Ocean acidification and atmospheric carbon

  • #1
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Hi everyone

The following graph shows levels of CO2 in the oceans increasing with atmospheric CO2.

https://ocean.si.edu/conservation/acidification/ocean-acidification-graph

Given that global temperatures should rise with CO2, is it theoretically possible for the oceans warm to the point where their ability to hold CO2 decreases? That is, there is a point after which the ocean will become less acidic as atmospheric CO2 increases (not that this will help anything).


Thanks
 

Answers and Replies

  • #2
256bits
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Hi everyone

The following graph shows levels of CO2 in the oceans increasing with atmospheric CO2.

https://ocean.si.edu/conservation/acidification/ocean-acidification-graph

Given that global temperatures should rise with CO2, is it theoretically possible for the oceans warm to the point where their ability to hold CO2 decreases? That is, there is a point after which the ocean will become less acidic as atmospheric CO2 increases (not that this will help anything).


Thanks
Hi Darlmisc.
Is that a graph representing surface sea water only, or representative of whole ocean concentration?
How much time does it take for the ocean's waters to mix? days, years, centuries?
 
  • #3
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I'm afraid I don't know any more than what's in the description under the graph.

I hadn't even thought about whether the deep ocean is affected by acidification (and warming). Would the question make sense if it were just confined to the surface water? I'm picturing a scenario similar to how soft drinks go flat at room temperature. Would this happen to the ocean? Or would high concentrations of atmospheric CO2 mean that overall, the pH continues to drop?
 
  • #4
256bits
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I'm afraid I don't know any more than what's in the description under the graph.

I hadn't even thought about whether the deep ocean is affected by acidification (and warming). Would the question make sense if it were just confined to the surface water? I'm picturing a scenario similar to how soft drinks go flat at room temperature. Would this happen to the ocean? Or would high concentrations of atmospheric CO2 mean that overall, the pH continues to drop?
Also good questions.
I just noticed that the graph is data from off the coast of Hawaii.
Surface water changes in CO2 content and acidification, and as you mentioned temperature change, would affect the flora and fauna living in the shallow depths - what's a shallow depth - I couldn't find the extent to which they measured.
Ocean mixing has to happen as I would think that the oxygen down deep below has to be from the atmosphere/sea interface and brought down, as would also CO2. I do wonder as to the amount of stratification per depth of the items mentioned.
there has to be some sort of timetable for ocean mixing whether brought about more locally by storms such as hurricanes or typhoons, or more generally by the currents generated by the interaction colder pole seawater with warmer equatorial.
It seems to be an interesting subject to be in.
 
  • #5
256bits
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In regards to mixing, there is this,
https://www.theguardian.com/science...cient-greek-discovered-at-bottom-of-black-sea
or, a PF post,
https://www.physicsforums.com/threads/oldest-ship-wreck-found-in-black-sea.958439/#post-6077735

The guardian states,
... shipwreck at the bottom of the Black Sea where it appears to have lain undisturbed for more than 2,400 years.

The 23-metre (75ft) vessel, thought to be ancient Greek, was discovered with its mast, rudders and rowing benches all present and correct just over a mile below the surface. A lack of oxygen at that depth preserved it, the researchers said.
...
Although the Black Sea is not the oceans, is the mixing with depth of the oceans and Black Sea comparable in nature?
Would CO2 follow the same stratification?
Some questions for the peoples at the Smithsonian might want to follow up on at their site to give a clearer picture of what is going on in addition to their explanation of the interaction of the atmosphere and the water interface, and expand that as to how does the whole ocean can/will act as a CO2 sink - ie or is it surface water only..
 
  • #6
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Cheers. Thanks
 
  • #7
Bandersnatch
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There's a Wiki article on 'solubility pump' that might be worth looking into. Specifically, the references for the section on anthropogenic changes.
 
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  • #8
BillTre
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Although the Black Sea is not the oceans, is the mixing with depth of the oceans and Black Sea comparable in nature?
Would CO2 follow the same stratification?
The Black Sea is unusual in its lack of mixing between top and bottom layers.
Some attribute this to a heavier saltier layer under the fresher water which is continuously entering the sea from rivers.
 
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  • #10
olivermsun
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It seems quite likely that pCO2 is measured from surface water.

Ocean mixing has several timescales — the mixed layer at the surface might be well mixed over less than a day; the upper ocean below the mixed layer might be mixed on timescales of months to a few years. The very deep ocean, which is basically never exposed to direct wind forcing (except at key locations), probably would not equilibrate for a millennium or more.
 
  • #11
Baluncore
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Given that global temperatures should rise with CO2, is it theoretically possible for the oceans warm to the point where their ability to hold CO2 decreases?
CO2 in the ocean is in equilibrium with CO2 in the atmosphere, but with a long time constant. The temperature of the ocean would have to rise very significantly before CO2 stopped moving from the atmosphere into the ocean. We can expect pH to continue to fall if atmospheric CO2 continues to rise at the present rate.

There is a worrying pH interaction related to the iron cycle in the ocean. Phytoplankton require two doses of iron one week apart to mature. They then convert CO2 into O2 and organic carbon compounds. Later, they are eaten by krill that are in turn eaten by whales, that excrete the two doses of iron needed for the next generation of phytoplankton. If we break that iron cycle we greatly reduce the phytoplankton population replacement and the CO2 to O2 transformation.

There is some good news and some bad news. First the good news is you don't need to worry about the solubility of CO2 in warmer seawater. But the bad news is that the pH limit on krill exoskeleton formation is rapidly approaching and will reach us long before temperature limits the solubility of CO2 in seawater. It seems we are going to have to trust in the rapid evolution of krill stocks that can build an exoskeleton in progressively more acidic seawater.

This is a good argument for increasing the whale population, and for avoiding the harvest of krill, which is a significantly lower cost option than manufacturing and dumping bio-available iron in the Ocean.
 
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