A time when Earth was nearly free of icy glaciers and alligators could be found crawling in northern Greenland has been giving scientists insight into what the planet could see in the not-too-distant future.
Tim White, a senior researcher in the Earth and Environmental Systems Institute in Penn State’s College of Earth and Mineral Sciences, along with Cecilia del Papa from the National University of Cordoba in Argentina, has been heading to the eastern Andes Mountains each year since 2006. This year, they were joined by colleagues from the University of Zaragoza in Spain.
There, the researchers sift through layers of ancient soils that were weathered from sediments in the basin and turned to rock before, during and after the time known as the Paleocene-Eocene Thermal Maximum, approximately 55 million years ago.
“A lot of the other times when the Earth was warm, the rate at which it got warm was over many millions of years, whereas this was almost instantaneous,” White said of the drastic temperature shift at the PETM. “The planet warmed up significantly at a time when there was little or no ice on Antarctica and probably very few glaciers in the mountains.”
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Well-preserved layers in the 10,000-foot-high landscape in Argentina offer not only a look at what was happening on Earth 55 million years ago, but also give scientists a chance to study a phenomenon that may be comparable to the warming conditions that are happening on Earth now.
“The reason it’s a good analogy is that the rate at which humans are currently warming the atmosphere is more or less the same as the rate that it had happened naturally 55 million years ago,” White said.
“This may be the best analogy to where the planet will be headed 500 to 1,000 years from now.”
To study that, the researchers collect and analyze “aridisols” — the ancient dryland soils similar to modern soils that developed in northern Mexico, Texas and other places where today 5 to 10 inches of rain a year is normal. The researchers are looking for answers about the period approximately 55 million years ago when conditions — and soils — abruptly switched from dry conditions to ones that were extremely wet and tropical, then back to dry again.
That global disturbance, White explained, led to changes in the carbon cycle of many things, including bits of leaves and other plant material that have been preserved in the layers of rock in the Andes.
“It records this moment when there was a big change in the carbon cycle and the values change quite abruptly,” he said. “That happened all over the planet at this period of time.”
The aim is to get more precise dates for when those ancient soils formed along the banks of streams and rivers before the climate changed, moving both the sediments and streams in the Salta Basin of northwest Argentina around during this tropical period. Getting a more precise date stamp will allow scientists to get a narrower time frame for when and how fast the warming took place and offer insight into what to expect in the future.
Date stamping can be done for samples collected in places constrained on either side by a variety of means, including age dating of volcanic ash beds. But those volcanic ash beds aren’t found in the Salta Basin. Instead, White and the other researchers compare samples from the organic matter found in the Andes Mountains with samples from other areas that have already been date stamped.
“It’s like a bar code in the grocery store,” he said. “It’s a carbon isotopic signature that’s unique and distinct in this time period.”
Similar research has been done in other mid-latitude places, but the focus for this project is on the subtropical realm closer to the equator. Known as the Maiz Gordo Formation, the area of focus is a layer of rock literally preserved through time. The researchers have been going there, excavating rock samples that are then processed in a mass spectrometer at Penn State. The spectrometer produces the carbon isotope signature, which can provide a sort of fingerprint of the samples.
Those findings, in turn, provide more refined information for scientific modeling to see what turn the Earth is likely to take by providing data to simulate the Earth’s climate.
“If, as a society, we want to begin to really face what it is we’re doing to the planet, we need to understand the past,” White said.
Funding for the project came from the U.S. Geological Survey, National Science Foundation and American Chemical Society.