Thursday, February 19, 2015

Secrets of the Deep

Fig.1. The National Ice Core Laboratory holds 17,000 meters of ice cores from Antarctica, Greenland, and North America. The typical tube contains a one meter ice core section (Credit: Eric Cravens, National Ice Core Lab, USGS)

During the early morning hours of July 16, 1945, an atomic bomb was detonated for the first time ever. This test, completed in a remote corner of New Mexico by scientists with the U.S. Army, marked a significant point in human history. One study contends that this date is the beginning of the Anthropocene, while others believe that the “Age of Humans” may stretch back to around 10,000 years ago with the advent of agriculture. A recent study, however, hopes that work with ice cores may help to inform this debate, as well as show how humans affect the world around them.

Pre-industrial pollution

Researchers at Ohio State University uncovered evidence of pollution due to human activities from more than four hundred years ago. Their work brought them to the Quelccaya Ice Cap in southern Peru, where the ice record stretches back 1,200 years. This time span allowed co-author Lonnie Thompson and his team to draw out an ice core that would show environmental conditions before and after the industrial revolution.

They found that a portion of the core dated from the 16th to 19th centuries contained surprising spikes in metal compounds, such as lead. This specific chemical signature in the ice matched that of silver mines over 500 miles away in what is now Bolivia. Thompson et al. believe that chemical byproducts from intensive silver mining during those centuries were blown by wind to the northwest where they settled and were trapped in ice.

Unfortunately, ice laced with pollution from distant lands is not specific to the Quelccaya Ice Cap. Ice records show lead pollution from both ancient Greek and Roman mining as well as from modern times. Thompson hopes that evidence of pre-industrial pollution might add our understanding of the timeline of human activities and their impact on the environment.


Pollutants and climate change

Ice cores are a unique medium to quantitatively study environmental changes over thousands of years. In addition to capturing pollutants from human activities, air bubbles, fossils, and organic traces can also be frozen in time. One example is evidence of boreal biomass burning during the 1600s in Central Asia. An extremely dry period in Asia caused an increase in fires, which released pollutants into the atmosphere. Smoke plumes and wind transported these compounds all the way to Greenland where they became trapped within ice. Just as in Greenland, environmental changes on one continent can affect another.

Although the Anthropocene may have a disputed start date, ice core collections tell a stark tale about pollution and climate change. In the past 800,000 years, atmospheric CO2 levels have never been higher and pollution continues to be a problem. Repositories, such as the U.S. National Ice Core Laboratory, hold thousands of meters worth of ice cores chronicling hundreds of thousands of years. Between chemical or isotopic tests and analyzing air bubbles, scientists can recreate the world’s environmental history. With the implementation of new technologies to collection studies, they can continue to unlock new secrets from ice cores and advise on a better future for the Anthropocene.


Biello, D. (2015, February 10). Nuclear Blasts May Prove Best Marker of Humanity’s Geologic Record [in Photos]. Scientific American. Retrieved from

British Antarctic Survey. (2015). Ice cores and climate change. Natural Environment Research Council Briefings. Retrieved from

Fischer, H., Schmitt, J., Eggleston, S., Schneider, R., Elsig, J., Joos, F., Leuenberger, M., Stocker, T.F., Köhler, P., Brovkin, V., & Chappellaz, J. (2015, January). Ice core-based isotopic constraints on past carbon cycle changes. Pages Magazine, 23 (1): 12-13. Retrieved from

Gorder, P.F. (2015, February 9). Earliest evidence of large-scale human-produced air pollution in South America found [Press release]. Ohio State University press. Retrieved from

Kehrwald, N., Zennaro, P., Schüpback, S., Kirchgeorg, T., McConnell, J.R., Zangrando, R., Gambaro, A., & Barbante, C. (2015, January). Two thousand years of boreal biomass burning recorded in the NEEM ice cores. Pages Magazine, 23 (1): 14-15. Retrieved from

National Ice Core Laboratory. (n.d.) About NICL. Retrieved from

Zielinski, S. (2015, February ). Spanish Conquest of the Incas Caused Air Pollution to Spike. Smithsonian Magazine. Retrieved from


A proposed epoch that began when human activities had a significant impact on the globe’s environment and ecosystems.
ice core
Cylinders of ice drilled out of glaciers or an ice cap.

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