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On CO2 and the ocean--how can I calculate it?

post #1 of 4
Thread Starter 

I want to calculate the net ocean-atmosphere flux of CO2 . I know there are a lot of sources that the net flux is into the ocean, but I would like to see the actual equations, which should be pretty simple right?

 

I mean we know the partial pressure change in the air, we know the total concentration of carbonate in the water, we know the temperature rises of the ocean, we know the constant of gas/air exchange for the ocean...I know there are a few other complications but that should be more or less the end of it.

 

I'd try to do it myself, but someone must have done this on a more advanced level a long time ago. Anyone know off hand where I could find it?

post #2 of 4

I have not done the calculation, but I think that the model should divide the ocean into regions and then take a weighted average.  The temperature and composition of ocean water varies and this should have an effect.

post #3 of 4
Thread Starter 

 

Quote:
Originally Posted by Whiteshell001 View Post

 

I have not done the calculation, but I think that the model should divide the ocean into regions and then take a weighted average.  The temperature and composition of ocean water varies and this should have an effect.

 

Yeah that's a good point. I'm also wondering if it might be more complicated than I thought. I mean the change in carbonate concentration wouldn't just be affected by CO2 getting disolved into it, but also CaCO3 getting protonated by the carbonic acid. This could make some molecules of CO2 raise the TOTco3 count by twice than they would just by absorption alone. Blah.

post #4 of 4

Ocean acidification is generally thought of in terms of a chemical equilibrium process so you don't take the gas exchange rate into account.  In physical terms, this is equivalent to saying the ocean surface mixed layer equilibrates instantaneously with the increasing CO2 in the atmosphere.  This is more or less true, the true equilibration time is on order of a year globally, but CO2 doesn't change all that much over a year. 

 

So, what you need to do to calculate the effect of increasing atm. CO2 on ocean pH is get the manual for CO2 calculations in seawater published by CDIAC as part of the old DOE-Oceans CO2 program (google "Dickson Goyet Scripps CO2 manual" or similar terms and you should find it).  Then you need to find maps of ocean surface total alkalinity and one of the parameters of the carbon system, either DIC or pCO2.  Using the equations in the CO2 manual linked above, you can work out the CO2 chemistry regionally in the ocean, and from that figure out how the surface pH changes due to a doubling of atmospheric CO2. 

 

Setting up the equations is relatively straightforward if you are used to dealing with acid-base chemical calculations.  If you're not it can be a little confusing.  There are canned programs for doing this (e.g., here, the Lewis and Wallace reference) and you could use one of them instead. 

 

 

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