The Iron Experiments
Richard Barber's Team Goes to the End of the Earth to See
if Dust Once Played a Role in Climate Change p.2
Through nature’s own photovoltaic
process, called photosynthesis, these phytoplankton use sunlight
to break down and assimilate carbon dioxide that has found
its way to the plants from the air above, converting the gas
into plant sugars. Scientists, who call that process “fixing”
carbon, say the amount of resulting plant growth and proliferation
is limited in the Southern Ocean by the inadequate natural
availability of other nutrients—notably iron.
Further complicating the picture,
an expedition by New Zealand researchers confirmed just a
few years ago that the Southern Ocean is subdivided into zones
of high dissolved silicon to the south and low dissolved silicon
to the north. In the low silicon area fewer phytoplankton
naturally take the form of diatoms, marine plants that are
encased in silicon shells.
Barber says the New Zealanders’
findings were important because diatoms are considered the
most likely phytoplankton forms to sequester assimilated carbon
dioxide long enough for their remains to carry the carbon
remnants deep below the surface after death.
Resolving whether marine plants
could remove lots of atmospheric CO2 to indefinite
ocean cold storage if they were “fertilized” with natural
iron in the form of dust is the major goal of what have been
dubbed the “Iron Experiments.”
These experiments are designed to
address the Iron Hypothesis first proposed by the late John
Martin, an oceanographer at Moss Landing Marine Laboratories
in California, who died in 1993 before he could test the idea.
Martin’s ideas were rooted in research
suggesting that airborne dust during dry climatic periods
may have seeded iron-poor ocean waters, especially the Southern
Ocean area, with extra amounts of the metal, removing enough
atmospheric CO2 to cause the global cooling associated
with past ice ages. Other evidence suggests that CO2
levels then were substantially lower than today’s.
The hypothesis came in the 80s when
scientists were becoming attuned to evidence that human activities
were introducing strikingly more CO2 into the atmosphere,
where the gas could trap extra amounts of solar heat much
like a greenhouse does. Many scientists now agree that this
“greenhouse effect” already is causing global warming.
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