14 January 2008

Ocean Phytoplankton and Climate Interactions

Posted by John Freeland

“Give me a half a tanker of iron, and I’ll give you the next ice age.” – John Martin, Oceanographer

For over a decade, fertilizing the oceans with iron, an important plant nutrient, to create algal blooms has been proposed and demonstrated as a way to capture atmospheric carbon and mitigate global warming.  The carbon-rich algae, or phytoplankton, grow, die, and sink to the ocean bottom where the carbon is stored, or “sequestered.” At least nine ocean-going iron enrichment experiments have been done thus far and the process works.

A NASA satellite image of an algal bloom about 100-miles (150km) created by one iron enrichment experiment is shown here.

Sattelite image of ocean algal bloom (NASA)

Photo source: NASA and CSA

But it turns out the phytoplankton have still another strong environmental effect: the production of cloud-seeding aerosols.

Evidence shows as the wind sweeps these materials up from ocean waves rich in phytoplankton, the effect is enhanced cloud formation and increased albedo, which reflects solar radiation back out to space.

Does this offer at least a partial fix for global warming? Iron’s cheap and relatively abundant. It could be spread around the ocean on a large scale. The thought of manipulating ocean ecosystems undoubtdedly makes some people nervous, including me. Common sense would go against the notion of fixing one problem by creating another. Then again, we seem to have no problem drastically altering the earth’s land surface through deforestation, agriculture, and urbanization.

But, given that the ocean is 71% of the earth’s surface and probably the primary regulator of earth’s climate, we better be careful with it.