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Images: Fertilizing the Ocean with Iron

The brilliant swirls of green and blue in the midst of the deep, blue Atlantic Ocean off Argentina were created by multitudes of tiny marine plants (phytoplankton) that draw carbon dioxide from the atmosphere to grow. Intentionally adding iron to the ocean would fertilize more phytoplankton blooms. Could this help reduce the buildup of greenhouse gases? (Image courtesy of NASA)

A plume of dust from Alaskan glacial sediments blows far into the Pacific Ocean. Storms like this, or from vast deserts such as the Sahara, are the natural way that iron gets into oceans to fertilize phytoplankton blooms. (NASA image courtesy Jeff Schmaltz, MODIS Rapid Response Team, Goddard Space Flight Center)

Iron fertilization experiments can set off blooms that are visible from space. In the bottom center of the satellite image above, note the red patch (indicating high levels of chlorophyll) from the Subarctic Ecosystem Response to Iron Enrichment Study in 2002. (Image provided by Jim Gower, Bill Crawford, and Frank Whitney, Institute of Ocean Sciences, Sidney BC.)

Scientists aboard the Australian research vessel Aurora Australis studied the natural cycling of iron in the Southern Ocean in 2001. Ken Buesseler, a marine chemist at Woods Hole Oceanographic Institution, was aboard that expedition, and in 2002 he served as chief scientist of the Southern Ocean Iron Experiment (SOFeX). The three-ship operation added iron to stimulate a phytoplankton bloom in the Southern Ocean and investigated the results. (Photo by Ken Buesseler, Woods Hole Oceanographic Institution)

(Data courtesy of NASA SeaWiFS Project.)

Phytoplankton blooms draw down carbon dioxide from the atmosphere. They are eaten by zookplankton, which produce pellets and aggregates of carbon-containing fecal matter (above), which sink into the depths, where carbon can be sequestered from the atmosphere. How much carbon would actually be sequestered via ocean iron fertilization is an open question.

Underlying proposals to add iron to the ocean as a means to mitigate climate change is the brutal fact that atmospheric carbon dioxide levels have increased precipitously since the 1850s and continue to rise. CO2 levels for the past 1,000 years were derived from ice cores. The inset shows direct atmospheric CO2 observations from Mauna Loa, Hawaii, beginning in 1958. (Adapted from Sarmiento & Gruber. Inset: from C.D. Keeling and the National Oceanic and Atmospheric Administration Climate Monitoring and Diagnostics Laboratory)

Debating the pros and cons of ocean iron fertilization at a panel at the WHOI conference are (left to right): Elizabeth Kim of the U.S. Environmental Protection Agency; Lisa Speer of the National Resources Defense Council; and Margaret Leinen of Climos Inc. (Photo by Tom Kleindinst, Woods Hole Oceanographic Institution)

The Ocean Iron Fertilization conference, which drew a variety of stakeholders in the debate, was organized by (left to right) WHOI marine chemist Ken Buesseler, Hauke Kite-Powell, a researcher at the WHOI Marine Policy Center, and WHOI marine chemist Scott Doney. (Photo by Tom Kleindinst, Woods Hole Oceanographic Institution)