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Ozone depletion causing less oceanic CO2 uptake

post #1 of 5
Thread Starter 
This isn't very exciting, but it's kind of almost interesting so I thought I'd share. Basically stratospheric ozone depletion is increasing the strength of certain winds near the surface, which drive up carbon rich water from below the surface. This increases the amount of carbon near the surface, and so decreases the amount that can be absorbed from the atmosphere.

http://www.agu.org/pubs/crossref/2009/2009GL038227.shtml

Quote:
Abstract: 

Observational and atmospheric inversion studies find that the strength of the Southern Ocean carbon dioxide (CO2) sink is not increasing, despite rising atmospheric CO2. However, this is yet to be captured by contemporary coupled-climate-carbon-models used to predict future climate. We show that by accounting for stratospheric ozone depletion in a coupled-climate-carbon-model, the ventilation of carbon rich deep water is enhanced through stronger winds, increasing surface water CO2 at a rate in good agreement with observed trends. We find that Southern Ocean uptake is reduced by 2.47 PgC (1987–2004) and is consistent with atmospheric inversion studies. The enhanced ventilation also accelerates ocean acidification, despite lesser Southern Ocean CO2 uptake. Our results link two important anthropogenic changes: stratospheric ozone depletion and greenhouse gas increases; and suggest that studies of future climate that neglect stratospheric ozone depletion likely overestimate regional and global oceanic CO2 uptake and underestimate the impact of ocean acidification.


They even quantified it on a global level, saying that ozone depletion since 1975 caused atmospheric CO2 concentrations to be 1.2 ppm higher by 2004 than they would be without this effect.

They also claim that this upwelling of deep water is accelerating ocean acidification (yes, in spite of the lower absorption of anthropogenic carbon). That part doesn't make a whole heck of a lot of sense to me, and they don't really explain it in the article.
post #2 of 5
Quote:
Originally Posted by dawei View Post

This isn't very exciting, but it's kind of almost interesting so I thought I'd share. Basically stratospheric ozone depletion is increasing the strength of certain winds near the surface, which drive up carbon rich water from below the surface. This increases the amount of carbon near the surface, and so decreases the amount that can be absorbed from the atmosphere.

http://www.agu.org/pubs/crossref/2009/2009GL038227.shtml



They even quantified it on a global level, saying that ozone depletion since 1975 caused atmospheric CO2 concentrations to be 1.2 ppm higher by 2004 than they would be without this effect.

They also claim that this upwelling of deep water is accelerating ocean acidification (yes, in spite of the lower absorption of anthropogenic carbon). That part doesn't make a whole heck of a lot of sense to me, and they don't really explain it in the article.

Deep water is high in dissolved CO2, therefore more acidic.  When it comes to the surface, it leads to higher total acidity in the surface water, at least until the excess CO2 outgasses to the atmosphere. 
post #3 of 5
Thread Starter 
Quote:
Originally Posted by gcnp58 View Post

Deep water is high in dissolved CO2, therefore more acidic.  When it comes to the surface, it leads to higher total acidity in the surface water, at least until the excess CO2 outgasses to the atmosphere. 

But...all that does is shift the carbon from the deep ocean to the surface, it won't change the net carbon content or pH of the ocean as a whole. And the fact that it's having the effect of reducing the amount of new carbonic acid that is being dissolved into the ocean would mean that it is slowing the rate of acidification--again, as a whole. Right?
post #4 of 5
Quote:
Originally Posted by dawei View Post

But...all that does is shift the carbon from the deep ocean to the surface, it won't change the net carbon content or pH of the ocean as a whole. And the fact that it's having the effect of reducing the amount of new carbonic acid that is being dissolved into the ocean would mean that it is slowing the rate of acidification--again, as a whole. Right?

Yes, kind of, but the net effect is for the ocean surface pH to go down.  The carbon in the deep ocean is present as carbonic acid, so the pH of deep water is lower than surface water.  When it comes to the surface, the mixing with the surface water lowers the pH of the surface water, in a sense acidifying the surface.  It's not acidifying the whole ocean, just the surface.  But since that's where the effects of acidification are most important, that's why it's considered acidifying the ocean.  You can see this in maps of ocean surface pH, where the lower pH water in the Eastern Pacific are due to the upwelling deep water off of Peru. 

If you compare that map to the map of projected ocean acidification you see the effect you are talking about, where the excess CO2 from the deepwater buffers the surface water to reduce the net decrease in pH due to anthropogenic CO2.  But the critical thing to look at is the first map, and see that when you bring deepwater to the surface in places where it wasn't upwelling before, there is a large acidification of the surface. 
post #5 of 5
Thread Starter 
Quote:
Originally Posted by gcnp58 View Post

It's not acidifying the whole ocean, just the surface.  But since that's where the effects of acidification are most important, that's why it's considered acidifying the ocean.  You can see this in maps of ocean surface pH, where the lower pH water in the Eastern Pacific are due to the upwelling deep water off of Peru. 

Gotcha. They really should have said "surface acidification" then. Where can I call to complain?
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