Video | Business Headlines | Internet | Science | Scientific Ethics | Technology | Search

 


Adding Iron To Oceans Not Effective - Study

19 March, 2004

Adding Iron To ‘Anaemic’ Oceans Not Effective In Battle Against Global Warming, Study Finds

Iron fertilisation of microscopic plants in the surface ocean may not be the answer to removing excess “greenhouse gas” carbon dioxide from the atmosphere, according to a paper published by Nature and released on-line yesterday.

The results of experiments in the Gulf of Alaska, led by University of Otago-based oceanographer Dr Philip Boyd, show that iron is not the only factor in the carbon cycle equation. Silicate is also key to the blooming of microscopic plants (phytoplankton) in the sea and the corresponding fixing of carbon – a discovery which may rule out the possibility of fertilising the “ocean deserts” of the world in a bid to offset increased levels of carbon dioxide in the atmosphere.

Almost half the Earth’s photosynthesis is carried out by phytoplankton in the sea. These tiny cells harvest sunlight to fix carbon which is then either re-mineralised to carbon dioxide in the surface waters of the ocean and released back into the atmosphere, or “pumped” down to the deep ocean layer as the plankton sink into the abyss. The strength of this biological pump plays a key role in regulating our climate. In parts of the world where the surface ocean is lacking in iron, phytoplankton are anaemic and therefore are unable to make use of the available nutrients. This means the ocean’s potential to regulate our climate is not being fully realised.

An earlier experiment carried out in the Southern Ocean in 1999 by Boyd and a team of New Zealand and international scientists -- where around 8,000 kg of an iron compound in solution was distributed over a patch of ocean eight km in diameter -- had such dramatic results (a five-fold increase in phytoplankton stocks during the developing bloom), it was thought that simply adding iron might be the answer to increasing the amount of atmospheric carbon dioxide locked up in the ocean.

“What we found, however,” says Boyd, “is that adding iron to the ocean produces a very different picture in the longer-term.” After 18 days of a similar experiment in the Gulf of Alaska, the iron-induced bloom declined and satellite pictures show merely a ghost of the plankton-rich patch that blossomed initially. “We think the decline was initiated by the drop-off in iron levels, but the secondary factor is the removal of all of the silicate by phytoplankton. Until now, we had not realised the importance of silicate in causing the bloom’s decline,” he says.

“And while it might be feasible for us to add iron to the ocean to stimulate blooms, for every ton of it we throw overboard, we’d need to add at least 5000 tons of silicate to enable the blooms to persist for long enough to impact on atmospheric carbon
dioxide levels. It’s just not practical.”

The other important implication of this work is the significance of silicate supply to climate change in the geological past. “We have been pointing to increased natural supplies of iron (from atmospheric dust) as being responsible for decreases in atmospheric carbon dioxide in the distant past, but this new evidence suggests that natural supplies of silicate must also have been greater at the same time.”

During the bloom initiated in the Gulf of Alaska waters, sediment traps (underwater particle collectors) were also deployed below the bloom at various depths to determine how much of the carbon fixed by the bloom sinks to into the subsurface ocean layer. This small but significant transfer of carbon is the key transfer mechanism involved in the climate regulating process.

Most of the carbon ‘pumped’ to these deep waters via sinking particles is re-mineralised back to carbon dioxide by bacteria, just as it is in the surface layer, but the difference is, it remains here for extremely long time periods – on average, this atmospheric carbon dioxide is locked up for 1000 years.

“With these underwater rain gauges in place below the iron-enriched area and outside it, we could determine whether adding iron helps more carbon to settle to depth and therefore increases the efficiency of operation of the pump,” says Boyd. “Our experiment showed that only an additional 10 per cent of the carbon fixed by phytoplankton following iron enrichment of surface waters actually settled to depth.

“The fact that we were not able to significantly improve the efficiency of this transfer of carbon below the surface waters strengthens the argument that adding iron to the ocean is not going to be an effective mitigating strategy for atmospheric CO2 levels thought to be increasing global warming.”

ENDS

© Scoop Media

 
 
 
 
 
Business Headlines | Sci-Tech Headlines

 

Half Full: Dairy Payouts Steady, Cash Will Be Tight

Industry body DairyNZ is advising farmers to focus on strong cashflow management as they look ahead to the 2015-16 season following Fonterra's half-year results announcement today. More>>

ALSO:

First Union: Cotton On Plans To Use “Tea Break” Law

“The Prime Minister reassured New Zealanders that ‘post the passing of this law, will you all of a sudden find thousands of workers who are denied having a tea break? The answer is absolutely not’... Cotton On is proposing to remove tea and meal breaks for workers in its safety sensitive distribution centre. How long before other major chains try and follow suit?” More>>

ALSO:

Scoop Business: NZ-Korea FTA Signed Amid Spying, Lost Sovereignty Claims

A long-awaited free trade agreement between New Zealand and South Korea has been signed in Seoul by Prime Minister John Key and the Korean president, Park Geun-hye. More>>

ALSO:

PM Visit: NZ And Viet Nam Agree Ambitious Trade Target

New Zealand and Viet Nam have agreed an ambitious target of doubling two-way goods and service trade to around $2.2 billion by 2020, Prime Minister John Key has announced. More>>

ALSO:

Scoop Business: NZ Economy Grows 0.8% In Fourth Quarter

The New Zealand economy expanded in the fourth quarter as tourists drove growth in retailing and accommodation, and property sales increased demand for real estate services. More>>

ALSO:

Scoop Business: RBNZ’s Wheeler Keeps OCR On Hold, No Rate Hikes Ahead

The Reserve Bank has removed the prospect of future interest rate hikes from its forecast horizon as a strong kiwi dollar and cheap oil hold down inflation, and the central bank ponders whether to lower its assessment of where “neutral” interest rates should be. The kiwi dollar gained. More>>

ALSO:

Get More From Scoop

 
 
 
 
 
 
 
 
 
Sci-Tech
Search Scoop  
 
 
Powered by Vodafone
NZ independent news