question.
In Pacific basin, I ran ROMS for decadal order.
The forcing is derived from AR4 and AR5(IPCC).

After I finished the calculation, I saw the zeta in ROMS was becoming larger as time went by.
First case, I set closed condition for all lateral boundary.
And in second case, I gave open boundary with monthly climatology data.
I saw rising zeta, in both cases.

ROMS is Boussnesiq approximated model, so the heat expansion does not affect to sea level rise.
Then I was wondering the reason why the sea level is rising?
The heat flux calculated via bulk formulae and I restored SSS from AR4 and AR5 ocean model.
I did not give river foring.

Any answer would be appreciated.

Best,

-JH

[arango]

This is very simple. You are gaining volume and this is due to the open boundaries. You may plot the domain volume for your solution as a function of time. It seems that using climatology at the boundary is not working for you. Nowadays, we get boundary condition from global models. Imposing climatology at the open boundary requires a lot of tuning. It also depends where the open boundaries are located.

[susonic]

Hi Dr.Arango,

Thank you very much for your reply.
Domain averaged volume can get through the log file from ROMS, right?
I can't log in the computer for some reason, right now.
I will plot domain volume with a time series as soon as I reach there.

By the way, I also ran the model with same domain and boundary condition but different surface forcing.
This forcing is RCP 26 case and the zeta in ROMS shows low sea level rise compare to the other one(RCP85 case, AR5).
The domain averaged zeta shows similar trend with that in SST in both cases.

If ROMS is getting volume in both cases due to the boundaries, I'm wondering the reason why zeta is showing different trend under the same boundary condition?