Ancient dust from the depths of the ocean can help keep the last ice age cool

There are traces of ancient dust at the bottom of the South Pacific Ocean that has changed the Earth’s atmosphere, and new research suggests it came from beneath Argentina’s ice-age glaciers.

Wrapped by heavy westerly winds about 20,000 years ago, these microscopic minerals would have circulated almost all over the world before finally resting in the mid-latitudes of the Pacific.

Importantly, they kept a nutrient that could explain the period of global cooling. That component was iron.

Iron is an important nutrient for microscopic algae in our oceans, known as phytoplankton, and these organisms are an integral part of the Earth’s atmosphere.

Because phytoplankton absorb carbon during photosynthesis, it stores atmospheric CO2 in our oceans and causes global cooling. They could also represent “the largest biocarbon sequestration mechanism on the planet.”

Iron still helps fertilize our oceans today, but during the peak of Earth’s last ice age, much more iron-containing dust was found during seasonal glacier melting, and it was blown into the ocean at much higher rates.

All of this extra iron-fed phytoplankton lowered CO2 levels in the atmosphere and could help explain “how the Earth could be so cold at that time,” says Torben Struve, a geologist at the University of Oldenburg in Germany.

Thus, some scientists believe that iron fertilization could be a useful way to increase the carbon sink of our oceans and help cool our planet in the future.

But this type of geoengineering is a risky and controversial strategy, and the results of this new study show how much dust will be needed to have a large enough impact.

Today, after the Human Industrial Revolution, CO2 levels have risen from about 280 to 415 ppm (parts per million) due to human emissions – a surface well above natural levels.

During the last ice period, however, previous models have confirmed that about 40 ppm. Iron-bearing dust was responsible for drawing atmospheric CO2 through.

That’s about half the natural difference between the Ice Age and the following international period, and not even a quarter of our own emissions.

However, scientists have decided to learn more about this complex reaction system in the hope that it may one day improve our climate models or help us get more atmospheric carbon.

Analyzing 18 sedimentary cores of the South Pacific Ocean between Antarctica, New Zealand and Chile, the new study compares the chemical fingerprints of ancient dust with geological data from many different continents.

Finally, these findings suggest that as much as 20% of the iron-containing dust now comes from northwestern Argentina – and that it may have traveled farther and farther from there, traveling about 60,000 kilometers (12,400 miles) during the last westerly winds. . The main ice age.

It is a unique and interesting discovery, because today, the input of dust from the rivers and lakes of Australia dominates the entire study area.

Even in the past, Patagonia was generally considered to be the main source of ancient dust, not far north in Central South America, but far-traveled.

“[W]E was surprised to learn that the dust sources and transport routes were completely different from today and even different than we expected, ”says Struve.

“Global warming has led to changes in wind and environmental conditions in the resource regions.”

As small as dust can have global consequences. Thirty years after we first discovered its effect on the climate system, we will still learn more about these microscopic minerals, where they came from.

The study was published in Nature Communications.