Expose include_rivers_and_icebergs kwarg instead of using the default

[navidcy]

Despite include_rivers_and_icebergs = false is the default, I think it's good idea to expose it so that it's obvious to anybody that they need to tweak this to include runoff and icebergs.

We might want to consider making include_rivers_and_icebergs = true the default at some point.

[glwagner]

We might want to consider making include_rivers_and_icebergs = true the default at some point.

Does it change the solution? The fluxes are incredibly weak.

[navidcy]

We might want to consider making include_rivers_and_icebergs = true the default at some point.

Does it change the solution? The fluxes are incredibly weak.

I haven't quantified the effect. There should be an effect near rivers. But their effect might not be apparent in short simulations. Given that I don't know atm I am also not suggesting we change the defaults.

This PR only means to expose to the users the keyword argument since one could be thinking that JRA55PrescribedAtmosphere by default would uses all the JRA55-do fields.

[taimoorsohail]

I think the only one that makes a substantial difference in the Amazon discharge, about 1 Sv. It's a visible signal in basin-scale integrals (zonal integrals of freshwater content in the Atlantic, for example). For this reason I think we should include it down the track...

[glwagner]

It's worth noting that we wouild also like ot move this to a "land" component for OceanSeaIceModel. These are properly understood as fluxes form a land component, not from an atmosphere component.

[navidcy]

It's worth noting that we wouild also like ot move this to a "land" component for OceanSeaIceModel. These are properly understood as fluxes form a land component, not from an atmosphere component.

That's a good point. These are not atmospheric-related fields...
I think the river and icebergs are not originally part of JRA55 reanalysis; they are only included in the JRE55-do (=drive ocean) version.

I'm merging since this PR doesn't change anything other than making the kwarg more visible in the examples.

[glwagner]

Maybe we shouldn't include in the examples though right? What's the point?

[navidcy]

It was hidden. Until it’s in a land model or somewhere else this is the way to include the river runoff and it was quite hidden.

I didn’t add anything. I just made the kwarg explicitly use false instead of relying to defaults.