Glacial ice cores are mile-long cylindrical columns of layered ice that are drilled out of the thickest parts of ice sheets from places like Greenland or Antarctica. Glacial ice cores are fascinating feats of human scientific and technologic achievement and they’re highly-detailed collection of environmental information too. A recent study has been able to see the rise and fall of the Roman Empire by studying the ancient climate by studying ice cores. How cool is that? Ice cold, of course. This brings up today’s big question: How can ice cores tell us about human history? Listen to this Question Your World radio report produced by the Science Museum of Virginia to find out.
Studying the atmosphere is not a new practice. In fact studying ice cores has told us a lot of important information about what the Earth’s past was like in terms of atmospheric information. For example, the air that gets trapped into tiny bubbles in the ice has been used for decades to measure the amount of heat-trapping gases like carbon dioxide that was in our atmosphere as far back as 2.7 million years ago. Spoiler alert: there’s more in our atmosphere today than back then!
Now, scientists have fingerprinted something else within the ancient ice from Greenland – a nearly year-by-year economic history of the rise and fall of the Roman Empire. Only thing is, this story isn’t written down in Latin and numerals…instead, the scientists had to read levels of Lead pollution! As the romans expanded and grew their empire they needed more and more silver. After all a growing empire will need more coins, weapons, house hold items, and so on. The Romans would mine silver from surrounding areas and then process the metal at high temperatures to make their needed items. In turn this process was the source for the airborne lead. As the empire grew and prospered their economy was healthy enough to continue these mining operations, thus being periods where there were higher amounts of lead put into the atmosphere. During times of hardship the mining operations were reduced and subsequently so were the emissions of lead. These varying amounts of particles were then stuck to snow as it fell and would become trapped in time in these glaciers.
In 2018, these ice cores were studied and the lead levels were observed. While lead levels are not a direct indicator of their GDP, they do seem to follow the ups and downs of the Roman Empire’s history though. During times of peace lead levels are seen to rise and during times of civil war or plagues they say the levels dip. So, to sum it up, Roman mining and extraction of silver used for coins and weaponry sent Lead particles into the atmosphere where they stuck to falling snow that built up in Greenland over several thousands of years. Here the annual cycles of melt and new ice are recorded in layers like a stack of flapjacks, with the older stuff at the bottom.
This allows scientists to now analyze the ice for Lead pollution and keep track of the economic ongoings of the Romans! Lead levels in the ice varied as the Romans founded and expanded their empire, fought major wars, and suffered from plagues and invasions and so on. Regardless it was the human activity of mining silver ore and smelting it for practical use that that allowed for detectable amounts of Lead to be added to the atmosphere.
This is just another way that the Earth has kept track of human history and how we have impacted the Earth system. Guess you can say studying the ancient climate really lead us to the discovery!