Professor joins international research team studying the impact of dust and iron input to the Pacific Ocean

Apr 13, 2016

Dr. Franco Marcantonio (Robert R. Berg Professor in Geology) recently joined an international team of scientists to study samples taken from the Pacific Ocean that analyzed the impact of iron delivered in dust to the Pacific Ocean thousands of years ago.  Their work is published in the journal, Nature.

In the harsh conditions of the previous ice age, which consisted of colder and windier weather, large amounts of dust containing iron were scattered from land into the ocean.

The purpose of the study focused on whether the increase in iron supplied to the Pacific Ocean produced more carbon-sequestering phytoplankton to take in CO₂ from the Earth’s atmosphere, potentially creating conditions for a cooler climate.

“We proved it was dustier – but was there more photosynthetic production to to help lower CO₂? We looked at the chemistry of the sediments, and concluded that there was not more productivity, at least for this area of the world’s ocean”, says Dr. Marcantonio.

However, he and other scientists believe an increase in iron did lead to an increased growth of phytoplankton in other locations, such as the ocean surrounding Antarctica.

“Iron can only fertilize if there are major nutrients (such as nitrogen and phosphorus) available”, he explains.

“It turns out there was more dust in the Southern Ocean (off Antarctica) during the last ice age about 20,000 years ago, and there was a lot more productivity there as a consequence. Because of the increased iron supply, most of the major nutrients were depleted. As a result, these waters, which are ultimately the source for waters upwelled in the equatorial Pacific, were already devoid of their nutrients.”

So while it was dustier, and extra iron was being delivered to the Pacific, the study found the lack of nitrogen and phosphorus limited phytoplankton growth in that region.

Dr. Marcantonio was joined by colleagues from Columbia University, Princeton University, the University of California-Santa Cruz, and National Taiwan University.

By: Andrew Vernon '06