[MITgcm-support] Blocking of light by sea ice and plankton

[Matthew Mazloff]

Hi Andrew

1) 2 cases:
i)  If you are using the external forcing package (EXF) and the sea ice package it uses the short wave flux calculated by these packages as long as you have 
#define USE_EXFQSW in BLING_OPTIONS.h
This does take into account sea ice cover

ii) If you are not using EXF (or BLING_OPTIONS has #undef USE_EXFQSW) then it simply takes light based on calendar day and neglects the influence of sea ice. You could make it account for ice in this case by uncommenting 
cav         irr_surf(i,j) = irr_surf(i,j)*(1. _d 0 - FIce(i,j,bi,bj))
in bling_light.F to make it dark under ice…or do something more sophisticated if you want. (Here FIce is the ratio of ice cover in the cell.)

2) BLING does not take self-shading by biomass into account. 

Hope this helps!
-Matt


> On Mar 27, 2018, at 4:16 AM, Andrew Twelves <agt_94 at hotmail.co.uk> wrote:
> 
> Morning all,
>  
> I am about to start biogeochemical modelling using the BLING package, and have a couple of questions regarding the treatment of light availability:
>  
> Does BLING by default set light penetration to zero underneath sea ice, or does it allow for limited penetration subject to a strong attenuation coefficient?  If the latter, does BLING take the value of effective sea ice thickness HEFF directly from the Sea Ice package, or does it do something more sophisticated (like a sub-grid scale parametrization of the thickness distribution)?
> Does BLING take the self-shading effect of phytoplankton themselves into account for light calculations?
>  
> I appreciate that these are potentially broad questions but any guidance would be much appreciated.
>  
> Many thanks in advance,
>  
> Andrew Twelves
> University of Edinburgh
> 
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