The Surprising Things Arctic Ice Can Tell Us About Human History
From the Dark Ages to Silicon Valley, the ice knows all.
One of the most unlikely keepers of humanity's history lies in the frozen Arctic. In a new study, scientists say that particles of lead trapped in ice in the north pole tell the story of commercial and industrial processes dating back to the Middle Ages.
As humanity has burnt fuel, sailed ships, made currency, prepared for war, and any number of countless actions, it has sent emissions into the air. In ancient days, these emissions could stem from mining and smelting iron for Roman coins. Man-made emissions in the modern day are infamous, they have helped create a situation of global warming that has begun to effect the climate disastrously.
Be they from the ancient Roman empire or modern day America, all of these lead particles would catch rides on wind currents that would take them to places like Greenland or the Arctic. Neither Greenland nor the Arctic have a lot of lead naturally, meaning that scientists looking at the lead today can safely assume they rode wind currents to get there. So when there was more trade, particle levels rose. When there was less—like, say, during the Black Plague—the levels fell.
Studying thirteen Arctic ice cores from Greenland and the Russian Arctic, researchers from the Desert Research Institute (DRI), the University of Oxford, the Norwegian Institute for Air Research, the University of Copenhagen, the University of Rochester, and the Alfred Wegener Institute for Polar and Marine Research looked at samples from 500 to 2010 C.E., a span of time covering massive change in humanity's condition. Their work has been published in the Proceedings of the National Academy of Sciences.
Their work expanded on a project some of scientists had done previously, which looked at a single ice core and a smaller time frame.
"We have extended our earlier record through the Middle Ages and Modern Period to the present," says Joe McConnell, Ph.D., lead author on the study and Director of DRI's Ultra-Trace Ice Core Chemistry Laboratory in Reno, Nevada, in a press statement. "Using an array of thirteen ice cores instead of just one, this new study shows that prior to the Industrial Revolution, lead pollution was pervasive and surprisingly similar across a large swath of the Arctic and undoubtedly the result of European emissions. The ice-core array provides with amazing detail a continuous record of European—and later North American—industrial emissions during the past 1,500 years."
The expanded team was necessary for their work. "Developing and interpreting such an extensive array of Arctic ice-core records would have been impossible without international collaboration," McConnell says.
The team found that lead concentration in all thirteen ice cores matched up with history. Increases were timed with new technologies and European expansion, decreases lined up with climate disruptions, wars, plagues, and famines.
"Sustained increases in lead pollution during the Early and High Middle Ages (about 800 to 1300 C.E.), for example, indicate widespread economic growth, particularly in central Europe as new mining areas were discovered in places like the German Harz and Erzgebirge Mountains," McConnell says. "Lead pollution in the ice core records declined during the Late Middle Ages and Early Modern Period (about 1300 to 1680 C.E.) when plague devastated those regions, however, indicating that economic activity stalled."
Even relatively modern Congressional legislation could be found in the lead levels.
"We found an overall 250 to 300-fold increase in Arctic lead pollution from the start of the Middle Ages in 500 C.E. to 1970s," explained Nathan Chellman, a doctoral student at DRI and coauthor on the study. "Since the passage of pollution abatement policies, including the 1970 Clean Air Act in the United States, lead pollution in Arctic ice has declined more than 80 percent."
But the modern era shouldn't pat itself on the back too much. "Lead levels are about 60 times higher today than they were at the beginning of the Middle Ages," Chellman added.
Some scientists today describe the modern era as the Anthropocene, a geologic period in which humanity has changed the nature of the planet.
"What we're finding is interesting not just to environmental scientists who want to understand how human activity has altered the environment," said Andrew Wilson, Ph.D., Professor of the Archaeology of the Roman Empire at Oxford and co-author on the study. "These ice-core records also are helping historians to understand and quantify the ways that societies and their economies have responded to external forces such as climate disruptions, plagues, or political unrest."
Greenland's ice holds many more secrets. Earlier this year, scientists found the second largest solar proton event in history in the ice, over 1,000 years ago.
Source: Desert Research Institute
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