An interdisciplinary team of experts led by the Desert Research Institute has used ice core records from the Greenland ice sheet to learn more about ancient European civilizations.
During the height of the ancient Greek and Roman empires thousands of years ago, lead emissions drifted from Europe and settled into Greenland’s ice almost 3,000 miles away.
The scientists used ice samples from the North Greenland Ice Core Project (NGRIP) to measure, date, and analyze European lead emissions that were captured in the ice between 1100 BC and 800 AD.
“Our record of sub-annually resolved, accurately dated measurements in the ice core starts in 1100 BC during the late Iron Age and extends through antiquity and late antiquity to the early Middle Ages in Europe – a period that included the rise and fall of the Greek and Roman civilizations,” said study lead author Dr. Joe McConnell.
“We found that lead pollution in Greenland very closely tracked known plagues, wars, social unrest and imperial expansions during European antiquity.”
The researchers obtained more than 21,000 precise lead and chemical measurements to develop a continuous record for the 1,900-year time period.
“We believe this is the first time such detailed modeling has been used to interpret an ice-core record of human-made pollution and identify the most likely source region of the pollution,” said study co-author Dr. Andreas Stohl.
The team used advanced atmospheric transport model simulations to determine the magnitude of European emissions from the lead pollution levels measured in the ice. Most of the lead emissions observed in the study are likely linked to the production of silver, which was a key element of currency.
“Because most of the emissions during these periods resulted from mining and smelting of lead-silver ores, lead emissions can be seen as a proxy or indicator of overall economic activity,” explained Dr. McConnell.
The research team explored the ice record for connections between lead emissions and significant historical events.
The highest sustained levels of lead pollution emissions were found to coincide with the height of the Roman Empire, known as the Pax Romana, during the 1st and 2nd centuries AD. Lead emissions were found to be very low during the last 80 years of the Roman Republic, a period known as the Crisis of the Roman Republic.
“The nearly four-fold higher lead emissions during the first two centuries of the Roman Empire compared to the last decades of the Roman Republic indicate substantial economic growth under Imperial rule,” said co-author Professor Andrew Wilson.
The ice record demonstrated that lead emissions fluctuated along with wars and political instability, particularly during the Roman Republic. The emissions took notable dives when two major plagues struck the Roman Empire in the 2nd and 3rd centuries.
“The great Antonine Plague struck the Roman Empire in AD 165 and lasted at least 15 years. The high lead emissions of the Pax Romana ended exactly at that time and didn’t recover until the early Middle Ages more than 500 years later,” explained Professor Wilson.
The research team was comprised of ice-core specialists, atmospheric scientists, archaeologists, and economic historians.
“Working with such a diverse team was a unique experience in my career as a scientist,” said Professor McConnell. “I think that our results show that there can be great value in collaborating across disciplines.”
The research is published in the journal Proceedings of the National Academy of Sciences.
By Chrissy Sexton, Earth.com Staff Writer