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*Subject*: Re: More on alkalinity*From*: jls@splash.Princeton.EDU (Jorge L. Sarmiento)*Date*: Thu, 13 Mar 1997 08:16:14 -0500 (EST)

Hi Jonathan, The decision to use global mean alkalinity for the solubility pump was made by Rick Murnane and I in the study first reported in our 1995 paper in the Proceedings of the Royal Society. We wanted the difference between the combined and solubility models to represent the FULL effect of biological processes, including the reduction of surface alkalinity due to CaCO3 formation. Thus we fixed the mean solubility pump alkalinity to the mean observed alkalinity, NOT correcting for the surface reduction due to biological removal to the deep ocean. Obviously, it does not make sense to use the solubility model defined this way to estimate anthropogenic CO2 uptake, although, as Rick pointed out, the effect is not very large. The choice of how to proceed from this point onwards should depend on what one is trying to achieve. If you want to use the solubility model to estimate the anthropogenic CO2 uptake, then you should indeed use the mean surface alkalinity, not the mean global alkalinity. However, I would be opposed to using the solubility model to estimate oceanic uptake. That should be done with the combined model. In that case, the value of the solubility model is as a contrast to the combined model to illustrate what biology does. We may decide that the way Rick and I defined the solubility model is not ideal for this latter purpose, but I would suggest that if we want to change the definition of the solubility model, we should do it with the idea that we want to use it as a contrast to the combined model in order to identify the contribution of the biological pump. Best regards, Jorge >Hello OCMIP people, > >Thanks to everyone who replied to my alkalinity query. >It would seem that 2311*S/34.78 ueq/kg is a more reasonable expression >to use for surface alk than 2374*S/34.78. > >As high latitude alkalinities are significantly higher than lower latitudes >does this imply a strong alkalinity component to the solubility pump? > >From some very simple calculations using: > >High latitude T=5C S=35o/oo ALK=2370ueq/kg >Low latitude T=25 S=35o/oo ALK=2285ueq/kg > >I find that the potential surface TCO2 high-low lat difference is enhanced >by 40% over the case where both high and low lat alkalinities are 2310ueq/kg. >Hence getting the surface alkalinity distribution right could significantly >affect solubility pump calculations. > >Any comments? > >JonathanP. > > >????????????????????????????????????????????????????????????????????? > JONATHAN PALMER >Room H013, Internet: JRPalmer@meto.gov.uk >Hadley Centre, >Met. Office, London Road, Tel: +44 (0)1344 854478 >Bracknell, RG12 2SZ, UK Fax: +44 (0)1344 854898 >????????????????????????????????????????????????????????????????????? Jorge L. Sarmiento AOS Program, Princeton U. Sayre Hall P.O. Box CN710 Princeton, NJ 08544-0710 Tel. (609) 258-6585 Fax. (609) 258-2850 E-mail: jls@splash.princeton.edu

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