At the end of the last Ice Age, as the world began to warm, a swath of the North Pacific Ocean came to life. During a brief pulse of biological productivity 14,000 years ago, this stretch of the sea teemed with phytoplankton, amoeba-like foraminifera and other tiny creatures, who thrived in large numbers until the productivity endedas mysteriously as it beganjust a few hundred years later.
Researchers have hypothesized that iron sparked this surge of ocean life, but a new study led by Woods Hole Oceanographic Institution (WHOI) scientists and colleagues at the University of Bristol (UK), the University of Bergen (Norway), Williams College and the Lamont Doherty Earth Observatory of Columbia University suggests iron may not have played an important role after all, at least in some settings. The study, published in the journal Nature Geoscience, determines that a different mechanisma transient "perfect storm" of nutrients and lightspurred life in the post-Ice Age Pacific. Its findings resolve conflicting ideas about the relationship between iron and biological productivity during this time period in the North Pacificwith potential implications for geo-engineering efforts to curb climate change by seeding the ocean with iron.
"A lot of people have put a lot of faith into ironand, in fact, as a modern ocean chemist, I've built my career on the importance of ironbut it may not always have been as important as we think," says WHOI Associate Scientist Phoebe Lam, a co-author of the study.
Because iron is known to cause blooms of biological activity in today's North Pacific Ocean, researchers have assumed it played a key role in the past as well. They have hypothesized that as Ice Age glaciers began to melt and sea levels rose, they submerged the surrounding continental shelf, washing iron into the rising sea and setting off a burst of life.
Past studies using sediment coreslong cylinders drilled into the ocean floor that of
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Woods Hole Oceanographic Institution