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. -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- Summary.htm | Date last published: 07-Oct-03
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