[MITgcm-support] Re: question about seaice coupling to ocean velocities

[Dimitris Menemenlis]

Hi Jinlun, Martin just sent in following question.  Can we change
reference velocity to some fixed depth, could also be a variable
depth, right below KPPhbl.  What do you think?

> Hi,
> I may have asked this before, but couldn't find the answers (if there 
> where any) in the email archives:
> What's the reason for using the third level (k=3) velocities 
> u/vVel(i,j,3,bi,bj) as "proxy for geostrophic velocities" in 
> seaice_model.F? It is reasonalbe to assume that only the 3rd level 
> velocities excert stress on the sea ice from below? If you are willing 
> to accept that the surface velocities are too noisy to be used, 
> shouldn't the k-level be connected to a certain depth and not to a hard 
> coded k-level? I mean, in a coarse model with, say, 50-70m layer 
> thickeness (as in global_ocean_90x40x15 and derivatives) this will have 
> a completely different effect from a model with resolves the surface 
> layers rather well (say 10m in the upper 100m). What's the rationale 
> behind the choice of k=3?
> 
> Martin

Martin, my take on this is that it is just a quick-and-dirty estimate of
surface geostrophic velocity and that it would make more sense to
connect the k-level to a certain depth and not to a hard-code the
k-level.  What's needed is velocity right below or near the bottom of
the Ekman layer.

D.

-- 
Dimitris Menemenlis <menemenlis at jpl.nasa.gov>
Jet Propulsion Lab, California Insitute of Technology
MS 300-323, 4800 Oak Grove Dr, Pasadena CA 91109-8099
tel: 818-354-1656;  fax: 818-393-6720