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The ocean floor of the South Pacific contains traces of ancient dust that may have changed the Earth’s own climate, and new research suggests it came from beneath the ice age glaciers of what is now Argentina.
Driven by strong westerly winds some 20,000 years ago, these microscopic minerals would have circumnavigated nearly the entire globe before finally coming to rest in the mid-latitudes of the Pacific.
Importantly, they carried a nutrient that could explain a global cooling period. That ingredient was iron.
Iron is a vital nutrient for the microscopic algae in our oceans, known as phytoplankton, and these creatures are themselves a key part of Earth’s climate.
This is because phytoplankton absorbs carbon during photosynthesis, thus storing atmospheric CO2 in our oceans and driving global cooling. They may even represent “the largest biological carbon sequestration mechanism on the planet”.
Today, iron still helps fertilize our oceans, but during the peak of Earth’s last ice age, much more iron-containing dust was unearthed during the seasonal melting of glaciers, which was blown into the ocean at a very fast rate. highest.
All of this extra iron fueled phytoplankton which then lowered CO2 levels in the atmosphere and could help explain “how the Earth could have gotten so cold at that time,” says Torben Struve, a geoscientist at Oldenburg University. in Germany.
Therefore, some scientists think iron fertilization could be a useful way to increase our oceans’ carbon sink and help cool our planet in the future.
But geoengineering of this kind is a risky and controversial strategy, and the results of this new study only show how much dust would be needed to have a big enough impact.
Today, human emissions have caused CO2 levels to rise from about 280 to about 415 ppm (parts per million) since the industrial revolution, a spike that is far above natural levels.
During the last ice age, however, previous models confirmed that iron-containing dust was responsible for reducing atmospheric CO2 by about 40 ppm.
That’s about half the natural variation between that ice age and the subsequent interglacial period, and not even a quarter of our emissions.
However, scientists are determined to learn more about this complex feedback system in the hope that it will someday improve our climate models or help us capture more atmospheric carbon.
Analyzing 18 sediment cores from the South Pacific Ocean between Antarctica, New Zealand and Chile, the new study compared the chemical footprints of ancient dust with geological data from different continents.
Ultimately, the results suggest that up to 80 percent of the iron-containing dust came from what is now northwestern Argentina – and probably came there from afar, traveling some 20,000 kilometers (12,400 miles) with powerful westerly winds during the last great ice age.
This is a unique and interesting discovery, because today the ingress of dust from Australian rivers and lakes dominates the entire study area.
Even in the past, Patagonia is usually considered the main source of ancient and distant dust, not regions further north of Central South America.
“[W]We were surprised to find that the sources and transport routes of the dust were completely different from today and even different from what we would have expected, ”says Struve.
“Global warming has changed winds and environmental conditions in the regions of origin.”
Even something as small as dust can have global repercussions. Thirty years after we first discovered its impact on the climate system, we are still learning more about these microscopic minerals, including where they come from.
The study was published in Nature Communications.
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