Sulfur in Antarctic Snow Reveals Past Climate History of Our Planet: Earth was 'On Fire'

Sulfur discovered in the far reaches of the Antarctic may be telling scientists a bit more about the past history of our climate. Researchers have discovered sulfur signals in the snow which could actually reveal a bit more about what we might expect in the future.

The element, sulfur, can be found almost everywhere. It occurs in four stable forms, or isotopes; each of these isotopes has a slightly different mass. Ordinary reactions incorporate sulfur isotopes into molecules according to mass. Sometimes, though, sulfur divides different so that the relative ratios of the different isotopes are anomalous. That's why by measuring the direction and degree of that anomaly in layers of snow, researchers can learn more about a single season's snowfall.

In this case, the researchers sorted through chemical reactions that led to traces of sulfur in the Antarctic from the years 1984 to 2001. It turns out that eruptions of huge volcanoes, the disruptive pattern known as El Niño, and a fire season each left distinctive chemical marks in the layered snow near the South Pole.

By analyzing the sulfur, the researchers revealed a process, known but overlooked, that should actually be included in models of climate-both forecasts of climate to come and those of Earth's early history.

 "We observed huge signals from ENSO driven changes like extreme dry weather and ensuing biomass burning, which surprised me," said Robina Shaheen, one of the researchers, in a news release. "The pattern we saw fits signals that have been observed in pre-Cambrian rocks, which prompted us to take another look at which molecules play a role in this chemistry."

In the end, the researchers found that a series of volcanic eruptions probably cooled the climate in the years following. Then, there was an extreme ENSO which resulted in an odd spike of potassium. The dry season following caused large swathes of land to burn.

"Earth was on fire," said Mark Thiemens, one of the researchers. "The Amazon, central Africa, Australia, much of Indonesia, the whole middle of the planet, the tropics, heated."

The findings reveal how sulfur abnormalities can tell researchers a bit more about Earth's climate history. This, in turn, can inform future predictions about what our planet's climate may do in the future.

The findings are published in the journal Proceedings of the National Academy of Sciences.