Did New Zealand Dust Influence the Last Ice Age?
In something as tiny as a speck of dust lies the potential to change earth’s climate. When winds blow iron-rich dust off the continents, they give the plant-like algae floating on the surface of the oceans added nutrients to grow faster. Large algal blooms can draw down carbon from the atmosphere, and in extreme cases, cool earth’s climate. Researchers are trying to understand to what extent dust, by providing extra food for algae, or phytoplankton, may have helped to tip the planet into a deep freeze starting about 30,000 years ago. From the onset of the last ice age to its peak, about 18,000 years ago, carbon dioxide levels fell by about 100 parts per million. As much as 25 percent of that drop can be attributed to the effect of dust.
In January, Bess Koffman, a postdoctoral researcher at Lamont-Doherty Earth Observatory, traveled to the rugged mountains of New Zealand’s South Island to collect dust. She wasn’t looking for any old dust; rather, her mission was to find dust that had been pulverized by the massive glaciers that covered much of the South Island during the last ice age. Dust ground-up by glaciers contains iron that’s as much as a hundred times more soluble than iron found in older dust blown in from places like Australia. Phytoplankton have an easier time digesting glacial dust, potentially creating a bigger effect on the carbon cycle.
Koffman is testing the idea that iron-rich sediments from New Zealand were a significant source of dust to the southern Pacific Ocean during the last ice age, challenging the view that Australia supplied most of it. Working with Lamont glacial geologist Michael Kaplan, geochemists Steven Goldstein and Gisela Winckler, and Cornell climate modeler Natalie Mahowald, Koffman is comparing dust samples from New Zealand and Antarctica with other potential dust-source continents, such as Australia, South America, and Africa. In the photo essay above, she explains how she collected the dust, what analysis looks like in the lab and what she hopes to learn.