Ice high in the Alps has preserved a surprising record of medieval industry, showing that pollution from mining and metalworking left a measurable mark on the atmosphere long before the modern age.
In a new study published in Frontiers in Earth Science, researchers analysed an ice core taken from the Weißseespitze glacier on the Austrian–Italian border. Stretching nearly ten metres down to bedrock, the core captures a continuous environmental record spanning from the Roman period to the early modern era.
“These remarkable climate archives function much like a history book: past atmospheric conditions and environmental changes are recorded in their layers,” explained Dr Azzurra Spagnesi of Ca’ Foscari University of Venice, who led the study. “Alpine glaciers offer a unique opportunity to investigate the critical transition between pre-industrial and industrial times, because of their proximity to human settlements.”
Tracing Medieval Industry in Ice
Researchers of the Ca’ Foscari University of Venice and the Austrian Academy of Science drill an ice core at Weißseespitze, Ötztal Alps, in 2018. Photograph by Prof Andrea Fischer.
By examining trace elements trapped in the ice, researchers were able to identify periods of increased pollution tied to human activity. While much of the record reflects natural sources such as dust, sea salt, and biological emissions, distinct peaks in metals point to intensified mining and smelting during the Middle Ages.
“Between 700 and 1200 CE, lead and other metals showed very low concentrations, reflecting the regional background of a mostly unpolluted pre-industrial environment,” Spagnesi noted. “From roughly 950 CE onward, peaks in arsenic, lead, copper, and silver appear, corresponding to periods of intensified medieval mining and smelting in the Alps and other European regions.”
These chemical signals align with known mining regions across Europe, including the Alps and areas as far as the Harz Mountains in Germany. Although these activities were far smaller in scale than later industrial pollution, they were still significant enough to leave a lasting imprint in the glacier record.
Overall, however, human contributions remained relatively modest. The analysis shows that natural sources dominated the atmospheric composition, with anthropogenic pollution forming only a small fraction of the total signal. Instead of overwhelming the environment, medieval emissions appear as intermittent spikes against a largely stable natural background.
Fire, Climate, and Human Activity
Woodcut from a 16th-century copy of De re metallica showing the smelting of ore.
The ice core also reveals a striking period of environmental change between roughly 900 and 1200 CE. During this time, the researchers detected elevated levels of combustion markers alongside increased metal concentrations.
To better understand this pattern, the team compared the ice core data with peat samples from a nearby mountain peat bog. Both records show peaks in evidence for burning, indicating that fires became more frequent and intense during this period.
“The elevated fire signal we observe during the roughly century-long drought between about 950 and 1040 CE is likely the result of several interacting factors,” said Spagnesi. “Such dry conditions can promote cycles of vegetation growth followed by desiccation, creating highly flammable landscapes that are more prone to burning. At the same time, human activity in Alpine regions appears to have intensified. Historical and paleoenvironmental evidence points to increased grassland management, agricultural expansion, and land clearing, all of which commonly involved fire. Periods of conflict may have contributed locally, either through deliberate burning or accidental ignitions.”
The study connects these developments to broader climatic trends, including the Medieval Warm Period, when warmer and drier conditions affected much of Europe. Together, climate and human activity created a feedback loop that amplified both fire frequency and atmospheric pollution.
A Long-Term Environmental Record
One of the most significant aspects of the research is its ability to place medieval pollution in a much longer timeline. The Weißseespitze ice core preserves a record stretching back to the Roman era, allowing scientists to compare different periods of human impact.
Despite detectable traces of mining and metalworking, the medieval atmosphere remained largely dominated by natural processes. Even sulphate levels linked to human activity—such as biomass burning and early smelting—were far lower than those seen after the onset of industrialisation.
This highlights a key contrast: while medieval societies did influence their environment, their impact was episodic and regional, rather than global.
A Disappearing Archive
The summit of Weißseespitze in 2023. The dark surface shows significant melting. Photo by Prof Andrea Fischer.
The study also carries an urgent warning. When researchers returned to the site in 2025, they found that the glacier had shrunk dramatically. Ice thickness at the drilling location had dropped from nearly ten metres to just 5.5 metres.
This loss means that parts of the historical record—especially more recent layers—have already vanished.
“Glaciers in the Ötztal Alps are projected to disappear within the coming decades,” Spagnesi warned. “If glaciers disappear, the chemical and physical information they contain will be lost forever, leaving gaps in our understanding of past climate variability.”
For historians and scientists alike, the stakes are high. These alpine ice cores offer a rare window into how medieval societies interacted with their environment—capturing evidence of mining, agriculture, and climate in a single, continuous archive.
The article, “New chemical signatures from Weißseespitze ice cores (Eastern Alps): pre-industrial pollution traces from Roman Empire to early modern period,” by Azzurra Spagnesi, David Wachs, Pascal Bohleber, Elena Barbaro, Matteo Feltracco, Daniela Festi, Klaus Oeggl, Jacopo Gabrieli, Werner Aeschbach, Markus Oberthaler, Martin Stocker-Waldhuber, Andrea Gambaro, Carlo Barbante and Andrea Fischer, is published in Frontiers in Earth Science. Click here to read it.
Ice high in the Alps has preserved a surprising record of medieval industry, showing that pollution from mining and metalworking left a measurable mark on the atmosphere long before the modern age.
In a new study published in Frontiers in Earth Science, researchers analysed an ice core taken from the Weißseespitze glacier on the Austrian–Italian border. Stretching nearly ten metres down to bedrock, the core captures a continuous environmental record spanning from the Roman period to the early modern era.
“These remarkable climate archives function much like a history book: past atmospheric conditions and environmental changes are recorded in their layers,” explained Dr Azzurra Spagnesi of Ca’ Foscari University of Venice, who led the study. “Alpine glaciers offer a unique opportunity to investigate the critical transition between pre-industrial and industrial times, because of their proximity to human settlements.”
Tracing Medieval Industry in Ice
By examining trace elements trapped in the ice, researchers were able to identify periods of increased pollution tied to human activity. While much of the record reflects natural sources such as dust, sea salt, and biological emissions, distinct peaks in metals point to intensified mining and smelting during the Middle Ages.
“Between 700 and 1200 CE, lead and other metals showed very low concentrations, reflecting the regional background of a mostly unpolluted pre-industrial environment,” Spagnesi noted. “From roughly 950 CE onward, peaks in arsenic, lead, copper, and silver appear, corresponding to periods of intensified medieval mining and smelting in the Alps and other European regions.”
These chemical signals align with known mining regions across Europe, including the Alps and areas as far as the Harz Mountains in Germany. Although these activities were far smaller in scale than later industrial pollution, they were still significant enough to leave a lasting imprint in the glacier record.
Overall, however, human contributions remained relatively modest. The analysis shows that natural sources dominated the atmospheric composition, with anthropogenic pollution forming only a small fraction of the total signal. Instead of overwhelming the environment, medieval emissions appear as intermittent spikes against a largely stable natural background.
Fire, Climate, and Human Activity
The ice core also reveals a striking period of environmental change between roughly 900 and 1200 CE. During this time, the researchers detected elevated levels of combustion markers alongside increased metal concentrations.
To better understand this pattern, the team compared the ice core data with peat samples from a nearby mountain peat bog. Both records show peaks in evidence for burning, indicating that fires became more frequent and intense during this period.
“The elevated fire signal we observe during the roughly century-long drought between about 950 and 1040 CE is likely the result of several interacting factors,” said Spagnesi. “Such dry conditions can promote cycles of vegetation growth followed by desiccation, creating highly flammable landscapes that are more prone to burning. At the same time, human activity in Alpine regions appears to have intensified. Historical and paleoenvironmental evidence points to increased grassland management, agricultural expansion, and land clearing, all of which commonly involved fire. Periods of conflict may have contributed locally, either through deliberate burning or accidental ignitions.”
The study connects these developments to broader climatic trends, including the Medieval Warm Period, when warmer and drier conditions affected much of Europe. Together, climate and human activity created a feedback loop that amplified both fire frequency and atmospheric pollution.
A Long-Term Environmental Record
One of the most significant aspects of the research is its ability to place medieval pollution in a much longer timeline. The Weißseespitze ice core preserves a record stretching back to the Roman era, allowing scientists to compare different periods of human impact.
Despite detectable traces of mining and metalworking, the medieval atmosphere remained largely dominated by natural processes. Even sulphate levels linked to human activity—such as biomass burning and early smelting—were far lower than those seen after the onset of industrialisation.
This highlights a key contrast: while medieval societies did influence their environment, their impact was episodic and regional, rather than global.
A Disappearing Archive
The study also carries an urgent warning. When researchers returned to the site in 2025, they found that the glacier had shrunk dramatically. Ice thickness at the drilling location had dropped from nearly ten metres to just 5.5 metres.
This loss means that parts of the historical record—especially more recent layers—have already vanished.
“Glaciers in the Ötztal Alps are projected to disappear within the coming decades,” Spagnesi warned. “If glaciers disappear, the chemical and physical information they contain will be lost forever, leaving gaps in our understanding of past climate variability.”
For historians and scientists alike, the stakes are high. These alpine ice cores offer a rare window into how medieval societies interacted with their environment—capturing evidence of mining, agriculture, and climate in a single, continuous archive.
The article, “New chemical signatures from Weißseespitze ice cores (Eastern Alps): pre-industrial pollution traces from Roman Empire to early modern period,” by Azzurra Spagnesi, David Wachs, Pascal Bohleber, Elena Barbaro, Matteo Feltracco, Daniela Festi, Klaus Oeggl, Jacopo Gabrieli, Werner Aeschbach, Markus Oberthaler, Martin Stocker-Waldhuber, Andrea Gambaro, Carlo Barbante and Andrea Fischer, is published in Frontiers in Earth Science. Click here to read it.
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