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Re: CaCO3 dissolution



Ray Najjar wrote:
> 
> OCMIP, I am forwarding Ken's reply, with a reply by me below.  -Ray Najjar
> 
> >From kenc@llnl.gov Fri Jun 26 11:44 EDT 1998
> X-Sender: e129798@poptop.llnl.gov
> Mime-Version: 1.0
> Date: Fri, 26 Jun 1998 08:47:21 -0700
> To: Ray Najjar <najjar@essc.psu.edu>
> From: Ken Caldeira <kenc@llnl.gov>
> Subject: 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
> >saturation
> >horizons are at very different depths.
> >
> >Ray
> 
> 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.
> 
> Cheers,
> 
> Ken
> 
> <--------------------------->
> 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
> 
> ----- End Included Message -----
> 
> 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


Ken and Ray:

Thanks for including the chemists in on your discussions.  I suggest
that you look
at a suite of papers by Bob Byrne and his colleagues (Byrne et al.,
Nature 312 (5992): 
321-326 (1984), Acker et al., GCA 51: 2171-2175 (1987), Feely et al.
Marine Chem. 25: 
227-241 (1988).  These papers give equations for carbonate dissolution
as a function
of the degree of saturation.  This term can be determined from DIC and
alkalinity data.
The equations have been verified with insitu dissolution studies. 
Different coefficients 
 are required for calcite and aragonite but the equations are of the
same form.  I hope
this information is helpful. For more details i would contact Bob Byrne.

Regards, Dick.
- -- 
Richard A. Feely
Pacific Marine Environmental Laboratory
National Oceanic and Atmospheric Administration
7600 Sand Point Way NE
Seattle, WA 98115
(206) 526-6214 Phone
(206) 526-6744 FAX
e-mail:  feely@pmel.noaa.gov
http://www.pmel.noaa.gov/co2/co2-home.html