In a warming world, at what point do the oceans flip from a carbon sink to a carbon source?

[NickB79]

A friend and I were discussing global warming and the acidification of the world's oceans, and an interesting question came up. If the world's oceans were to reach a saturation point with regard to CO2, the amount of CO2 left in the atmosphere would increase even more per year than it is now. Essentially, the buffering ability of seawater would be gone since no more CO2 could be absorbed. The extra CO2 not absorbed in turn would drive global temps up higher and faster, and the oceans would warm much more rapidly than expected. Warm water would hold less CO2 than cooler water, though.

At this point, would the world's oceans become carbon positive, releasing decades of stored CO2?

[begin_within]

1. When they become "Presented by Coca-Cola"

[Richard D]

2. At what point?

Not very far away, I'm afraid.

[OKIsItJustMe]

3. Well, for one thing, when you drop atmospheric CO2 levels, it'll start coming back out of the ocean

http://www.pnas.org/content/early/2009/01/28/0812721106.full.pdf+html

But, Methane may already be making them carbon sources:
http://blogs.discovermagazine.com/80beats/2008/09/24/methane-bubbles-in-the-arctic-ocean-give-climate-scientists-the-willies/

Methane Bubbles in the Arctic Ocean Give Climate Scientists the Willies

Alarming but preliminary reports of methane gas bubbling up from the Arctic Ocean have raised the specter of precipitous global warming in the minds of some climate scientists.

While aboard a research ship sailing off the coast of Siberia, scientists observed high levels of methane in the water, and then spotted several areas where the gas bubbles were fizzing up from the ocean floor, which contains vast amounts of frozen methane. That was enough to ring the alarm bells: Methane is about 20 times more powerful as a greenhouse gas than carbon dioxide and many scientists fear that its release could accelerate global warming in a giant positive feedback where more atmospheric methane causes higher temperatures, leading to further permafrost melting and the release of yet more methane .

While the news seems disquieting, some researchers are expressing some skepticism about the findings, which haven’t yet been published in a peer-reviewed journal. The initial word from a heap of scientists who are focused on sub-sea methane deposits, including a group that videotaped big burps of methane bubbles off Santa Barbara, Calif., a few years ago, is a note of caution about overinterpreting the Arctic bubbling and high gas concentrations as something a) new or b) driven by human-caused global warming .

Reporting from the boat, researcher Orjan Gustafsson said his team found some ocean areas where the methane levels were 100 times higher than average, and also observed areas of sea foaming with gas bubbling up through “methane chimneys” rising from the sea floor. They believe that the sub-sea layer of permafrost, which has acted like a “lid” to prevent the gas from escaping, has melted away to allow methane to rise from underground deposits formed before the last ice age .

…

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=115&topic_id=183130&mesg_id=183130

…

A moderate increase in sea-floor temperature could trigger the widespread release of methane from ocean hydrates, finds new research. Large quantities of the potent greenhouse gas are stored beneath the sea in solid crystalline structures, known as hydrates, that could potentially be destabilized by ocean warming.

…

[kestrel91316]

4. When they become Dead Zones and all organic matter in them

is undergoing anaerobic fermentation, producing vast amounts of methane. IOW, real soon now if we keep things up.

I have started to wonder if I might actually live to see the Big Dieoff.

[glinda]

5. I am afraid we might. Specially the way the Repubs are griping like there is no tomorrow.

[thereismore]

6. Yes, we're f*d. I hear time estimates like 50-100 years until hell breaks loose. nt