Iron's the answer!

So we have now set the processes of Geoengineering in motion....

But what actually is Geoengineering?

I reiterate my previously brief introduction on what composes the term 'Geoengineering' by first defining the process as 'as an intentional large scale manipulation of the environment...' (Keith, 2000).  The action of geoengineering must be primarily for inducing environmental change, and on a large scale (continental or global). The currently credible methods of Geoengineering can be divided into Carbon Dioxide Removal (CDR) and Solar Radiation Methods (SRM).

This post will focus on all processes CDR related. So what are they?

They have one aim. 

Carbon dioxide removal methods resolve to reduce the amount of carbon dioxide within the atmosphere through extraction for long term storage in a sink such as land, vegetation or sequestration in the deep ocean (Hamilton, 2013). This process manipulates the mighty global carbon cycle, shifting the current equilibrium balance away from its present state of an increasingly enlarging atmospheric carbon sink. The removal of atmospheric carbon dioxide should slow then begin to diminish the increasing warming effects that excess carbon dioxide has already caused. 

Ocean Iron Fertilisation is one of the CDR approaches and will be the focus of today's post.

The world's oceans are crucial within the global carbon cycle, as the largest sink of carbon. More than 38,000 billion tonnes of carbon are stored in the ocean,compared to 800 billion tonnes in the atmosphere (Hamilton, 2013). Carbon dioxide initially dissolves into the ocean surface layer where great mixing occurs. This surface layer becomes saturated quickly, and carbon is then drawn down into the deep ocean. Little mixing occurs in the deep ocean so carbon storage is greater. Ocean temperature is an important variable in the uptake of carbon, as colder waters are able to absorb greater quantities of carbon, therefore deep oceans at high latitudes are optimum for carbon storage.

Ocean iron fertilisation has been proposed to increase biological productivity through increased iron content within the waters. The increased productivity would induce an increase in carbon uptake within the deep oceans through photosynthesis. Iron is an important trace element for all living organisms, but increasingly so for cellular functions including chlorophyll synthesis in phytoplankton to undertake photosynthesis processes.

Phytoplankton growth is more prolific in areas of high nutrients and low chlorophyll, such as the Southern Ocean and sub-Arctic Pacific (Allsop et al. 2007) due to the lack of availability of iron. Phytoplankton blooms are stimulated by increased iron content, and iron fertilisation is idealised as a geoengineering preposition to enhance the biological pump through phytoplankton population growth, to draw more carbon dioxide into the oceans. When these micro-organisms perish, the carbon is stored for a very prolonged period within the deep ocean. (The video below describes the iron fertilisation process with the bonus of visual aids). One tonne (metric ton) of iron could promote the removal of 30,000 to 110,000 tonnes of carbon from the atmosphere, and the process of iron fertilisation is estimated to cost only approximately $30-300 per tonne of carbon sequestered (White & Mitchell, 2012). 

Sounds great, right?

Surely this process could mitigate climate change? 

(Source: www.youtube.com/watch?v=sPRKLpDdM0s) 

As easy as this all sounds there are limitations.

Firstly there is a huge lack of understanding within this area of research, and the concepts are highly simplified (Allsop et al. 2007).  There have been only 12 small scale experiments between 1993 and 2008 to see the impact that increased iron concentration has on phytoplankton growth, with successful results (Lampitt et al. 2008), but none of these experiments were designed to measure sequestration. Since then, there have been 2 more, including a  release of 100 tonnes of iron sulfate into the North Pacific Ocean, just off Canada in 2012 (Tollefson, 2012), but this sparked conflict and experimentation ceased (Bellamy, 2014). No project has yet been applied on a large scale, which could have great hindering effects or hitherto unforeseen consequences. Therefore whilst the potential is there to enhance ocean carbon sequestration by this technique, modelling and observation attempts have not yet provided a foundation stable enough for this method to develop further (Lampitt et al. 2008) due to lack of verification. All methods have to be verified in front of policy-makers and the scientific community for success, (this can be illustrated by the advent of carbon credits within policy) yet such certainty of outcomes is not yet demonstrable for iron fertilisation. 

Source: Translating Science

Similarly a large envelope of uncertainty surrounds the methodology due to unknown global carbon cycle processes and interactions with the upper ocean. Side effects of iron fertilisation could be ocean acidification, due to increased carbon dioxide absorption into ocean surface layers. Such a decrease in ocean pH is likely to have implications and alternative effects on the ability for calcification and a shift in phytoplankton populations (Lampitt et al. 2008). 

The process could similarly cause a redistribution of minerals within the ocean, causing nutrient deficits elsewhere. Similarly increased phytoplankton populations could absorb more heat from the sun, and produce warmer ocean surface layers (Powell, 2008). 

There are big ethical problems - such as who owns the oceans? Whose piece of ocean shall we try this out on first? What about impacts on fish stocks and harvest from the sea? There are many interdependent and delicate ecological systems in the oceans? How do we assess the environmental impact of such complexity? Are adverse impacts on some species OK but not others? Who will decide?

The examples above are uncertainties to name a few. But the list goes on. There are too many uncertainties associated with ocean iron fertilisation, which are preventing it from becoming, in the near future, any more than a geoengineering application or proposal. 


However, which other carbon dioxide removal methods have been proposed - and with what likelihoods of future success?

Let's check these out next time!   


S xx