Ocean acidification below the surface

The climate change deniers say that climate change and relevant concerns are a fad. Well they must be wrong. From my personal experience I was reminded of [the climate change scenario](http://www.jstor.org/action/doAdvancedSearch?q0=global+warming&f0=all&c0=AND&q1=&f1=all&c1=AND&q2=&f2=all&c2=AND&q3=&f3=all&wc=on&sd=1980&ed=1989&la=&jo=&Search=Search) in 1980s -- right, before I went out of the kindergarten -- and that was like 20 years ago. And scientists today are using data that are accumulated continuously in the past 20 years to study the impact of climate change.

One instance is this [preprint](http://www.pnas.org/content/early/2009/07/24/0906044106.abstract) published on the PNAS website. The authors creatively used the fixed-temperature pH data, avoiding problems like the change of H₂CO₃ equilibria with temperature, and making the seasonal trend pronounced. It is pointed out that there is a trend of decreasing pH at sea surface, and more importantly, the seasonal pattern of water change between surface and sub-surface zones of the ocean may be a profound factor in a more complicated ocean acidification picture.

There are drivers at different scales at play here, causing diurnal, seasonal and annual variabilities of the ocean acidity. The authors mentioned a strong pH negative anomaly in 1998, which causes me to think whether there could be some cross-scale interactions, such as El Nino, also at play.

Another thought that occurred to me is that the dissolved organic carbon may be a slow variable in the ocean system. Of course I am not an oceanographer and this is just a wild guess. But if there is any oceanographer reading, would you care to explain the circulation of inorganic carbon in the ocean? We all know the acidity in the ocean is slowly increasing, but if there is an accumulation process of inorganic carbon that we do not know, one day it is going to give us a bigger surprise given adequate temperature and mixing conditions.

John E. Dore, Roger Lukas, Daniel W. Sadler, Matthew J. Church, & David M. Karl (2009). Physical and biogeochemical modulation of ocean acidification in the central North Pacific Proceedings of the National Academy of Sciences of the United States of America DOI: 10.1073/pnas.0906044106

Iron the sea to combat climate change

[http://www.sciencemag.org/cgi/content/full/318/5855/1368](http://www.sciencemag.org/cgi/content/full/318/5855/1368)


With no doubt, climate change is one of the biggest challenge the mankind faces in the new century. Perhaps this explains why there are quite some strange proposal to battle increasing green house gases. For example, there are some researchers proposed to [increase aerosol in the atmosphere to block solar radiation](http://www.guardian.co.uk/environment/2007/jan/27/usnews.frontpagenews) as aerosol is observed to lead to [temperature decrease in some cities in China](http://www.terradaily.com/reports/Haze_Dynasty.html) and [may cancel out some effects of global warming](http://www.sciencemag.org/cgi/content/summary/283/5406/1273). This somehow reminds me of ``Operation Dark Storm'' in [Animatrix](http://en.wikipedia.org/wiki/The_Second_Renaissance#Part_II). But of course such a proposal will get almost nil support from any reasonable person.

Now here is the new idea: pump iron into the sea. As the sea has a sufficient level of nutrient already and iron is the limiting factor, this will lead to virtually an explosion of algae which will need considerable amount of carbon to grow and will rapidly sink into the sea, which may be a way of sequestrating carbon. If practical, this will be a cheap solution to reduce carbon in the atmosphere. However, from the article in science you can read a lot of suspicions with various reasons: altered ecosystem, the efficiency of the sinking process, and the methane and nitrous oxide emitted in the process.

As there are too many uncertainties, further experiments are desirable. This is supported by some companies which hope to earn some credits in the carbon trading system. Personally I hope the experiment a success. However I also have my own doubt: will the sea saturate? There are reports saying that the capability of ocean carbon sinks are decreasing, and in a recent article, Canadell et al. states:

[C]arbon emissions have grown faster than CO2 sinks on
the land and oceans. Because the land and oceans are
both mosaics of regions that are gaining and regions that
are losing carbon, this trend could result from any or all
of three scenarios: sink regions could have weakened,
either absolutely or relative to growing emissions; source
regions could have intensified; or sink regions could have
transitioned to sources. (Canadell et al. 2007)

And Le Quere et al. (2007) have reported that the Southern Ocean is losing ability to absorb carbon dioxide and becoming a source instead.

I know very little about the metabolism of algae and the biochemical process in the ocean, but I think the researchers proposing the experiment should also consider carbon that cannot make it to a depth below 500 metres. Will they enter the ocean and accelerate the saturation of carbon? If so, in what condition?

My other complain is that this proposal, even if a success, should not be relied upon as a solution to climate problem. It should function more as a means to slow the process of climate change and earn some time for mankind to ultimately solve the carbon balance. I am worried that successful carbon sequestration will only lead to more emission. A mature carbon trading system may help, but a global monitoring and enforcement system urging everyone's adaptation to cleaner energy and smaller carbon footprint is the solution.

1. J. G. Canadell et al., [“Contributions to accelerating atmospheric CO2 growth from economic activity, carbon intensity, and efficiency of natural sinks,”](http://www.pnas.org/cgi/reprint/0702737104v1.pdf) Proceedings of the National Academy of Sciences (2007).

2. C. Le Quere et al., “Saturation of the Southern Ocean CO2 Sink Due to Recent Climate Change,” Science 316, no. 5832 (June 22, 2007), [http://www.sciencemag.org/cgi/content/abstract/316/5832/1735](http://www.sciencemag.org/cgi/content/abstract/316/5832/1735).