Personally I find the claims of 13000 tonnes to 1 atom of iron somewhat difficult to comprehend!
A
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Nature doi:10.1038/nature.2012.11028
Dumping iron at sea does sink carbon
Geoengineering hopes revived as study of iron-fertilized algal blooms shows they deposit carbon in the deep ocean when they die.
Quirin Schiermeier
18 July 2012
In the search for methods to limit global warming, it seems that stimulating the growth of algae in the oceans might be an efficient way of removing excess carbon dioxide from the atmosphere after all.
Despite other studies suggesting that this approach was ineffective, a recent analysis of an ocean-fertilization experiment eight years ago in the Southern Ocean indicates that encouraging algal blooms to grow can soak up carbon that is then deposited in the deep ocean as the algae die.
In February 2004, researchers involved in the European Iron Fertilization Experiment (EIFEX) fertilized 167 square kilometres of the Southern Ocean with several tonnes of iron sulphate. For 37 days, the team on board the German research vessel Polarstern monitored the bloom and demise of single-cell algae (phytoplankton) in the iron-limited but otherwise nutrient-rich ocean region.
Each atom of added iron pulled at least 13,000 atoms of carbon out of the atmosphere by encouraging algal growth which, through photosynthesis, captures carbon. In a paper in Nature today, the team reports that much of the captured carbon was transported to the deep ocean, where it will remain sequestered for centuries1 — a 'carbon sink'.
“At least half of the bloom was exported to depths greater than 1,000 metres,” says Victor Smetacek, a marine biologist at the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany, who led the study.
The team used a turbidity meter — a device that measures the degree to which water becomes less transparent owing to the presence of suspended particles — to establish the amount of biomass, such as dead algae, that rained down the water column towards the sea floor. Samples collected outside the experimental area showed substantially less carbon being deposited in the deep ocean.
Iron findings
The EIFEX results back up a hypothesis by the late oceanographer John Martin, who first reported in 1988 that iron deficiency limits phytoplankton growth in parts of the subarctic Pacific Ocean2. Martin later proposed that vast quantities of iron-rich dust from dry and sparsely vegetated continental regions may have led to enhanced ocean productivity in the past, thus contributing to the drawdown of atmospheric carbon dioxide during glacial climates3 — an idea given more weight by the EIFEX findings.
Some advocates of geoengineering think that this cooling mechanism might help to mitigate present-day climate change. However, the idea of deliberately stimulating plankton growth on a large scale is highly controversial. After noting that there were gaps in the scientific knowledge about this approach, the parties to the London Convention — the international treaty governing ocean dumping — agreed in 2007 that ‘commercial’ ocean fertilization is not justified (see 'Convention discourages ocean fertilization').
The finding that ocean fertilization does work, although promising, is not enough to soothe concerns over potentially harmful side effects on ocean chemistry and marine ecosystems, says Smetacek. Some scientists fear that massive ocean fertilization might produce toxic algal blooms or deplete oxygen levels in the middle of the water column. Given the controversy over another similar experiment (see 'Ocean fertilization experiment draws fire'), which critics said should not have been approved in the first place, the Alfred Wegener Institute will not conduct any further artificial ocean-fertilization studies, according to Smetacek.
“We just don’t know what might happen to species composition and so forth if you were to continuously add iron to the sea,” says Smetacek. “These issues can only be addressed by more experiments including longer-term studies of natural blooms that occur around some Antarctic islands.”
But some experts argue that artificial ocean-fertilization studies should not be abandoned altogether. “We are nowhere near the point of recommending ocean fertilization as a geoengineering tool,” says Ken Buesseler, a geochemist at the Woods Hole Oceanographic Institution in Massachusetts. “But just because we don't know all the answers, we shouldn't say no to further research.”
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Bhaskar
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Morton
Iron fertilization is planned to be used in HNLCs, i.e., areas that have high nutrient levels year after year.
So it appears that there is a abundance of nutrients in the oceans.
In the past the CO2 levels of atmosphere and oceans were lower due to natural factors and diatom growth higher, so nutrients to support this were available.
O2 levels of atmosphere is today ~ 21 %, peak was ~ 35%.
So nutrients to support more than 50% higher photosynthesis was available at that point in time.
P is available only as a solid or dissolved in water, never as gas.
N may exit lakes and oceans as N2 gas but not P.
So P to support much higher level of photosynthesis was and is available on land or in water, if it has to be transported it can be done - whether 100 tankers are required or 1000 tankers are required will be known only if we experiment.
Excess carbon in the atmosphere is about 200 billion tons - 390 ppm - 280 ppm.
At 100 : 1, total P requires is less than 1 billion tons.
Annual carbon emissions are 10 billion tons of C, P required is about 50 million tons.
Global Rock Phosphate production is 256 million tons.
Rock Phosphate reserves in Western Sahara alone are about 50 Billion tons.
http://minerals.usgs.gov/minerals/pubs/commodity/phosphate_rock/mcs-2012-phosp.pdf
There seems to be no danger of running out of phosphorus.
Before you ask how many tankers are required, please read -
African dust leads to large toxic algal bloom
http://eospso.gsfc.nasa.gov/ftp_docs/African_Dust.pdf
"Each year, several hundred million tons of African dust are transported westward over the Atlantic
to the Caribbean, Gulf of Mexico, Central America, and South America."
"Plant-like bacteria use the iron to set the stage for red tide, a toxic algal bloom. When iron levels
go up, these bacteria, called Trichodesmium, process the iron and release nitrogen in the water,
converting it to a form usable by other marine life. The increased nitrogen in the water makes the
Gulf of Mexico a friendlier environment for toxic algae. The image on the left shows a red tide
event that was seen by the SeaWiFS sensor on August 26, 2001. A huge bloom of toxic red algae,
called Karenia brevis (K. brevis), appears on the true-color image as a black area hugging the
Florida Gulf Coast from the Keys to Tampa Bay."
The dust contains P, Si and Fe.
N is fixed from atmosphere by cyanobacteria - Trichodesmium.
The key is to ensure bloom of useful algae and not harmful algae.
We have the key. We can prevent this dust from causing toxic algal bloom by a very scientific fertilization to cause a controlled bloom of diatoms instead of dinoflagellates (red tides).
regards
Bhaskar
On Saturday, 21 July 2012 17:31:15 UTC+5:30, O Morton wrote:
The level of atmospheric oxygen cannot rise indefinitely unless the frequency of forest fires becomes so excessive that plant life cannot persist. This has been pointed out by Watson et al. (27), who emphasize that fires serve as strong negative feedback against excessive O2 variation. Conversely, O2 cannot have dropped to such low values over Phanerozoic time that fires became impossible. Fossil charcoal, as evidence of paleofires, has been found for all times that trees have populated the land, and the lower limit for the production of charcoal has been estimated to be at about 13% O2 (28). By contrast, the upper limit for O2 is in dispute. On the basis of experiments on the ignition of paper strips at different oxygen levels and fuel moisture contents, Watson et al. (27) concluded that past levels of atmospheric O2 could never have risen above 25%. However, consideration of actual forest fires and the response of ecological disturbance to fires led Robinson (29) to conclude that greater O2 variation might occur and that, at any rate, paper is not a good surrogate for the biosphere. In fact, Robinson states paleobotanical evidence for a higher frequency of fire-resistant plants during the Permo-Carboniferous, supporting the idea of distinctly higher O2levels at that time."
Apparently there is evidence of more fires, and more fire resistant plants.--
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Mike
Historical oxygen levels are a question of fact.
No logic is involved.
Wikipedia
http://en.wikipedia.org/wiki/Atmosphere_of_Earth
A good graph of O2 levels
http://www.nap.edu/openbook/0309100615/gifmid/30.gif
http://www.pnas.org/content/96/20/10955.full
Oxygen and Paleofires.
The level of atmospheric oxygen cannot rise indefinitely unless the frequency of forest fires becomes so excessive that plant life cannot persist. This has been pointed out by Watson et al. (27 <http://www.pnas.org/content/96/20/10955.full#ref-27> ), who emphasize that fires serve as strong negative feedback against excessive O2 variation. Conversely, O2 cannot have dropped to such low values over Phanerozoic time that fires became impossible. Fossil charcoal, as evidence of paleofires, has been found for all times that trees have populated the land, and the lower limit for the production of charcoal has been estimated to be at about 13% O2 (28 <http://www.pnas.org/content/96/20/10955.full#ref-28> ). By contrast, the upper limit for O2 is in dispute. On the basis of experiments on the ignition of paper strips at different oxygen levels and fuel moisture contents, Watson et al. (27 <http://www.pnas.org/content/96/20/10955.full#ref-27> ) concluded that past levels of atmospheric O2 could never have risen above 25%. However, consideration of actual forest fires and the response of ecological disturbance to fires led Robinson (29 <http://www.pnas.org/content/96/20/10955.full#ref-29> ) to conclude that greater O2 variation might occur and that, at any rate, paper is not a good surrogate for the biosphere. In fact, Robinson states paleobotanical evidence for a higher frequency of fire-resistant plants during the Permo-Carboniferous, supporting the idea of distinctly higher O2levels at that time."
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