History in Ice

(Dr. Nicole Spaulding, Climate Change Institute, University of Maine)

Colle Gnifetti glacier, Switzerland

Lead pollution levels from the Middle Ages preserved in an ice core taken from Colle Gnifetti glacier in the Swiss Alps reflect political upheaval in England, some 500 miles away, a multidisciplinary research team has found. In addition to studying archaeological data and tax records, the researchers used lasers to measure how lead levels in the core changed from year to year. They observed a major spike in lead pollution during the reign of the English Angevin kings—Henry II, Richard I, and John—between 1154 and 1216, when economic growth led to an increase in silver and lead production from British mines. Lead particles from the extraction and smelting processes were carried southeast by weather patterns, and traces of the metal were trapped in Swiss glaciers.

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