Fertilisation test: Image shows a drifting sediment trap called PELAGRA used by the CROZEX mission to collect samples of sinking algal material at 150 m depth.
Credit: R T Pollard
The rest, though, will be recycled in the midwater region or, in the lower depths, eventually get pushed to the surface by deep ocean currents, which would prompt them to surrender their carbon, he explained.
This overturning takes place on a time scale of decades to a couple of hundred years, meaning the carbon would be stored out of harm's way for a long while but not permanently.
Massive underestimate
The study said carbon sequestration around the Crozet islands fell massively short – by 15 to 50 times – of some geo-engineering estimates, although it was also 20 times more than that calculated for a fertilisation experiment called SERIES.
These findings have "significant implications" for claims for ocean fertilisation, it said.
Around a dozen experiments in ocean fertilisation have been carried out, but the data they have yielded is often sketchy and contradictory. The experiments are complex and difficult to carry out and often do not look at the long-term effectiveness.
Some oceanographers, looking at published data, contend the sequestration yield is so poor that iron would have to be dumped over vast areas to make any inroad into the greenhouse-gas problem.
This would make the technique commercially unviable in addition to posing unknown risks for marine ecology, they say.
Carbon
Looks like they are going to have to go back to the old drawing board!
RT