[ecco-support] surface pressure in LLC4320

[Matthew Mazloff]

Hello 

We love the LLC4320 - thank you!

We are analyzing the SO dynamics in it, and we need to know surface pressure. However ETAN appears to be the water column height under the sea ice. Is this correct - do we need to add sea ice loading?

If so would it be 
            sIceLoad  = HEFF * SEAICE_rhoIce + HSNOW * SEAICE_rhoSnow
And then 
	phiSurf = ( etan + sIceLoad*recip_rhoConst ) *gravity

Much appreciated!
Matt