http://www.bbm.me.uk/FeFert/U316/Introduction.htm
Introduction
'Scientists' and the much of world are waking up to global warming. The main
cause is industrial emissions of greenhouse gases, with carbon dioxide the
principle culprit.
Since the discovery that some marine areas are barren due to an iron
deficiency, one suggestion for amelioration of global warming is to enrich
those seas with iron. The proposal relies on:
iron-fertilisation of the oceans, to
increase phytoplanktonic activity, to
increase carbon dioxide draw-down from the atmosphere, to promote (possible)
long-term storage of carbon on the ocean-floor
The Science
The Biological Pump
While oceanic phytoplankton constitute <1% of the global photosynthetic
biomass, it accounts for almost half of all photosynthesis on Earth - a process
which removes carbon from the atmosphere. In the seas, phytoplankton use carbon
dioxide dissolved in sunlit surface waters, while a gas-equilibrium is
maintained across the ocean-air interface.
Most of the phytoplankton-biomass is eaten and enters the ocean food web. Some
decomposes, and some forms aggregates with waste products and sinks to the
ocean floor as 'marine snow'. There, a small proportion gets buried, while the
rest decomposes or remains suspended in water. Ultimately, all the constituent
organic carbon (except that buried) returns to the surface, through upwelling
or the marine food chain.
High nutrient low chlorophyll (HNLC) areas
Many seas are unproductive, even those with high levels of the common limiting
nutrients nitrogen, phosphorus and silicate. Already in the 1930's, it was
suggested that this low productivity was due to an iron-deficit.[1]
This was particularly noticed around the Galapagos Islands, where the areas
down-wind (or down-current) of land supported life, whereas those up-wind were
clear blue, and 'dead'. The aim of iron-fertilisation is to mimic the
productive, nutrient-rich coastal zones in the open ocean.
Both geological records and recent experimentation support this theory.
Palaeo-environmental Records
Analysis of ocean sediment cores from the past 180,000 years suggest that ice
ages were preceded by unusually-high levels of iron, usually attributed to
wind-blown dust from dry continents. This terrigenous iron rectified the
natural oceanic iron-deficit, causing phytoplankton blooms. These used carbon
dioxide from the surface waters, so equilibration of the ocean-atmosphere
interface reduced atmospheric carbon dioxide. This led to global cooling and
ice ages.
The Motivation
As iron is cheap and plentiful, the addition of controlled amounts to the
oceans to promote global cooling is an attractive proposition.
Carbon Trading
However; the most enthusiastic protagonists are not those concerned with
climate change per se, but with profit. The Kyoto Protocol's carbon-trading
allows owners of carbon sinks to sell their 'carbon credits' to the polluters.
These are the fossil-fuel-burning industries and nations, who are facing
emission-restriction legislation.
Carbon-trading applies only to terrestrial sinks (e.g. reforestation); but
ocean venturers want it extended to the marine arena. Then, plankton blooms
resulting from artificial iron fertilisation might earn carbon-credits, a
valuable commodity in the global market.
Estimates suggest iron-fertilisation might cost as little as US$1-2 per tonne
of carbon fixed, against US$50-200 for other proposed sinks[2,3]. This relative
low cost offers a high profit motivation in a global market. Industrial nations
could then buy 'rights to pollute' cheaply, while continuing to burn fossil
fuels within emissions-treaty agreements. Commercial and political interest is
thus high.
Issues
Is the proposal appealing - or appalling?
Of greatest concern are the marine ecology and ocean dynamics. Intentionally
geo-engineering the ocean presents problems both known and unknown.
While ecological changes have been detected in the experiment sites, no proof
of long-term carbon-sequestration has been found.
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References:
[1] Harvey, 1938. Often cited, e.g. in "The iron hypothesis: Basic research
meets environmental policy" in 'Reviews of Geophysics' vol. 33. 1995. Sallie W.
Chisolm http://www.sasayama.or.jp/diary/iron.htm
[2] Climate Engineering: A critical review of proposals, their scientific and
political context, and possible impacts (section 2.3.5). November 1996. Ben
Matthews http://www.chooseclimate.org/cleng/part1b.html
[3] "Climate change: Will Ocean Fertilization Work?" Science. April 4th 2003.
Buesseler, citing Markels at the 220th ACS Annual Meeting, Symposium on CO2
Capture, Washington, DC, 20-24 August 2000
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Home Home.htm
** Current Page ** Introduction.htm
Principle Protagonists, Alternative Views: Alternative.htm
Evidence of Natural Fertilisation: Evidence.htm
Experimental results: Experiments.htm
Is it Legal, Is it Safe, Will it Work? FAQ.htm
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Summary.htm |
Date last published: 07-Oct-03
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