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CaCO3 dissolution

>The other issue is CaCO3 dissolution in the water
>column.  The state of the art now is to have a constant e-folding depth for
>dissolution, but clearly it is not this simple--there must be differences,
>for example, between the North Atlantic and North Pacific, where the
>horizons are at very different depths.

I am running now with CaCO3 dissolution depending on the local CO3=
concentration [a very simple parameterization].   Doing this gives a nice
additional set of observables to compare against.

You can specify riverine CaCO3 inputs, and the CCD will adjust such that
sedimentation balances inputs.  However, if you do this total alkalinity
and tCO2 will drift. Alternatively, you can specify that riverine CaCO3
inputs balance sedimentation, thus keeping ocean alkalinity constant.

If the goal is to show off model inadequacies this is a good thing to do.
My model generates too much corrosive Antarctic Bottom Water, and whereever
it goes there is no carbonate accumulation, and it goes where it should not.

The hang up is having to compute deep ocean chemistry; however, you don't
need to recalculate it every time-step as the chemistry is slowly changing.



Ken Caldeira
Climate System Modeling Group
Lawrence Livermore National Laboratory
7000 East Ave., L-103
Livermore CA 94550 USA

tel: (925)  423-4191 (new area code!)
fax: (925)  422-6388
e-mail:  kenc@LLNL.gov

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Ken, it makes sense to make dissolution a function of CO3-, but how do you
decide the functionality, by tuning to the observed Alk distribution or from
experimental data?  With regard to external inputs/outputs I like adjusting
riverine input to be equal to model sedimentation rates; we might as well use
what we know better--the mean alkalinity of the ocean as compared to riverine
Ca inputs.  Of course, this means you need a sediment model like Archer/Maier-
Reimer have done.  -Ray