Thursday, April 21, 2016

Taiwanese Scientists Cast Doubt on "Iron Hypothesis"

John H. Martin
“Give me a half tanker of iron,
and I will give you an ice age.”
Said John H. Martin, one of the great oceanographers of my age. His hypothesis was that in areas of the ocean with "high" nutrient concentrations and low chlorophyll (HNLC areas), like much of the Pacific, iron was the limiting nutrient, and that adding iron could stimulate oceanic primary. In another link, stimulating primary production would increase the rate of sedimentation of the fixed carbon produced by the phytoplankton, and remove some carbon dioxide from the atmosphere, offsetting or even reducing atmospheric CO2 and offset or even reverse global warming. He didn't really propose to set off a new ice age.

A lot of experiments were carried out to test "the iron hypothesis." It worked sometimes, and it didn't work sometimes. Biology is like that. It's not as straightforward as rocket science. New studies by Taiwanese researchers also find that iron fertilization was not always effective:

Taiwanese researchers have poured cold water on the possibility of capturing carbon with artificial algae blooms, created by fertilising the oceans with iron. The problem appears to be that the artificial algae bloom depletes other essential ocean nutrients, causing a reduction in algae growth elsewhere in the ocean.

To alleviate the impact of global warming, scientists have proposed a hypothesis of “iron fertilization,” assuming that adding iron into the ocean can boost the growth of algae to absorb the carbon dioxide in the air.

However, researchers in Taiwan have found flaws in this hypothesis.
Working with Columbia University, a NTU research group led by Haojia Abby Ren, associate professor of Geosciences at National Taiwan University (NTU), has poured iron into 12 waters around the globe to perform experiments on the “iron fertilization” hypothesis. It turned out algae only thrives in one-third of the areas tested.
The growth of algae requires nutrients other than iron, such as nitrate and phosphate. With the growing amount of algae, consumption of these nutrients also increases in the area. But when currents carry the algae to other waters, the nutrients become relatively scare elements, making algae hard to grow.
Read more:

This claim is backed by an earlier study, which suggests that increased iron outflows into the ocean during the last ice age, caused by glaciers scraping iron rich minerals into the sea, did not increase algae growth in equatorial regions, because increased algae growth in subantarctic zones depleted other ocean nutrients.
One third of the ocean is a lot of ocean . . .

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